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  • Architect vs Design and Build Company: Which is Best for Your Extension?

    Architect vs Design and Build Company: Which is Best for Your Extension?

    One of the biggest decisions homeowners face when planning an extension or loft conversion is whether to hire an independent architect or go with a design and build company. Both options have genuine advantages — and both have pitfalls. This guide gives you an honest, clear comparison so you can make the right choice for your project.

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    What’s the Difference?

    Independent Architect Route

    You hire an architect (separately from your builder) to design your project, obtain planning permission, produce technical drawings, and potentially manage the construction phase. You then separately appoint a builder, usually after a competitive tender process managed by your architect.

    Design and Build Route

    A single company handles both the design and the construction. They produce the drawings, submit for planning, and build it themselves (or with their own subcontractors). One contract, one point of contact, one invoice.

    The Case for an Independent Architect

    1. Design Quality

    Independent architects are incentivised purely on design quality — they’re not trying to make construction easier or cheaper. They will push harder for better spatial planning, natural light, and architectural character. The best residential extensions in the UK are almost always designed by independent architects.

    2. You Control the Builder Selection

    With an independent architect, you go out to tender — multiple builders quote against the same drawings. This creates genuine competition that typically saves 10–20% on build cost versus a design and build company where the builder sets their own price. Your architect advises on which tender to accept.

    3. Independent Oversight of Construction

    When your architect oversees construction, they are working for you — their professional duty is to you, not to the builder. They will snag issues, query non-compliant work, and certify payments only when works are properly completed. This independent oversight is a significant protection.

    4. Stronger Planning Outcomes

    Experienced residential architects often have better relationships with planning departments and a track record of approved applications for your specific building type and area. For complex planning situations (conservation areas, listed buildings, Article 4 areas), a specialist architect is significantly better placed than a generalist design and build company.

    5. Professional Accountability

    Registered architects are regulated by the Architects Registration Board (ARB) and face professional sanctions if they breach their code of conduct. They carry professional indemnity insurance. This gives you legal recourse if something goes wrong with the design.

    The Case for Design and Build

    1. Simplicity

    One contract, one company to deal with. You don’t need to separately manage an architect and a builder. Coordination happens internally. For busy homeowners who want to be hands-off, this is genuinely appealing.

    2. Speed

    Because the same company designs and builds, they can start ordering materials and planning site logistics before the planning application is even submitted. The handover from design to build is seamless. Total project time from instruction to completion can be faster with a good design and build company.

    3. Single Point of Responsibility

    If something goes wrong, there’s no finger-pointing between architect and builder about whose fault it is. The design and build company is liable for both the design and the construction under a single contract. This can simplify dispute resolution.

    4. Price Certainty (Sometimes)

    Some design and build companies offer a fixed price from the outset. Whether this is genuinely advantageous depends on the quality of the specification — a vague specification can lead to disputed variations. But when the specification is rigorous and the price is fixed, it can provide budget certainty.

    The Risks of Design and Build

    Design and build is not without significant risks that homeowners often overlook:

    Conflict of Interest in Design Decisions

    When the same company designs and builds, there’s an inherent incentive to design what’s easiest and cheapest to build, not what’s best for you. Specification choices, structural solutions, and material selections may be influenced by what’s most profitable for the contractor rather than what’s best for your home.

    No Independent Oversight

    There is no independent professional checking the quality of construction on your behalf. The only way to have independent oversight in a design and build contract is to separately appoint a project manager or employer’s agent — which adds cost and partially defeats the simplicity argument.

    Design Quality Can Suffer

    Design and build companies typically employ architectural technicians rather than architects, and their design process is driven by buildability rather than architectural quality. The result is often functional but rarely exceptional. If maximising the architectural quality and long-term value of your home matters to you, independent architecture is usually better.

    Higher Cost Can Masquerade as Lower Cost

    Design and build companies often quote an all-in price that looks cheaper than “architect fee + builder quote.” But the design fee is cross-subsidised into the build price, and without competitive tendering there’s no market check on whether the build price is fair. Many homeowners discover after the fact that they paid 15–25% more than they would have through the traditional route.

    When to Choose an Independent Architect

    • Your project is complex (conservation area, listed building, structural challenges)
    • Design quality matters to you and you want to maximise your home’s value
    • You want competitive builder pricing
    • You want independent oversight of the construction
    • You’re in London with complex planning requirements
    • Your budget is significant and you want professional accountability throughout

    When Design and Build Might Make Sense

    • Your project is standard and straightforward (simple single-storey extension in a non-conservation area)
    • You prioritise speed and simplicity over design optimisation
    • You have very limited time to manage an architect/builder relationship
    • You’ve found a reputable design and build company with strong references for exactly your project type

    Cost Comparison

    It’s difficult to give precise figures because projects vary enormously. But as a general guide for a typical London loft conversion (£120,000 build cost):

    RouteTypical Total CostNotes
    Independent architect + competitive tender£128,000–£135,000Architect fee (£8–12k) + competitive build
    Design and build company£135,000–£150,000Higher build cost due to no competition

    The independent route often comes out cheaper overall and delivers better design quality — but requires more involvement from you in the process.

    Frequently Asked Questions

    Is design and build more expensive than using an architect?

    Often yes, when you factor in the full cost comparison. Design and build companies embed their design costs into the build price, and without competitive tendering you can’t benchmark whether the build price is fair. However, for very simple projects, the simplicity premium can be worth it.

    Can I use a design and build company for a loft conversion?

    Yes, and many people do. Loft conversions are relatively standardised in terms of construction, which suits the design and build model. However, for complex conversions (mansard, hip-to-gable) or where planning permission is needed in a conservation area, an experienced independent architect is often better placed.

    What contract should I use with a design and build company?

    Use an industry-standard contract — the JCT Design and Build Contract (DB 2024) or the shorter JCT Minor Works Building Contract if the project is below £150k. Avoid bespoke contracts written by the contractor — they will invariably favour the contractor’s interests.

    Can Crown Architecture act as both architect and project manager?

    Yes — we offer full-service packages that include design, planning, structural coordination, tender management, and construction oversight. This gives you the design quality of independent architecture with significantly reduced management burden on your part.

    What questions should I ask a design and build company before hiring?

    Ask: What qualifications does your designer hold (architect vs. architectural technician)? Can I speak to 3 clients with a similar project who completed in the last 12 months? What’s your planning approval rate? What does your contract say about variations? Are you a member of the Federation of Master Builders or similar body?

    Talk to Crown Architecture About Your Project

    At Crown Architecture & Structural Engineering Ltd, we offer a full-service approach that combines the best of both worlds — professional architectural design and planning expertise, with coordinated structural engineering and construction management support. We have exceptional planning approval rates across all London boroughs and genuine client references for every project type. Call us on 07443804841 or complete the form above.

  • Kitchen Extension Planning Permission UK 2025: Do You Need It?

    Kitchen Extension Planning Permission UK 2025: Do You Need It?

    The kitchen is the most popular room in the UK for extending — and for good reason. A well-designed kitchen extension transforms how a family lives and almost always adds more value than it costs. But one of the first questions homeowners ask is: do I need planning permission for a kitchen extension? The answer depends on several factors, and this guide explains all of them clearly.

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    The Short Answer

    Many kitchen extensions in England can be built under Permitted Development Rights — meaning you don’t need a full planning application. However, there are strict size and design conditions you must meet. If your extension exceeds these limits, is in a conservation area, or affects a listed building, you will need planning permission.

    Permitted Development Rules for Kitchen Extensions (England 2025)

    The key rules under Class A of the General Permitted Development Order (GPDO) for single-storey rear extensions (where most kitchen extensions fall) are:

    Rear Extension Depth Limits

    • Detached house — Up to 4 metres deep beyond the original rear wall
    • Semi-detached or terraced house — Up to 3 metres deep beyond the original rear wall

    Under the Neighbour Consultation Scheme (the “prior approval” process), these limits can extend to 8 metres (detached) and 6 metres (semi/terraced) — but only with prior approval from the local planning authority, and only if no neighbours object.

    Height Restrictions

    • Maximum height: 4 metres overall
    • If within 2 metres of a boundary: maximum eaves height 3 metres

    Materials

    The extension must be built in materials that are “similar in appearance” to the existing house. A brick extension on a rendered house or vice versa may be acceptable, but drastically different materials may require a planning application.

    Coverage

    The total area of all extensions and outbuildings must not exceed 50% of the total area of the original curtilage (garden) of the property.

    No Verandas or Raised Platforms

    The extension cannot include a veranda, balcony, or raised platform — these always require planning permission.

    When Does a Kitchen Extension Need Planning Permission?

    You will always need planning permission if:

    • Your extension exceeds the size limits above
    • The property is a listed building (Listed Building Consent required)
    • The property is in a conservation area and the extension is visible from a highway
    • The property is subject to an Article 4 Direction removing Permitted Development rights (common in many London boroughs)
    • Permitted Development rights were removed by a planning condition on the original planning permission
    • The property is a flat or maisonette (flats have different, more restrictive PD rights)

    London Specifically: A Different Set of Rules

    London homeowners need to be especially careful. Many London boroughs have Article 4 Directions covering large parts of their residential areas — particularly:

    • Islington — extensive Article 4 areas covering most Victorian terraced properties
    • Camden — large conservation areas covering many residential streets
    • Hackney — Permitted Development restricted in designated areas
    • Westminster, Kensington & Chelsea — most of the borough is conservation area
    • Southwark, Lambeth — significant conservation area coverage

    Even if your house is not in a conservation area, a previous planning condition on your property may have removed Permitted Development rights. Check your original planning permission documents or ask your council’s planning department.

