Crown Architecture

Category: Building Regulations

  • 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.

    📋 Get a Free Quote

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

    Crown Architecture Quote Request

    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.

  • Building Regulations for Loft Conversions: Complete UK Guide

    Building Regulations for Loft Conversions: What Every UK Homeowner Must Know

    Even if your loft conversion doesn’t need planning permission, it will almost certainly need building regulations approval. Building regulations ensure your conversion is safe, structurally sound, and energy-efficient.

    Key Building Regulations for Loft Conversions

    Structural Requirements (Part A)

    The existing floor structure is typically designed to support furniture and people in a bedroom, not the loads of a habitable loft room. Most conversions require strengthening of ceiling joists. Steel beams are often required to carry loads where internal walls cannot be retained.

    📋 Get a Free Quote

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

    Crown Architecture Quote Request

    Fire Safety (Part B)

    The most critical element. Requirements depend on floor height:

    Up to 4.5m (most two-storey homes): Protected staircase with 30-minute fire-resistant construction. Mains-wired smoke alarms on every floor.

    Above 4.5m (most three-storey homes): 60-minute fire doors throughout the escape route and a fire detection system.

    Insulation Requirements (Part L)

    Conversions must meet modern thermal performance standards:

    • Roof slope insulation: 0.18 W/m²K or better
    • Floor insulation: 0.22 W/m²K or better
    • New windows: 1.4 W/m²K or better

    Staircase Requirements (Part K)

    • Minimum width: 800mm (clear of handrails)
    • Maximum pitch: 42°
    • Minimum headroom: 2m
    • Balustrades: 100mm sphere test

    Sound Insulation (Part E)

    For terraced and semi-detached houses, adequate sound insulation between properties must be demonstrated.

    Building Regulations Handled For You

    We manage the full building regulations process on your behalf.

    Call: 07443804841

    How to Get Building Regulations Approval

    Option 1: Full Plans Application

    Submit detailed drawings and specifications before construction. Plans approved in advance. Cost: £750 – £1,500. This is the safest option.

    Option 2: Building Notice

    Give notice to the council and a building control officer inspects at key stages. No plans required upfront.

    Option 3: Approved Inspector (Private)

    A private approved inspector carries out building control — often faster and more flexible than the council.

    Stage Inspections During Construction

    1. Commencement
    2. Structural elements
    3. Insulation
    4. Fire protection
    5. Drainage and electrics
    6. Final inspection — completion certificate issued

    Frequently Asked Questions

    Do I need building regulations for a loft conversion?

    Yes. Almost all loft conversions require building regulations approval in England and Wales. This covers structural safety, fire escape, insulation, staircases, and electrical work — even if planning permission is not required.

    How long does building regulations approval take?

    A Full Plans application is typically reviewed within 5 weeks. The final completion certificate is issued after the final inspection on site.

    What happens if I don’t get building regulations?

    Without a completion certificate you may have difficulty selling your home. The council can also require you to remedy non-compliant work at your own cost.

  • Party Wall Agreement — Everything You Need to Know

    Terraced houses sharing a party wall in London

    Party Wall Agreement — Everything You Need to Know

    If you are planning an extension, loft conversion, or any works near a shared boundary, you may need to deal with the Party Wall Act. This is one of the most misunderstood areas of construction law for homeowners — and one that, if ignored, can cause significant delays, disputes, and costs. This complete guide from Crown Architecture & Structural Engineering explains everything you need to know about party walls and the Party Wall Act 1996.

    What is a Party Wall?

    A party wall is a wall that straddles the boundary between two properties and is shared by two (or more) owners. Common examples include:

    • The wall between two semi-detached houses
    • The wall between two terraced houses
    • A garden wall built on the boundary between two properties
    • Floors and ceilings between flats in a converted building (referred to as party structures)

    A wall that stands entirely on one side of the boundary and is not shared is not a party wall, even if it is very close to the boundary.

    The Party Wall Act 1996

    The Party Wall etc. Act 1996 provides a framework for preventing and resolving disputes between building owners and their neighbours in relation to party walls, party structures, boundary walls, and excavations near neighbouring buildings. It applies in England and Wales only.

    The Act requires building owners who intend to carry out certain types of work to give formal notice to their neighbours (adjoining owners) before starting. The Act is not about permission — your neighbours cannot veto your works simply because they object. Instead, it provides a mechanism for resolving any disputes about the works before they start, and for protecting neighbours from damage caused by the works.

    When Do You Need a Party Wall Agreement?

    You must serve notice under the Party Wall Act for three categories of works:

    1. Works Directly to a Party Wall or Party Structure (Section 2)

    Works such as cutting into the party wall to insert a beam or flashing, raising the height of the party wall, demolishing and rebuilding the party wall, underpinning the party wall, and inserting a damp-proof course. These are the most commonly triggered provisions for domestic extensions and loft conversions.