    What About a Side Return Kitchen Extension?

    Side return extensions — filling in the narrow gap between a Victorian terraced house and its boundary wall — are extremely popular in London. The Permitted Development rules are slightly different for extensions at the side:

    • Maximum width: 50% of the width of the original house
    • Maximum height: 4 metres (3 metres if within 2 metres of boundary)

    However, if the side return faces a highway (not just the back garden), it almost always needs planning permission regardless of size. In conservation areas, side return extensions almost always require planning permission.

    What About Wrap-Around Extensions?

    A wrap-around extension combines a rear extension and a side return into one L-shaped structure. These are generally not possible under Permitted Development and typically require a planning application, because the side element is visible from the highway and the combined volume often exceeds PD limits. Most London architects will apply for planning permission for wrap-arounds as standard.

    Does a Kitchen Extension Need Building Regulations?

    Yes — all extensions require Building Regulations approval regardless of whether they need planning permission. Building Regulations cover structural safety, fire safety, thermal performance (energy efficiency), drainage, and ventilation. You must notify your local Building Control department before construction begins.

    Your architect will typically prepare Building Regulations drawings as part of their service, and your structural engineer will provide calculations. Don’t confuse Permitted Development (planning) with Building Regulations — they are entirely separate processes.

    The Planning Application Process for Kitchen Extensions

    If you do need planning permission, here’s what to expect:

    1. Pre-Application Advice (Optional but Recommended)

    Many councils offer a paid pre-application advice service (typically £100–£300). Your architect sends preliminary designs to the planning officer, who gives informal feedback before the formal application. This can significantly improve approval chances.

    2. Full Planning Application

    Your architect prepares and submits the planning application including: application form, site location plan, existing and proposed drawings (plans, elevations, sections), and a design & access statement (for some applications). The planning fee for a householder application is currently £258 in England (as of late 2024).

    3. Decision

    The statutory determination period is 8 weeks. In practice, many London boroughs take 10–12 weeks. Complex or contentious applications can take longer.

    How Much Does a Kitchen Extension Cost?

    Build costs vary significantly by location and specification. In London 2025:

    • Small kitchen extension (15m²): £30,000–£45,000
    • Medium kitchen extension (20–25m²): £45,000–£70,000
    • Large rear or side return extension (25–40m²): £70,000–£130,000
    • Wrap-around extension: £90,000–£180,000+

    Kitchen fit-out (units, worktops, appliances) is additional to the build cost. Budget £10,000–£40,000 for a mid-to-high specification kitchen in London.

    Frequently Asked Questions

    Can I build a 6-metre kitchen extension without planning permission?

    On a detached house, yes — under the Neighbour Consultation Scheme (prior approval process), up to 8 metres is possible. On a semi-detached or terraced house, up to 6 metres with prior approval. However, if any neighbour objects, the council will assess the impact and may require planning permission.

    Do I need planning permission for a kitchen extension in a conservation area?

    Probably yes, if the extension is visible from a highway (including any public footpath). Rear extensions not visible from a public road may still be under Permitted Development, but you must confirm with your local authority. Conservation area extensions are assessed more carefully.

    How long does planning permission last?

    Planning permission is valid for 3 years from the date of grant. You must start construction within this period (though you don’t need to complete it).

    Can a flat have a kitchen extension?

    Flats and maisonettes have very limited Permitted Development rights — generally none for extensions. Any extension to a flat would almost certainly require planning permission, and in many cases (particularly in converted houses) would be practically impossible without the freeholder and other leaseholders agreeing.

    Is a lean-to kitchen extension Permitted Development?

    Yes — a lean-to single-storey rear extension can be Permitted Development provided it meets the size, height, and materials requirements. The lean-to roof (typically a monopitch or shallow pitch) must not exceed 4 metres overall height.

    What is a Lawful Development Certificate and do I need one?

    A Lawful Development Certificate (LDC) is a formal certificate from the planning authority confirming that your proposed extension is lawful under Permitted Development. It’s not legally required, but is highly recommended — it’s valuable evidence if you sell the property, and provides peace of mind that the extension is definitely legal. Cost: approx. £103 (householder LDC fee in England).

    Can my architect deal with planning for me?

    Yes — preparing and submitting a planning application is a standard part of an architect’s service. They will prepare all required drawings, fill in the application form, pay the planning fee, and act as the agent liaising with the planning officer on your behalf.

    Get Planning Permission Help for Your Kitchen Extension

    Crown Architecture & Structural Engineering Ltd specialises in kitchen extensions across all London boroughs. We know each borough’s planning policies, conservation area requirements, and Article 4 restrictions — and we have an exceptional planning approval rate. Call us on 07443804841 or complete the form above for a free consultation.

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  • How to Find a Good Architect in London: The Complete 2025 Guide

    How to Find a Good Architect in London: The Complete 2025 Guide

    Finding a good architect in London is one of the most important decisions you’ll make for your home extension, loft conversion, or renovation project. The right architect will save you money, navigate planning permission smoothly, and deliver a result that genuinely adds value to your home. The wrong one will cost you months of delays and thousands in wasted fees. This guide tells you exactly how to find the right person for your project.

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    What Does an Architect Actually Do for You?

    Before searching for an architect, it helps to be clear about what you’re actually hiring them for. At its core, an architect provides:

    • Design — Transforming your brief into a workable, beautiful design for your home
    • Planning drawings — Producing drawings to submit for planning permission (where required) or Permitted Development sign-off
    • Technical drawings — Producing detailed construction drawings for builders to work from
    • Building Regulations coordination — Producing drawings that meet Building Control requirements, working with structural engineers
    • Project management (if you choose a full service) — Tendering to builders, overseeing construction, certifying payments

    Not every architect offers every service. Some work purely on design and planning drawings. Others offer end-to-end project management. Know which level of service you need before you start searching.

    Step 1: Define Your Brief Before Searching

    The clearest briefs attract the best architects. Before you start contacting anyone, write down:

    • What type of project is it? (loft conversion, rear extension, side extension, full renovation)
    • What’s your approximate budget for construction? (not the architect fees — the build cost)
    • What planning situation do you have? (Permitted Development, full planning required, conservation area, listed building)
    • What’s your timeline?
    • What outcome matters most — maximising space, adding value, improving quality of life?

    Architects who respond to a clear brief are significantly more likely to deliver well. And a clear brief lets you compare quotes fairly.

    Step 2: Where to Find Architects in London

    RIBA Find an Architect

    The Royal Institute of British Architects (RIBA) operates a free directory at architecture.com/find-an-architect. Every RIBA-registered architect has met minimum education and professional standards. You can filter by location, project type, and firm size. This is the most reliable starting point for finding vetted architects in London.

    ARB Register

    The Architects Registration Board (ARB) is the statutory regulator of architects in the UK. Only people registered with the ARB can call themselves an “architect.” You can check if someone is registered at arb.org.uk. Always verify registration before hiring.

    Personal Recommendations

    The best leads often come from neighbours who’ve had work done recently. Walk around your area and knock on the door of a house where you admire the extension or loft conversion. Ask who designed it. People who’ve had excellent architects are usually delighted to recommend them.

    Google Search (With Caution)

    Searching “architect loft conversion Hackney” or “house extension architect Islington” will surface many results. Be aware that ranking highly on Google does not guarantee quality — it just means a firm invests in SEO. Always check reviews on Google Maps, Houzz, and any portfolio examples before contacting.

    Houzz

    Houzz is an interior design and architecture platform with photo portfolios and client reviews. It’s particularly good for assessing the visual quality of an architect’s work — you can browse projects similar to yours and find the architect directly from their project photos.

    Step 3: How to Vet Architects — What to Ask

    Once you have a shortlist of 3–5 architects, have an initial conversation (most offer a free 30-minute consultation) and ask these questions:

    Experience with Your Project Type

    “How many loft conversions / rear extensions / [project type] have you designed in the past year?” An architect who regularly does your type of project will be faster, more accurate with costs, and better at anticipating planning issues. A general practice that mainly does commercial work may struggle with residential planning nuances.

    Local Planning Experience

    “Have you worked with [your borough’s] planning department before?” London has 33 planning authorities, each with different priorities, conservation area policies, and officers with different preferences. An architect who has recent experience with your specific borough is a significant advantage.

    Planning Success Rate

    “What’s your planning application approval rate?” A well-regarded residential architect in London should be achieving 85–95%+ first-time approval. If they’re hedgy about this, probe further.

    References

    “Can I speak to 2–3 recent clients who had a similar project?” Any reputable architect should be able to provide references. If they’re reluctant or can’t produce any, that’s a red flag.

    Structural Engineering Coordination

    “Do you work with a structural engineer, and is this included in your fee or separate?” Most residential projects need a structural engineer. Architects who have an established structural engineering partner (or offer structural services in-house) will save you significant coordination time and cost.

    Step 4: Understanding Architect Fees in London

    Architect fees in London are typically quoted in one of three ways:

    Percentage of Construction Cost

    Traditional approach. Residential architects typically charge 8–15% of construction cost for full service (design through to construction completion). For partial services (planning drawings only), expect 3–6%. On a £150,000 loft conversion, a full-service fee might be £12,000–£22,500.

    Fixed Fee

    Increasingly common for residential projects. The architect quotes a fixed sum for defined deliverables. Good for budget certainty. Make sure the fee proposal clearly defines what’s included at each stage.

    Hourly Rate

    Less common for residential projects but sometimes used for consultancy or advice. London architect hourly rates: £75–£200 per hour depending on seniority and firm size.

    Step 5: Red Flags to Watch Out For

    • Not ARB-registered — Anyone calling themselves an “architect” who isn’t on the ARB register is committing an offence under the Architects Act 1997.
    • No professional indemnity insurance — Always ask for confirmation of PI insurance. Without it, you have no recourse if their design error causes a costly problem.
    • No written fee agreement — Always get a written scope of services and fee schedule before any work begins.
    • Unrealistically low fees — An architect quoting significantly below market rate is likely cutting corners somewhere — whether in the design quality, the time spent on your project, or their level of professional cover.
    • Vague about what’s included — “We’ll sort out the planning” without clarity on what drawings will be produced, who manages the application, and what happens if it’s refused is not acceptable.
    • No experience with your borough — Conservation area, Article 4 direction, and other local policies require specific knowledge. A generic residential architect without local knowledge may produce inappropriate applications that get refused.

    RIBA-Registered vs. Architectural Designer: What’s the Difference?

    In the UK, only those registered with the ARB can use the title “architect.” However, many people offering architectural design services are not registered architects — they may call themselves “architectural designers,” “architectural technicians,” or “architectural consultants.”

    This doesn’t automatically mean they’re lower quality. Some highly experienced architectural technicians (MCIAT) do excellent residential work. However, for complex projects, conservation areas, or listed buildings, a fully qualified and registered architect offers greater depth of knowledge and professional accountability.

    Frequently Asked Questions

    How much does an architect cost in London for a loft conversion?

    For planning and working drawings for a loft conversion in London, expect to pay £3,000–£8,000 for a typical project. Full service including project management runs £8,000–£15,000+. See our full guide: How Much Does an Architect Cost in London?

    Do I need a RIBA architect or will any architectural designer do?

    For most standard residential projects, a competent architectural designer can produce adequate planning drawings. However, for listed buildings, complex conservation area projects, or high-value properties where design quality matters, a fully RIBA-registered architect offers higher standards and greater professional protection.

    How long does it take to find and hire an architect?

    Allow 2–4 weeks from initial contact to a signed fee agreement. Good architects in London are often booked 2–4 weeks out from being able to start work. Factor this into your project timeline.

    Should I hire an architect who’s done projects in my specific street?

    It helps but isn’t essential. What matters more is experience with your borough’s planning department and the architectural style of your building type (Victorian terrace, 1930s semi, Edwardian villa etc.). Local knowledge of planning officers and precedents is more valuable than hyperlocal project history.

    Can an architect also manage the build?

    Yes. Architects who offer a “full service” or “contract administration” service will manage the tender process (getting builders to quote), oversee the build, certify payments, and handle any disputes. This typically adds 3–5% to their fee but can save significantly more in builder disputes and cost overruns.

    What questions should I ask in the first meeting with an architect?

    Ask about: their planning approval rate, experience with your project type and borough, what structural engineering provision they offer, their fee structure, typical project timelines, and request to see 3–5 examples of similar completed projects with client references.

    Is it worth hiring a local architect versus a larger national firm?

    For most residential work in London, local knowledge and accessibility matter more than firm size. A local practice with strong relationships with your borough’s planning officers and proven experience on Victorian and Edwardian properties will often outperform a large national firm with less local context.

    Talk to Crown Architecture About Your Project

    Crown Architecture & Structural Engineering Ltd is a London-based architectural practice specialising in residential extensions, loft conversions, and structural engineering across all London boroughs. We’re ARB-registered, carry full professional indemnity insurance, and have completed hundreds of residential projects across Hackney, Islington, Lambeth, Southwark, Wandsworth, and beyond.

    Call us on 07443804841 or complete the form above — we offer a free 30-minute consultation for all new projects.

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  • Structural Engineer Costs UK 2025: Fees, What’s Included & How to Choose

    Structural Engineer Costs UK 2025: Fees, What’s Included & How to Choose

    Hiring a structural engineer is one of the most important steps in any extension, loft conversion, or renovation project — yet many homeowners have no idea what to expect when it comes to fees. In this guide, we break down structural engineer costs across the UK for 2025, explain exactly what you get for your money, and help you avoid overpaying.

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    How Much Does a Structural Engineer Cost in the UK?

    Structural engineer fees vary widely depending on the type and complexity of the work. Here are typical 2025 costs for the most common residential projects:

    ServiceTypical Cost
    Structural survey / report (basic)£300 – £600
    RSJ beam calculations (1 beam)£250 – £500
    Loft conversion structural calculations£500 – £900
    Single-storey extension calculations£600 – £1,200
    Two-storey extension calculations£900 – £1,800
    Chimney breast removal calculations£400 – £750
    Basement conversion structural design£1,500 – £3,500
    Full structural engineering service (large project)£2,000 – £6,000+

    London and South East: Expect fees approximately 20–30% higher than the national average, due to higher overheads and greater demand. A structural engineer in London typically charges £350–£700 for RSJ calculations versus £250–£500 in other regions.

    What Affects Structural Engineer Fees?

    1. Project Complexity

    A simple RSJ beam to create an open-plan kitchen is a fraction of the cost of designing the structural frame for a two-storey rear extension. The more complex the loading, the more engineering hours are required.

    2. Location

    London-based structural engineers command higher fees than those in the Midlands or North of England. However, many London firms now offer remote structural calculations services, where you upload drawings and they work off them — sometimes at lower rates than traditional local firms.

    3. Level of Service Required

    There’s a significant difference between:

    • Calculations only — Engineer provides a written report with structural calculations for Building Control submission. No site visits.
    • Calculations + drawings — Includes structural layout drawings showing beam positions, pad foundations, lintels etc. More expensive but often required by Building Control.
    • Full structural design service — Calculations, drawings, specification, site inspections, Building Control liaison. Best for complex or high-value projects.

    4. Speed of Service

    Standard turnaround is typically 1–3 weeks. If you need urgent calculations (within 48–72 hours), most engineers charge a premium of 25–50% on top of their standard fee.

    Common Structural Engineering Services & What They Cost

    RSJ Steel Beam Calculations (Structural Beam Design)

    The most common residential structural engineering request. When you remove a load-bearing wall to create open-plan living or widen an opening, you need an RSJ (or flitch beam) specified by a structural engineer. Costs: £250–£500 nationally, £350–£700 in London.

    This includes the engineer calculating the required beam size (in kg/m), pad foundation designs where needed, and producing a written report accepted by Building Control. Most engineers turn this around in 3–7 days.

    Loft Conversion Structural Calculations

    A loft conversion requires structural calculations covering:

    • New floor (to carry bedroom live loads)
    • Alterations to the existing roof structure (cutting rafters, installing a steel ridge beam where needed)
    • Dormer framing (if applicable)
    • New staircase opening through existing ceiling/floor

    Typical costs: £500–£900. For hip-to-gable or mansard conversions that involve significant structural alterations, expect £800–£1,200+.

    Rear or Side Extension Structural Calculations

    A single-storey rear extension typically requires foundation design (strip foundations or piled foundations on London clay), calculations for the new roof structure, and any new RSJ beams where the extension opens into the existing house. Costs: £600–£1,200.

    Two-storey extensions are more complex — the structural engineer must consider additional floor loadings, more complex foundation requirements, and any party wall considerations. Costs: £900–£2,000+.

    Chimney Breast Removal

    Removing a chimney breast on the ground, first or second floor requires a steel gallows bracket or padstone + RSJ combination to carry the weight of the chimney above. A structural engineer must specify this correctly or the structure could become dangerous. Costs: £400–£750 for the structural report and calculations.

    Basement Conversion Structural Design

    Basement projects are significantly more complex — involving underpinning, waterproofing design, tanking specifications, and retaining wall design. Structural engineering fees for a basement project start at £1,500 and can exceed £5,000 for complex London properties. Many engineers specialising in basements also charge for site visits (£200–£400 per visit).

    Do You Always Need a Structural Engineer?

    For any structural work, the answer is almost always yes. Building Control will not sign off work without structural calculations from a qualified structural engineer (or a chartered civil engineer) in most cases. The exceptions are very minor works where standard construction details apply — but even then, experienced builders will often recommend getting calculations to protect both the homeowner and themselves.

    Situations where you must have a structural engineer:

    • Removing a load-bearing wall
    • Creating a new opening (window, door, or passageway) in a load-bearing wall
    • Loft conversions (always)
    • Extensions (always — for foundation design at minimum)
    • Chimney breast removal
    • Underpinning or basement work
    • Flat conversions and structural alterations to existing buildings

    Structural Engineer vs Architect: Who Do You Need?

    Many homeowners confuse the roles of structural engineers and architects. Here’s the key distinction:

    • Architect — Designs the layout, aesthetics, and function of a space. Produces planning drawings and working drawings. Manages the project design process.
    • Structural engineer — Calculates the structural integrity of the design. Specifies beams, foundations, and load-bearing elements. Ensures the building won’t fall down.