    2. New Building at or on the Boundary Line (Section 1)

    If you intend to build a new wall at the line of junction between your property and your neighbour’s, you must serve notice. This applies even if the wall will be built entirely on your own land.

    3. Excavations Near a Neighbouring Building (Section 6)

    If you intend to excavate within 3 metres of a neighbouring building where the excavation will go deeper than the foundations of that building, or within 6 metres where the excavation will be deeper than a 45-degree line drawn down from the bottom of the neighbour’s foundations, you must serve notice. This provision is particularly relevant for basement extensions and new extension foundations close to the boundary.

    How the Party Wall Process Works

    Step 1: Serve Notice

    The building owner (the person carrying out the works) must serve written notice on all adjoining owners. The notice must describe the works and state the proposed start date. The notice periods are:

    • Section 2 works (party wall works): At least 2 months before the intended start date
    • Section 1 works (new wall on boundary): At least 1 month before the intended start date
    • Section 6 works (excavations): At least 1 month before the intended start date

    Step 2: Neighbour Responds (14 days)

    The adjoining owner has 14 days to respond to the notice. They can:

    • Consent in writing — works can proceed, no further party wall process is required (though it is still advisable to carry out a Schedule of Condition)
    • Dissent and agree to a single agreed surveyor — one surveyor acts for both parties
    • Dissent and appoint their own surveyor — each party appoints their own surveyor, who together select a third surveyor if needed
    • Fail to respond within 14 days — this is deemed a dissent, and the process continues as if they had dissented

    Step 3: Appoint a Surveyor

    If the adjoining owner dissents (or is deemed to have dissented), a party wall surveyor is appointed. The surveyor’s role is to act impartially — even the building owner’s surveyor is duty-bound to act impartially under the Act. The surveyor(s) will agree a Party Wall Award.

    Step 4: The Party Wall Award

    The Party Wall Award is a legal document that sets out the works that may be carried out, the conditions under which they may be carried out (hours of work, protection measures, etc.), the right of access for the surveyor to inspect, and who pays the surveyor’s fees (typically the building owner). It may also include a Schedule of Condition (see below).

    Once the Award is agreed, the building owner can carry out the works described. The neighbour cannot stop the works, but if damage is caused, the Award provides a mechanism for resolution.

    Schedule of Condition

    A Schedule of Condition is a photographic and written record of the condition of the neighbouring property — particularly the walls, ceilings, and floors adjacent to the works — before the works start. It is prepared by the party wall surveyor and agreed by both parties. If the neighbour later claims that the works caused damage, the Schedule of Condition provides an objective baseline against which to assess any claims. A Schedule of Condition is highly recommended for all party wall works, even where the neighbour has consented.

    Party Wall Costs

    Scenario Typical Cost
    Agreed (single) surveyor £700 – £1,200
    Building owner’s surveyor (separate surveyors) £800 – £1,500
    Adjoining owner’s surveyor (paid by building owner) £600 – £1,500
    Total cost — agreed surveyor £700 – £1,200
    Total cost — separate surveyors £1,400 – £3,000+

    The building owner pays all reasonable party wall surveyor fees — both their own and the adjoining owner’s. The neighbour is entitled to appoint a surveyor and have their costs paid by you, regardless of whether they consent or dissent. Budget accordingly.

    What Happens If a Neighbour Objects?

    It is important to understand that the Party Wall Act does not give neighbours a veto over your works. If your neighbour objects (dissents), this triggers the formal party wall process — a surveyor is appointed and a Party Wall Award is agreed. The Award allows the works to proceed. Your neighbour cannot legally stop you from carrying out works to which the Act applies, as long as you have followed the correct process.

    However, if your neighbour refuses to engage in the party wall process entirely, you may need to make a court application, which is time-consuming and expensive. In practice, the vast majority of party wall disputes are resolved through the surveyor process without going to court.

    Party Walls and Building Regulations

    The Party Wall Act is entirely separate from planning permission and building regulations. You must deal with all three separately. Crown Architecture manages the planning and building regulations process for all our projects, and we can refer you to qualified party wall surveyors from our professional network. For more on planning and building regulations, see our guides on house extensions and loft conversions.

    Get a Free Quote from Crown Architecture

    Speak to our expert architects today

    Frequently Asked Questions

    Do I need a party wall agreement for a loft conversion?

    A loft conversion may trigger the Party Wall Act if the works involve cutting into the party wall (for example, to insert steel beams), raising the party wall, or if structural works affect the shared wall in any way. Most loft conversions on semi-detached or terraced houses will involve some works to the party wall and will therefore require notice to be served. Crown Architecture will identify whether your loft conversion requires party wall notice at the design stage.

    Can my neighbour stop my extension using the Party Wall Act?

    No. The Party Wall Act does not give your neighbour a veto over your works. If your neighbour dissents, the formal party wall process is triggered — a surveyor is appointed and a Party Wall Award is issued that allows the works to proceed. Your neighbour may be able to slow the process down if they are obstructive, but they cannot ultimately prevent you from carrying out works that comply with the Act.