    For most residential projects, you need both. Your architect designs the extension or conversion; your structural engineer makes sure it will stand safely. Many architectural practices (including Crown Architecture) work with trusted structural engineers as part of an integrated service — meaning you don’t need to find and manage a structural engineer separately.

    How to Find and Choose a Structural Engineer in the UK

    Check Their Qualifications

    Look for membership of the Institution of Structural Engineers (IStructE) — indicated by the letters MIStructE or FIStructE after their name. Alternatively, chartered civil engineers (MICE) can carry out structural engineering work. These are regulated professional bodies with strict competency requirements.

    Ask for a Written Quote

    Always get a written fee proposal before instructing a structural engineer. The quote should clearly state what’s included: whether it’s calculations only, calculations and drawings, or a full structural design service. Ask explicitly what Building Control submission documents you’ll receive.

    Check Their Experience with Similar Projects

    A structural engineer who specialises in large commercial projects may not be the best choice for a residential loft conversion. Ask if they regularly work on residential projects of similar scale and type.

    Use Your Architect’s Recommendation

    The best way to find a reliable structural engineer is through your architect. Architects who work with the same structural engineers regularly develop efficient working relationships — which means fewer delays, cleaner coordination between architectural and structural drawings, and fewer surprises on site.

    Is It Worth Getting Multiple Quotes?

    Yes — structural engineering fees can vary considerably. It’s worth getting 2–3 quotes for any project. However, don’t choose purely on price. A structural engineer who is £100 cheaper but slow, hard to reach, or whose calculations get rejected by Building Control will cost you far more in delays.

    Key factors to compare: fee, turnaround time, what documents are included, whether they’ll liaise directly with Building Control if queries arise.

    Frequently Asked Questions

    How much does a structural report cost UK?

    A basic structural report (for a single beam or simple load-bearing wall removal) costs £300–£600 nationally, rising to £400–£800 in London. More complex projects with multiple elements cost proportionally more.

    Can I use any structural engineer or do they need to be local?

    For most calculations-based work, the structural engineer does not need to visit site — they work from architect drawings and a few standard measurements. You can use engineers anywhere in the UK. However, for site inspections (which some projects require), a local engineer is more practical.

    How long does it take to get structural calculations?

    Standard turnaround is 1–3 weeks. Urgent same-week service is usually available for a fee premium of 25–50%. Complex projects (basements, two-storey extensions) may take longer.

    Do I need a structural engineer for a single-storey extension?

    Yes. Building Control requires structural calculations for all extensions to demonstrate the foundations, walls, and roof meet current standards. This is non-negotiable regardless of whether the extension is under Permitted Development or requires a planning application.

    Can my architect also act as structural engineer?

    No — unless your architect is also a qualified structural engineer (rare). Architects and structural engineers are separate professions with different qualifications. However, many architectural practices work closely with structural engineers and can coordinate this service on your behalf.

    Are structural engineer fees tax deductible?

    For a residential property that is your home, structural engineering fees are generally not tax deductible. However, if the property is a rental investment or commercial property, professional fees may be capital expenditure that affects your Capital Gains Tax calculation — consult an accountant for your specific situation.

    What is the difference between structural calculations and structural drawings?

    Structural calculations are written mathematical documents proving that beams, foundations, and structural elements are adequately sized. Structural drawings are scaled graphical documents showing where structural elements go (beam positions, foundation depths, reinforcement layouts). Building Control may require one or both depending on the project.

    Get Structural Engineering Support for Your Project

    At Crown Architecture & Structural Engineering Ltd, we provide a fully integrated architectural and structural engineering service. Whether you need standalone structural calculations or a full design and build coordination package, our team works seamlessly to get your project to Building Control approval and on site. Call us on 07443804841 or complete the form above for a free consultation.

    Related reading:

  • L-Shaped Dormer Loft Conversion: Cost, Benefits & Planning Guide UK 2025

    The L-shaped dormer loft conversion is the go-to choice for Victorian and Edwardian terraced houses across London and the rest of the UK. It combines two dormer structures — one at the back of the main roof and one on the rear outrigger (back addition) — to create a maximum-area L-shaped floor plan in the loft that can accommodate two bedrooms, a bathroom, and sometimes even more.

    At Crown Architecture, the L-shaped dormer is one of our most popular loft conversion types — and for good reason. This guide explains exactly how it works, how much it costs in 2025, and whether your property qualifies.

    📋 Get a Free Quote

    Interested in a loft conversion or extension? We offer free initial consultations.

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    What Is an L-Shaped Dormer Loft Conversion?

    An L-shaped dormer extends the loft space over both the main rear slope of the roof AND the rear outrigger — the projecting back addition that most Victorian terraces have. The result is a large, full-height L-shaped room at loft level that can be divided into multiple rooms.

    This works because Victorian and Edwardian terraces typically have:

    • A main two or three-storey block at the front
    • A narrower single or two-storey rear outrigger (back addition) projecting into the garden

    Both the main roof and the outrigger roof pitch in the same direction — toward the rear — so a flat-roofed dormer can be constructed across both, creating a single continuous L-shaped loft floor.

    How Much Space Does an L-Shaped Dormer Create?

    An L-shaped dormer is one of the most space-efficient loft conversion types available. Depending on your property’s footprint, you can typically gain:

    • 35–55 sq m of usable floor space in a typical London Victorian terrace
    • Enough space for two double bedrooms and a bathroom as a minimum
    • Optionally, a master bedroom with en suite and walk-in wardrobe, plus a second bedroom
    • On larger properties, two bedrooms, a bathroom, and a study or nursery

    This is significantly more space than a standard rear dormer (which typically provides 20–35 sq m) — making the L-shaped conversion ideal for growing families who need to add multiple rooms in one go.

    L-Shaped Dormer Loft Conversion Cost UK 2025

    The L-shaped dormer is typically more expensive than a single rear dormer due to the greater structural complexity and additional surface area. Here are typical costs in 2025:

    Specification London (2025) National Average
    Basic L-shaped dormer (shell only) £55,000 – £75,000 £45,000 – £65,000
    Mid-range (two bedrooms + bathroom) £70,000 – £100,000 £55,000 – £85,000
    High spec (master en suite + second bedroom) £90,000 – £130,000 £75,000 – £110,000

    These prices include structural steelwork, flat roof covering (GRP or EPDM), dormer cheeks, windows, insulation, plasterboard, flooring, staircase, and first fix (electrical and plumbing rough-in). They exclude furniture, kitchen or bathroom fitting, and premium finishes.

    What Drives the Cost?

    • Steel structure: The junction between the two dormers requires a structural steel frame — typically the most significant cost driver.
    • Flat roof specification: GRP (fibreglass) is the standard choice; EPDM rubber is cheaper; sedum (green) roofs are premium.
    • Windows: The rear dormer wall is typically fitted with Juliet balcony sliding doors or a full-width window — both larger and more expensive than standard casements.
    • Bathroom specification: En suite fittings range from £3,000 (standard) to £15,000+ (luxury).
    • Staircase: L-shaped dormers require a new staircase — typically £4,000–£10,000 depending on design.

    Does an L-Shaped Dormer Need Planning Permission?

    This is one of the most common questions we receive. The answer depends on which part of London (or the UK) you’re in.

    Permitted Development in London Boroughs

    In most London boroughs, rear dormers are permitted development provided they meet the criteria set out in the Town and Country Planning (General Permitted Development) Order 2015. For a rear dormer to be PD, it must:

    • Not protrude beyond the plane of the existing roof at the front
    • Not be higher than the highest part of the existing roof
    • Not overhang the outer face of the wall
    • Not extend beyond 40 cubic metres (terraced house) or 50 cubic metres (detached/semi)
    • Not be clad in a material that is visibly different from the existing house

    The challenge with L-shaped dormers is that they span two roof sections — and some local authorities have queried whether the 40 cubic metre limit applies to both dormers combined or each individually. In most cases, the limit is applied to the overall loft extension volume.

    When Planning Permission Is Required

    • In conservation areas — dormers visible from the road require planning permission in most London conservation areas
    • In areas with Article 4 directions removing PD rights (common in inner London)
    • For listed buildings — full planning and listed building consent required
    • Where the volume limit is exceeded

    Is an L-Shaped Dormer Suitable for My Property?

    An L-shaped dormer works best on:

    • Victorian and Edwardian terraced houses with a rear outrigger
    • Properties with an outrigger roof that is at least 2.5m above the upper floor ceiling (to give usable head height in the outrigger section)
    • Properties where the rear outrigger is at least 2.5m wide
    • Properties where neighbours on both sides are not opposed (party wall matters apply)

    It is less suited to:

    • Detached or semi-detached houses without rear outriggers
    • Bungalows
    • Properties where the outrigger is very shallow (less than 2m rear to front)

    The Party Wall Act and L-Shaped Dormers

    Because the rear outrigger typically shares a party wall with your neighbour, an L-shaped dormer almost always triggers the Party Wall Act 1996. You must serve Party Wall Notices on affected neighbours before construction begins, and in some cases appoint a Party Wall Surveyor.

    Crown Architecture can advise on the party wall process and connect you with accredited party wall surveyors. Don’t skip this step — it’s a legal requirement and failing to follow it can cause delays, disputes, and even court orders to stop work.

    L-Shaped Dormer Loft Conversions Across London

    The L-shaped dormer is particularly common in inner and east London, where Victorian terraces with outriggers are abundant. We work regularly in:

    • Hackney — large Victorian terraces ideal for L-shaped dormers
    • Islington — Georgian and Victorian terraces with rear outriggers
    • Waltham Forest — Edwardian semis with substantial outrigger sections
    • Haringey — Victorian terraces in Tottenham and Wood Green

    How Much Value Does an L-Shaped Dormer Add?

    An L-shaped dormer that adds two bedrooms and a bathroom can increase a London property’s value by 20–30%. On a £600,000 home, that’s £120,000–£180,000 in added value for an investment of £70,000–£100,000 — one of the best returns available in home improvement.

    The break-even calculation is compelling: even at the high end of costs, a well-executed L-shaped dormer typically adds more value than it costs to build in most London postcodes.

    Frequently Asked Questions About L-Shaped Dormers

    How much does an L-shaped dormer loft conversion cost in London?

    An L-shaped dormer loft conversion in London typically costs between £70,000 and £100,000 for a mid-range specification with two bedrooms and a bathroom. Basic shell costs start at around £55,000; high-spec conversions can reach £130,000.

    Does an L-shaped dormer need planning permission?

    In most cases, an L-shaped dormer falls within permitted development rights and does not need planning permission. However, permission is required in conservation areas, for listed buildings, or where the volume limit is exceeded.

    What is the difference between an L-shaped dormer and a standard rear dormer?

    A standard rear dormer extends only over the main rear slope. An L-shaped dormer extends over both the main roof AND the rear outrigger, creating a larger L-shaped floor plan with significantly more space.

    How long does an L-shaped dormer loft conversion take?

    On site: 10–16 weeks. Total from instruction to completion (including design and approvals): 6–9 months.

    How much space does an L-shaped dormer create?

    Typically 35–55 sq m of usable floor space — enough for two double bedrooms and a family bathroom in a London Victorian terrace.

    Do I need a party wall agreement for an L-shaped dormer?

    Yes. Because the rear outrigger shares party walls with neighbours, an L-shaped dormer almost always triggers the Party Wall Act 1996. Party Wall Notices must be served before construction begins.

    Get a Free Quote for Your L-Shaped Dormer Loft Conversion

    Crown Architecture specialises in L-shaped dormer loft conversions across London. From initial feasibility check and architectural drawings to building regulations approval and contractor introduction, we handle everything.

    Explore: Loft Conversions | Planning Applications | Structural Engineering | Hackney | Islington | Waltham Forest

  • Building Regulations Part L (Energy Efficiency): What It Means for Your Extension

    If you’re planning a house extension or loft conversion, you’ve probably heard about Building Regulations Part L. It’s one of the most technically complex parts of the building regulations, but it directly affects how warm, energy-efficient, and cost-effective your new space will be to run.

    At Crown Architecture, we incorporate Part L compliance into every project from day one. This guide explains exactly what Part L is, how it applies to extensions and loft conversions in 2025, and what your architect needs to do to ensure your project passes.

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    Interested in a loft conversion or extension? We offer free initial consultations.

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    What Is Building Regulations Part L?

    Building Regulations Part L — officially titled Conservation of Fuel and Power — sets out the minimum standards for the thermal performance and energy efficiency of new buildings and extensions in England and Wales. It was significantly upgraded in June 2022 as part of the transition towards the Future Homes Standard, with targets approximately 30% tougher than previous requirements.

    Part L applies to:

    • New builds
    • House extensions
    • Loft conversions
    • Garage conversions
    • Changes of use (e.g. commercial to residential)
    • Replacement windows, doors, and heating systems in existing homes

    Part L1A vs Part L1B: Which Applies to Your Project?

    Part L is split into two volumes:

    • Part L1A: New dwellings — applies when an entirely new home is being built
    • Part L1B: Existing dwellings — applies when you are extending, altering, or carrying out a change of use on an existing home

    For most homeowners planning extensions or loft conversions, Part L1B is the relevant document.

    U-Values: The Core Requirement of Part L

    The main way Part L is measured and enforced is through U-values — a measure of how much heat passes through a building element per square metre, per degree of temperature difference. The lower the U-value, the better the insulation.

    For extensions and loft conversions in England (2025 requirements under Part L1B):

    Building Element Maximum U-Value (W/m²K)
    Roof 0.15
    Walls 0.18
    Ground floor 0.13
    Windows and doors (new) 1.4 (whole unit)
    Rooflights / skylights 1.4

    These are the notional (target) U-values. In practice, your architect and structural engineer must design the insulation specification to meet or exceed these figures.

    The ‘Worst Case’ Backstop U-Values

    Alongside the target U-values above, Part L also sets absolute maximum (backstop) U-values that must never be exceeded regardless of the overall energy performance of the dwelling. These are:

    • Roof: 0.20 W/m²K
    • Walls: 0.30 W/m²K
    • Ground floor: 0.25 W/m²K
    • Windows/doors: 1.6 W/m²K (whole unit)

    How Part L Affects Extension Design

    Wall Construction

    Achieving a U-value of 0.18 W/m²K in an extension wall typically requires one of the following approaches:

    • Cavity wall with full-fill insulation: A standard brick-and-block cavity wall with 100mm+ of cavity filled with mineral wool or PIR board achieves around 0.18–0.22 W/m²K.
    • Brick with external wall insulation (EWI): Rigid insulation boards fixed to the outside of a solid masonry wall, then rendered — effective and increasingly common.
    • Timber frame with insulation: A structural timber frame filled with mineral wool or spray foam — common in modern extensions and garden rooms.

    Roof Insulation

    For a flat-roofed extension, meeting a U-value of 0.15 W/m²K requires approximately 120–150mm of PIR insulation board (e.g. Kingspan or Recticel). For pitched roofs, 150mm between and below the rafters using PIR boards is typically required.

    Floor Insulation

    Concrete slab floors in extensions need rigid PIR insulation below the slab and around the perimeter. Typically 100–150mm is required to meet the 0.13 W/m²K target.

    Windows and Glazing

    All new windows in extensions must achieve a U-value of 1.4 W/m²K or better. Modern double-glazed units with argon fill and low-e coatings typically achieve 1.2–1.4 W/m²K. Triple glazing (0.6–0.8 W/m²K) exceeds the requirement and is worth considering in north-facing extensions.

    The SAP Assessment and Part L Compliance for Extensions

    For extensions above a certain size, your project may require a SAP (Standard Assessment Procedure) calculation — an energy modelling assessment of the whole dwelling including the new extension.

    Under Part L1B, a SAP assessment is required when:

    • The extension increases the total floor area by more than 25%
    • The extension has a floor area greater than 100 sq m
    • OR if the extension is thermally connected to the existing heated space

    The SAP calculation models how the extension affects the overall energy use of the property. If the extension is worse than the existing house’s average performance, compensatory improvements elsewhere in the dwelling may be required.

    Thermal Bridging and Psi Values

    One area where many extensions fail Part L is thermal bridging — the points where insulation is interrupted by structural elements (junctions of walls and floors, window reveals, lintel positions). Heat escapes through these junctions far faster than through the insulated areas.

    Part L requires architects to account for thermal bridges using Psi values (linear thermal transmittance). Using accredited construction details (ACDs) from the NHBC or BRE minimises bridging and makes Part L compliance easier to demonstrate.

    Part L and Glazing Limits

    One practical constraint of Part L1B is a limit on the total area of glazing in an extension. As a rule of thumb, new windows and doors in an extension should not exceed 25% of the new floor area, unless the overall calculated energy performance can be shown to still meet targets.

    This affects open-plan kitchen extensions with large roof lanterns, bifold doors, and full-width glazed rear walls. Your architect must carefully model the glazing area to demonstrate Part L compliance — or specify higher-performance glass to compensate.

    Part L and Loft Conversions

    Loft conversions are subject to Part L requirements for the new roof insulation and any new windows. For a Velux loft conversion, the main requirement is to insulate between and below the existing rafters to achieve a U-value of 0.15 W/m²K.

    For a dormer loft conversion, the new dormer walls and flat roof must meet Part L independently. The existing pitched roof slopes remaining must also be insulated as part of the works.

    How Crown Architecture Handles Part L Compliance

    Our architectural drawings include full thermal specifications for every element — wall construction, floor build-up, roof insulation, glazing schedule. Where a SAP assessment is required, we commission it from a qualified energy assessor and incorporate any required compensatory measures at design stage, before construction begins.

    We never leave Part L compliance to chance or to the builder — it’s baked into the design from day one, so you don’t face costly remedial work during or after construction.

    Frequently Asked Questions About Part L

    What is Building Regulations Part L?

    Part L of the Building Regulations sets the minimum standards for thermal performance and energy efficiency in buildings in England and Wales. For house extensions and loft conversions, Part L1B applies and sets maximum U-values for walls, roofs, floors, and windows.

    What U-values are required for a house extension in 2025?

    Under Part L1B (2022 edition): walls must achieve 0.18 W/m²K, roofs 0.15 W/m²K, ground floors 0.13 W/m²K, and windows 1.4 W/m²K.

    Do small extensions need to comply with Part L?

    Yes. All house extensions, regardless of size, must comply with Part L of the Building Regulations. The insulation requirements apply to all new walls, roofs, and floors.

    Does a conservatory need to comply with Part L?

    A conservatory is exempt from Part L if it is thermally separated from the main house, has a roof with more than 75% translucency, and is built at ground level. Extensions that don’t meet these conditions must comply with Part L.

    What is a SAP assessment and when is it needed for an extension?

    A SAP assessment models the overall energy use of a dwelling. For extensions, it is required when the extension adds more than 25% to the existing floor area or exceeds 100 sq m. The SAP must show the dwelling’s overall energy performance meets minimum standards.

    Need Help Ensuring Your Extension Meets Building Regulations?

    Crown Architecture handles full building regulations compliance — including Part L thermal specifications — for every project. We work with approved building control bodies and ensure your drawings are compliant before construction starts.

    Learn more: House Extensions, Loft Conversions, Planning Applications, Camden, Islington.

  • Home Office Extension UK: Cost, Planning & Design Ideas 2025

    The rise of remote and hybrid working has made the home office extension one of the most in-demand home improvements in the UK. Rather than squeezing a desk into a bedroom corner or converting a spare room, a dedicated home office extension gives you a proper, professional workspace that is physically separate from your living areas — improving focus, productivity, and work-life balance.

    At Crown Architecture, we design purpose-built home office extensions for homeowners across London. Whether you want a compact garden studio, a full rear extension with a dedicated office wing, or a loft conversion with a light-filled study, this guide will help you understand your options, costs, and the planning rules that apply in 2025.

    📋 Get a Free Quote

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    Why Build a Home Office Extension?

    Working from home sounds straightforward until you’re on a Zoom call with a toddler in the background, or trying to concentrate in a shared kitchen. A dedicated home office extension solves these problems while also:

    • Adding significant property value — a high-quality home office extension can add 5–15% to your property’s value
    • Avoiding costly office rent — the average London office desk costs £8,000–£15,000 per year
    • Creating a professional client-facing space — ideal for therapists, consultants, tutors, and other client-facing professionals who work from home
    • Potentially qualifying for business tax relief — speak to your accountant about using a dedicated work space for capital allowance purposes

    Types of Home Office Extension

    1. Rear Extension with Office Room

    The most common approach: a single-storey or two-storey rear extension where one room is dedicated as a home office. This connects seamlessly to the house, with access to utilities, a toilet, and kitchen — while the dedicated room gives you the separation you need.

    2. Garden Room / Outbuilding Office

    A standalone structure in the garden — separate from the house, with its own insulation, heating, electrics, and broadband. This provides maximum separation from household noise. Many garden room offices fall within permitted development as outbuildings.

    3. Garage Conversion to Home Office

    If you have an integral or attached garage, converting it into a home office is often the most cost-effective route — no new foundations required, and the shell already exists.

    4. Loft Conversion Study

    A loft conversion is ideal for a home office: quiet, away from main living areas, and often flooded with natural light via Velux or dormer windows.

    5. Side Return Extension as Office

    Many London Victorian terraces have a narrow side return — often used as a covered passage or storage. Converting this into a side extension with a dedicated office can add a useful 10–20 sq m at relatively low cost.

    Home Office Extension Costs UK 2025

    Costs vary significantly depending on the type of extension you choose:

    Type London Cost (2025) National Average
    Garden room / outbuilding office (3m × 4m) £15,000 – £35,000 £10,000 – £25,000
    Garage conversion to office £15,000 – £28,000 £10,000 – £20,000
    Single-storey rear extension with office room £35,000 – £65,000 £25,000 – £50,000
    Loft conversion with study room £30,000 – £60,000 £20,000 – £45,000
    Two-storey rear extension (office + room above) £60,000 – £120,000 £45,000 – £90,000

    Does a Home Office Extension Need Planning Permission?

    Whether you need planning permission depends on the size, location, and type of structure.

    Outbuilding / Garden Room Office

    A standalone garden office is typically permitted development provided:

    • It is a single storey with maximum eaves height of 2.5m and maximum overall height of 4m (2.5m within 2m of a boundary)
    • The footprint covers less than 50% of the garden area
    • It is not forward of the principal elevation
    • It is used ancillary to the main house (i.e. not as self-contained accommodation)

    Rear or Side Extension

    Single-storey rear extensions of up to 4m (detached) or 3m (semi/terraced) are generally permitted development. Extensions larger than this, or in restricted areas, need full planning permission.

    Loft Conversion

    A Velux-style loft conversion is typically permitted development. A dormer may or may not require planning permission depending on size and location — see our loft conversions guide for details.

    Building a Home Office Extension: Key Design Considerations

    Natural Light Is Everything

    The single biggest factor affecting productivity in a home office is natural light. Design your extension to maximise north or east-facing windows (to avoid glare) or add roof lights for overhead daylight. Avoid facing a solid brick wall.

    Broadband and Data Infrastructure

    Before walls are plastered, run Cat6 ethernet cables to your desk position. Wi-Fi is convenient, but a wired connection is essential for video calls and large file uploads. Also consider a separate electricity circuit so your office doesn’t trip breakers in the main house.

    Acoustic Insulation

    If you’re on calls all day, acoustic separation from the rest of the house matters. Specify acoustic insulation in party walls and internal floors. Double-glazed windows also help block external noise.

    Climate Control

    Offices get warm with computer equipment running. Include a wall-mounted AC unit or specify a multi-split heat pump system that provides both heating and cooling. Underfloor heating is a great option in extensions, keeping the floor warm without radiators taking up wall space.

    Ergonomics and Storage

    Work with your architect from the outset to plan desk position, storage, and screen placement relative to window positions. A poorly positioned window can create glare on your monitor all afternoon — easily avoided at design stage.

    Home Office Extension in London

    London homeowners have been particularly quick to embrace home office extensions following the shift to remote working. We work regularly across:

    • Hackney — garden office studios in Victorian terraces
    • Islington — loft conversion studies on Georgian townhouses
    • Camden — rear extension home offices on Edwardian semis
    • Ealing — garage conversions to professional home offices
    • Waltham Forest — outbuilding offices in large rear gardens

    Building Regulations for Home Office Extensions

    All extensions and conversions (including garden offices with electrics) require building regulations approval. This ensures the structure is safe, thermally efficient, and properly wired. Key requirements:

    • Structure: Foundations, wall construction, and roof must meet Part A requirements
    • Thermal insulation: Walls, floor, and roof must meet Part L U-value targets
    • Electrical installation: All electrical work must be notified to building control (Part P)
    • Ventilation: Adequate mechanical or passive ventilation required (Part F)
    • Fire safety: Smoke alarms and fire-resistant escape routes required (Part B)

    Frequently Asked Questions

    How much does a home office extension cost in the UK?

    A garden room home office costs £15,000–£35,000 in London. A garage conversion to office costs £15,000–£28,000. A single-storey rear extension with a dedicated office room costs £35,000–£65,000 in London.

    Do I need planning permission for a home office extension?

    Most home office extensions — including garden rooms, garage conversions, and small rear extensions — fall within permitted development rights and do not need planning permission. Larger extensions, or those in conservation areas, will need a planning application.

    Does a garden office need building regulations approval?

    A garden office under 15 square metres with no sleeping accommodation is exempt from building regulations. Above 15 sq m (or 30 sq m if built to certain standards), building regulations approval is required. If the office has electrical installation, that must be notified to building control regardless of size.

    Can I claim tax back on a home office extension?

    If you are self-employed, you may be able to claim capital allowances on a dedicated home office extension used exclusively for business. Always consult a qualified accountant before proceeding.

    How long does a home office extension take to build?

    A garden room office can be built in 2–4 weeks. A garage conversion takes 4–8 weeks on site. A single-storey rear extension typically takes 8–14 weeks. Total project time including design and approvals is usually 4–7 months.

    Ready to Build Your Home Office Extension?

    Crown Architecture designs functional, inspiring home office extensions that make working from home genuinely enjoyable. From free initial consultation to building regulations sign-off, we manage the whole process for you.

    Explore more: House Extensions, Loft Conversions, Garage Conversions, Hackney, Islington.

  • Glass Roof Extension UK: Costs, Design Ideas & Planning Guide 2025

    A glass roof extension is one of the most dramatic and sought-after home improvements in the UK. Whether it’s a full roof lantern flooding your kitchen with light, a glazed link extension connecting house to garden room, or an orangery with a glass apex — a well-designed glass roof transforms how you live and adds serious value to your home.

    At Crown Architecture, we design glass roof extensions across London and the South East. This guide covers everything you need to know in 2025 — from costs and planning rules to the different styles available and the structural considerations your architect needs to address.

    📋 Get a Free Quote

    Interested in a loft conversion or extension? We offer free initial consultations.

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    What Is a Glass Roof Extension?

    A glass roof extension (or glazed roof extension) is a house extension in which some or all of the roof is made from glass or glazed panels. This creates a bright, airy living space that blurs the boundary between inside and outside.

    Common types include:

    • Roof lantern extension: A flat-roofed extension with a raised, glazed lantern in the centre. The most popular choice for kitchen-diners.
    • Full glazed roof: The entire roof surface is glass — creating a garden room or sunroom effect.
    • Glazed link extension: A glass corridor or connection between two structures — elegant and light-filled.
    • Orangery: A hybrid between a conservatory and an extension — solid walls with a glass apex or central roof lantern.
    • Frameless structural glass extension: A modern, minimal design using structural glass fins and frameless glazing for a near-invisible effect.

    Glass Roof Extension Costs UK 2025

    The cost of a glass roof extension in the UK depends heavily on size, glazing specification, frame material, and London vs. non-London location.

    Type London Cost Range National Average
    Roof lantern on flat-roof extension £35,000 – £65,000 £25,000 – £50,000
    Orangery (with glass apex) £40,000 – £80,000 £30,000 – £65,000
    Full glazed roof extension £50,000 – £100,000+ £40,000 – £85,000
    Frameless structural glass extension £80,000 – £150,000+ £65,000 – £120,000

    Key Cost Factors

    • Glazing specification: Low-emissivity (low-e) triple-glazed units are more expensive but dramatically reduce heat loss and solar gain.
    • Frame material: Aluminium frames are most common; timber frames cost more but suit period properties; frameless/structural glass is premium.
    • Roof lantern size: A 1m × 2m lantern costs around £3,000–£6,000; a 2m × 4m lantern costs £8,000–£18,000.
    • Heating and cooling: Glass roofs require underfloor heating and/or HVAC to prevent overheating in summer.
    • Foundations: If the extension ground is clay-heavy (common in London), deeper or pile foundations add cost.

    Planning Permission for a Glass Roof Extension

    Whether you need planning permission for a glass roof extension depends on its size, location, and the materials used.

    When Permitted Development Applies

    Most single-storey rear glass roof extensions up to 4 metres deep (detached) or 3 metres deep (semi or terraced) fall within permitted development, provided:

    • The extension covers no more than 50% of the garden
    • The maximum height doesn’t exceed 4 metres
    • It is located at the rear of the property
    • No part projects beyond a side elevation

    Under the Neighbour Consultation Scheme, extensions up to 8m (detached) or 6m (semi/terraced) may also be permitted subject to no objections from neighbours.

    When Planning Permission Is Required

    • The property is in a conservation area or Article 4 direction area
    • The extension exceeds permitted development size limits
    • The roof material or design is considered unusual by the local planning authority
    • The property is a listed building (listed building consent also required)

    Structural Considerations for Glass Roof Extensions

    Glass is heavy — heavier than most people realise. A proper glass roof extension requires careful structural engineering to ensure the roof is safely supported. Key considerations include:

    • Steel beams: Most glass roof extensions require steel beams (RSJs or box section) to span the opening and support the glass above. These are typically concealed within the structure.
    • Connections to the existing house: The junction between the new glazed roof and the existing house wall must be properly detailed to prevent leaks and cold bridging.
    • Drainage: Glass roofs collect rainwater — internal gutters and hidden downpipes are usually required to maintain a clean aesthetic.
    • Thermal performance: Meeting Part L building regulations is a significant challenge with extensive glazing. Your architect must model the U-values carefully.

    Overheating: The Most Common Glass Roof Problem (And How to Solve It)

    The number one complaint homeowners have about glass roof extensions is overheating in summer. Here’s how to avoid it:

    • Solar control glass: Self-tinting or solar-control coated glass reduces solar heat gain by up to 70% while maintaining excellent light transmission.
    • External solar shading: Motorised external blinds or pergola slats block sun before it enters the glass — far more effective than internal blinds.
    • Roof vents: Opening roof lights or automated vent sections allow hot air to escape, creating natural convection cooling.
    • Underfloor heating (not radiators): Underfloor heating prevents cold draughts pooling at floor level in winter, which is a common problem with highly glazed spaces.
    • MVHR (Mechanical Ventilation with Heat Recovery): A whole-house MVHR system maintains fresh air and temperature balance year-round.

    Design Ideas for Glass Roof Extensions

    1. The Kitchen-Diner Roof Lantern

    The most popular application: a flat-roofed rear extension with a central roof lantern. The solid perimeter roof keeps noise and heat performance manageable, while the lantern provides a dramatic focal point and pours light onto a dining table below. Pair with bifold or sliding doors across the rear for a seamless connection to the garden.

    2. The Full-Width Glazed Lean-To

    A polycarbonate or glass lean-to across the full rear width of the house — glazed roof, glazed rear wall, solid side walls. Cost-effective and maximises light. Best suited to south-facing rear gardens.

    3. The Frameless Glass Box

    For contemporary homes, a glass box extension with structural glass walls and a minimal aluminium roof frame creates a striking architectural statement. Requires a higher budget but delivers an outstanding result.

    4. The Orangery

    A classic orangery features solid walls with cornicing, pilasters, and a glass apex or central lantern. It bridges the gap between a conservatory and a full extension — offering better thermal performance than a conservatory while retaining a period-appropriate aesthetic. Ideal for Victorian and Edwardian properties in London.

    Glass Roof Extensions in London

    London’s Victorian and Edwardian terraces are perfectly suited to glass roof extensions as a way to open up dark rear ground floors into bright kitchen-dining spaces. We regularly work across:

    • Hackney — glass roof kitchen extensions on Victorian terraces
    • Islington — roof lantern extensions on Georgian townhouses
    • Camden — orangeries on Edwardian semis
    • Ealing — glazed rear extensions on inter-war semis

    Conservation area rules in London require careful glazing specification — large plain panes of glass are sometimes preferred to complex grid patterns. Our architects know what each borough’s planners expect and will design accordingly.

    Frequently Asked Questions

    How much does a glass roof extension cost in the UK?

    A glass roof extension with a roof lantern typically costs £35,000–£65,000 in London and £25,000–£50,000 elsewhere in the UK. Full glazed roof extensions or frameless glass box designs can cost £80,000–£150,000+.

    Do glass roof extensions need planning permission?

    Most single-storey glass roof extensions at the rear of a property fall within permitted development rights and do not need planning permission. Planning permission is required if the property is in a conservation area, is listed, or if the extension exceeds permitted development size limits.

    Do glass roof extensions get too hot in summer?

    Overheating is a risk with poorly specified glass roofs. It can be avoided by using solar-control glass, external shading, opening roof vents, and underfloor heating. A well-designed glass roof extension should be comfortable year-round.

    What is the difference between a conservatory and a glass roof extension?

    A conservatory typically has a glass or polycarbonate roof and thin walls, often falling outside building regulations. A glass roof extension is built to full building regulations standard with solid walls and insulated structure, with glass used only in the roof. It performs better thermally and legally counts as a habitable room.

    What is a roof lantern?

    A roof lantern is a raised glazed structure fitted into a flat roof, typically pyramid or rectangular in shape, that allows natural light to flood into the room below. They range in size from 1m × 1m to 3m × 5m or larger and are available in aluminium or timber frames.

    Get a Free Quote for Your Glass Roof Extension

    Crown Architecture designs beautiful, high-performance glass roof extensions across London. Whether you’re imagining a roof lantern kitchen-diner, a frameless glass box, or a classic orangery, we’ll create a design that maximises light and adds lasting value to your home.

    Explore our house extensions service, read about planning applications, or find your area: Hackney, Islington, Camden.

  • Velux Loft Conversion: Cost, Planning & Complete Guide UK 2025

    A Velux loft conversion — sometimes called a roof light or sky light loft conversion — is the most affordable and least disruptive way to add usable living space to your home. By installing Velux-style roof windows into the existing roof structure without altering its shape, you can create a bright, functional room for far less than a dormer or mansard conversion.

    At Crown Architecture, we’ve helped hundreds of London homeowners transform their unused loft space into beautiful bedrooms, home offices, and playrooms. In this guide, we cover everything you need to know about Velux loft conversions in 2025 — from costs and planning rules to design tips and the step-by-step process.

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    What Is a Velux Loft Conversion?

    A Velux loft conversion involves converting your existing loft into habitable space by fitting roof windows (commonly from the Velux brand) directly into the existing roof slope. Unlike a dormer loft conversion, the roofline itself doesn’t change — making it faster, cheaper, and almost always permitted development.

    The result is a light-filled room that makes the most of natural daylight pouring in from above. Velux windows tilt open fully for ventilation and can be fitted with blackout blinds, so they’re ideal for bedrooms and home offices alike.

    Who Is a Velux Loft Conversion Best For?

    • Homeowners with sufficient existing head height (at least 2.2m at the ridge)
    • Those on a tighter budget who still want extra living space
    • Properties where the roof pitch is between 25° and 70°
    • Period homes in conservation areas where a dormer might be refused
    • Homeowners who want minimal disruption and a shorter build time

    Velux Loft Conversion Cost UK 2025

    A Velux loft conversion is consistently the most cost-effective loft conversion type in the UK. Here’s what you can expect to pay in 2025:

    Specification Cost Range (2025)
    Basic Velux loft conversion (London) £18,000 – £28,000
    Mid-range (with en suite) £28,000 – £40,000
    High specification / premium finishes £40,000 – £55,000
    Rest of UK (outside London) £14,000 – £25,000

    These prices include structural work, insulation, Velux windows, plasterboard, flooring, and a staircase. They do not include furniture, blinds, or high-end bathroom fittings.

    What Affects the Cost of a Velux Loft Conversion?

    Several factors influence the final price:

    • Size of the loft: Larger floor areas naturally cost more to finish.
    • Number and size of Velux windows: Each window costs £500–£2,000 depending on size and specification (standard, centre-pivot, or roof terrace style).
    • Structural work required: If floor joists need strengthening or the chimney breast must be removed, costs rise.
    • Bathroom addition: Adding an en suite adds £5,000–£12,000.
    • London premium: Labour costs in London are typically 20–30% higher than the national average.
    • Staircase design: A straight flight is cheapest; a spiral or bespoke staircase costs more.

    Do You Need Planning Permission for a Velux Loft Conversion?

    In most cases, no planning permission is needed for a Velux loft conversion. Because the roofline remains unchanged, it typically falls within permitted development rights.

    However, you will need planning permission if:

    • Your property is in a conservation area or is a listed building
    • Your home is a flat or maisonette
    • Permitted development rights have been removed by an Article 4 direction in your local authority area
    • You’ve already used up your PD allowance with previous works

    We always recommend applying for a Lawful Development Certificate (LDC) from your local council to confirm your project is permitted development. This protects you at the point of sale and gives peace of mind throughout the build.

    Building Regulations for a Velux Loft Conversion

    Planning permission and building regulations are two different things. Even where planning isn’t needed, all loft conversions require building regulations approval. This covers:

    • Structural integrity — ensuring floor joists are strong enough
    • Fire safety — 30-minute fire-resistant doors, smoke alarms on each floor, and safe escape routes
    • Insulation — meeting current thermal performance standards (Part L)
    • Means of escape — a safe staircase and, above two storeys, an emergency egress window
    • Electrical and plumbing — if an en suite is added

    At Crown Architecture, our building regulations service handles everything from initial drawings to sign-off. You won’t need to chase building control — we do it for you.

    How Long Does a Velux Loft Conversion Take?

    A Velux loft conversion is typically the quickest type of loft conversion to complete. A standard project runs as follows:

    • Architectural drawings and structural calculations: 2–3 weeks
    • Building regulations submission and approval: 5–8 weeks (Full Plans route)
    • Build on site: 4–8 weeks depending on size and specification

    From instructing an architect to completion, most Velux loft conversions take 3–5 months in total.

    Velux Loft Conversion vs Dormer: Which Is Better?

    The choice between a Velux and a dormer conversion comes down to your specific circumstances:

    Factor Velux Conversion Dormer Conversion
    Cost Lower (£18k–£40k) Higher (£35k–£60k+)
    Usable floor area Limited by head height Much greater
    Planning required Rarely (usually PD) Sometimes
    Build time 4–8 weeks on site 8–12 weeks on site
    Natural light Excellent (overhead) Good (vertical)

    If your loft already has sufficient head height and you’re primarily looking for an extra bedroom or home office, a Velux conversion often delivers the best value. If you need maximum usable floor space and vertical head room across the whole floor, a dormer is the better choice.

    Velux Loft Conversion in London: Area-Specific Considerations

    London’s Victorian and Edwardian terraced housing stock is well-suited to Velux loft conversions, with pitched roofs that often already provide adequate head height. However, rules vary by borough.

    • In Hackney, some streets are covered by Article 4 directions that restrict PD rights — always check before proceeding.
    • In Camden, conservation areas are widespread, particularly in Hampstead and Primrose Hill — planning permission is often required.
    • In Islington, permitted development rights still apply to most mid-terrace Victorian properties outside conservation area boundaries.
    • In Waltham Forest, roof light conversions are particularly popular on the area’s large Edwardian semis.

    Step-by-Step: How Crown Architecture Handles Your Velux Loft Conversion

    1. Free initial consultation: We visit your property, assess the loft, and advise on the best approach.
    2. Design and drawings: Our architects produce full architectural drawings and structural calculations.
    3. Planning check: We confirm permitted development status or submit for a Lawful Development Certificate.
    4. Building regulations submission: Full Plans application submitted to building control.
    5. Contractor introduction: We introduce you to our vetted network of loft conversion specialists.
    6. Site supervision: Our team oversees the build to ensure it matches the approved drawings.
    7. Final sign-off: Building control inspector approves the completed conversion.

    Maximising Your Velux Loft Conversion

    Choose the Right Velux Windows

    Velux offers several window types for loft conversions:

    • Centre-pivot (standard): Opens from the middle — ideal for bedrooms and studies.
    • Top-hung: Opens from the top, providing a clearer view and better ventilation — perfect for bathrooms.
    • Cabrio (balcony): Transforms into a mini balcony — brilliant for rooms at the front or back of the house.
    • Electric/solar-powered: Opens and closes via remote control or a rain sensor — ideal for hard-to-reach positions.

    Insulation: Don’t Cut Corners

    Proper insulation is essential for a warm, energy-efficient loft room. Current building regulations require a U-value of 0.18 W/m²K for roof insulation. Using high-performance rigid insulation boards between and below the rafters allows you to meet this target without losing too much head height.

    Lighting and Storage

    Make use of the sloping eaves for built-in storage — these areas are often wasted in a poorly designed conversion. Recessed LED downlights look sleek and don’t reduce head height.

    Frequently Asked Questions About Velux Loft Conversions

    How much does a Velux loft conversion cost in London in 2025?

    A Velux loft conversion in London typically costs between £18,000 and £40,000 in 2025, depending on size, specification, and whether a bathroom is included. Outside London, prices range from £14,000 to £25,000.

    Do I need planning permission for a Velux loft conversion?

    Most Velux loft conversions fall within permitted development rights and do not require full planning permission, as the roofline is not altered. However, you may need permission if your property is in a conservation area, is listed, or if PD rights have been removed by your council.

    What head height do I need for a Velux loft conversion?

    Building regulations require a minimum head height of 2.2m at the ridge of the roof for a habitable room. Ideally, you want at least 2.4m to ensure a comfortable, usable space.

    How long does a Velux loft conversion take?

    On site, a Velux loft conversion typically takes 4–8 weeks to complete. Including design, building regulations approval, and site work, the overall project usually takes 3–5 months from instruction to completion.

    How much does a Velux loft conversion add to house value?

    A Velux loft conversion typically adds 15–20% to the value of a property in London. On a £500,000 home, that could mean an increase of £75,000–£100,000 for an investment of £20,000–£35,000.

    Can a Velux loft conversion be used as a bedroom?

    Yes. A Velux loft conversion can be used as a bedroom, home office, playroom, or bathroom — subject to sufficient head height and compliance with building regulations for fire safety, insulation, and means of escape.

    Get a Free Quote for Your Velux Loft Conversion

    Ready to transform your loft into a beautiful, functional room? Crown Architecture provides expert architectural design, planning, and building regulations services for Velux loft conversions across London. We offer a free initial consultation and transparent, fixed-fee pricing.

    Alternatively, explore our full loft conversions service, learn about building regulations, or find your local area page: Hackney, Islington, Camden, Waltham Forest.

  • Hip-to-Gable Loft Conversion: Cost, Benefits and Planning UK

    Hip-to-Gable Loft Conversions: The Complete UK Guide

    A hip-to-gable loft conversion is one of the most effective ways to maximise space in a semi-detached or detached home with a hipped roof. By converting the sloped hip end into a vertical gable wall, you dramatically increase usable loft floor area.

    What Is a Hip-to-Gable Conversion?

    A hipped roof has sloped sides on all four faces — significantly limiting loft space. A hip-to-gable conversion:

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    1. Rebuilds the sloped hip end as a vertical gable wall
    2. Extends the ridge line to match the new gable
    3. Often adds a rear dormer for additional space and light

    Costs UK 2024

    • Hip-to-gable only (no rear dormer): £35,000 – £55,000
    • Hip-to-gable with rear dormer (most common): £45,000 – £70,000
    • Hip-to-gable with full rear dormer and ensuite: £55,000 – £80,000
    • Double-ended (detached houses): £60,000 – £95,000

    In London, add 20–30%. The complexity of rebuilding the roof structure is the main cost driver compared to a standard dormer.

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    Expert architects and structural engineers. Free consultation.

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    Why Choose Hip-to-Gable?

    More Space

    Can increase usable floor space by 20–40% compared to a dormer alone. On a semi-detached with a significant hip, this can mean the difference between a single bedroom and a bedroom plus dressing room and ensuite.

    Better Natural Light

    The new gable wall accommodates side elevation windows, bringing in natural light that a dormer alone cannot achieve.

    Improved Proportions

    A gable end often looks more proportionate than a hip, giving the house a more substantial traditional appearance.

    Planning Permission

    Semi-Detached Houses

    Hip-to-gable conversions are considered permitted development, provided total additional volume does not exceed 50m³ and standard PD conditions are met. No planning permission required in most cases.

    Conservation Areas

    Permitted development rights for roof alterations are restricted. Planning permission will be required, and the authority may resist changes to the roof form.

    Best Suited To

    • 1930s and 1940s semi-detached houses (very common in suburban London)
    • Detached houses with hipped roofs
    • Properties where existing hip severely limits loft space

    Not possible on terraced houses, which typically already have vertical gable walls.

    Frequently Asked Questions

    How much does a hip-to-gable loft conversion cost in London?

    Hip-to-gable loft conversion costs in London typically range from £50,000 to £80,000 for a conversion including a rear dormer.

    Does a hip-to-gable loft conversion add value?

    Yes. A hip-to-gable with bedroom and ensuite typically adds 15–20% to a property’s value in London.

    Can I do a hip-to-gable without planning permission?

    In most cases yes. Hip-to-gable conversions on semi-detached and detached houses in England generally qualify for permitted development, provided total additional roof space does not exceed 50m³ and the property is not in a conservation area.