    Who pays for the party wall surveyor?

    The building owner (the person carrying out the works) pays all reasonable party wall surveyor fees — including the adjoining owner’s surveyor’s fees. This applies whether one agreed surveyor is appointed or whether each party appoints their own surveyor. The only exception is where the works are being carried out at the adjoining owner’s request or for their benefit, in which case costs may be shared.

    What is the difference between a party wall notice and a party wall agreement?

    A party wall notice is the formal written notice served on your neighbour before the works start. A party wall agreement (more correctly called a Party Wall Award) is the document produced by the party wall surveyor(s) that sets out the terms under which the works may be carried out. A Party Wall Award is only required if the neighbour dissents to the notice. If the neighbour consents in writing, no formal Award is needed (though a Schedule of Condition is still advisable).

    Does the Party Wall Act apply to rear extensions?

    A rear extension may trigger the Party Wall Act in two ways. If the extension foundations are within 3 metres of the neighbouring foundations (very common on terraced houses with a shared rear boundary), a Section 6 excavation notice must be served. If the extension is being built against or close to the party wall, or if any works are to be carried out on the party wall itself, a Section 2 notice must be served. Crown Architecture will identify which notices are required for your specific project.

  • Building Regulations vs Planning Permission — What’s the Difference

    Architect reviewing building regulations documents

    Building Regulations vs Planning Permission — What is the Difference?

    Homeowners planning an extension, loft conversion, or other building project frequently confuse planning permission and building regulations. They are two entirely separate approval systems, administered by different parts of your local council, covering different aspects of your project. Understanding the difference is essential before you start any project. This guide from Crown Architecture & Structural Engineering explains both systems clearly.

    Get a Free Quote from Crown Architecture

    Tell us about your project and we’ll respond within 24 hours.

    📋 Get a Free Quote

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

    Crown Architecture Quote Request

    The Key Difference

    In simple terms:

    • Planning permission controls whether you are allowed to build something — it is about the principle of the development, its size, appearance, and impact on the surrounding area.
    • Building regulations control how you build it — they are technical standards covering structural integrity, fire safety, thermal performance, drainage, and the health and safety of the people who will use the building.

    You may need one, the other, or both, depending on what you are doing. Some projects require planning permission but not building regulations (rare). Most require building regulations but not planning permission. Major works usually require both.

    What Does Planning Permission Cover?

    Planning permission considers the visual impact and amenity of proposed development. When assessing an application, a planning officer will consider:

    • The size, scale, and massing of the proposed development
    • Its appearance and materials, and whether it is appropriate in the context of the street and neighbourhood
    • The impact on the privacy and amenity of neighbouring properties (overlooking, overshadowing, loss of outlook)
    • Impact on protected trees, ecology, or heritage assets
    • Car parking, access, and highway safety
    • Compliance with the National Planning Policy Framework, Local Plan, and any neighbourhood plan policies

    Planning permission is administered by the local planning authority (LPA), which is typically your district or borough council. It is a democratic process — applications are publicly advertised, neighbours can comment, and decisions can be made by an elected planning committee.

    What Do Building Regulations Cover?

    Building regulations are technical minimum standards that apply to most building work in England and Wales. They are set out in the Building Regulations 2010 and the Approved Documents that support them. The key Parts are:

    PartWhat It Covers
    Part AStructure — loads, foundations, walls, floors, roofs
    Part BFire Safety — means of escape, fire spread, access for fire services
    Part CResistance to Contaminants and Moisture — damp-proofing, ground contamination
    Part EResistance to Sound — sound insulation between dwellings
    Part FVentilation — natural and mechanical ventilation
    Part LConservation of Fuel and Power — insulation, energy efficiency, U-values
    Part MAccess to and Use of Buildings — accessibility requirements
    Part PElectrical Safety — notifiable electrical work

    Building regulations are enforced by building control, which is either the local authority building control service or an approved inspector (a private sector body). Building control is a technical process, not a democratic one — there are no public consultations or committees.

    When Do You Need Each?

    Type of WorkPlanning Permission?Building Regs?
    Rear extension (within PD limits)No (permitted development)Yes
    Rear extension (exceeds PD limits)YesYes
    Loft conversionOften no (PD)Yes
    Internal structural alterationNoYes
    Change of use (e.g. office to flat)Usually yes (or prior approval)Yes
    New fence (under 2m)NoNo
    Garage conversionUsually no (PD)Yes

    Full Plans vs Building Notice

    There are two main ways to obtain building regulations approval:

    Full Plans Application: You submit detailed drawings and specifications to building control before work starts. Building control reviews and approves the plans before construction begins. This is the recommended approach for most projects, especially complex ones, because it identifies any compliance issues before work starts rather than after.

    Building Notice: You notify building control that work is starting but do not submit detailed drawings for prior approval. Building control inspects the work as it progresses. This is quicker to start but carries the risk that non-compliant work may need to be undone and rebuilt.

    Crown Architecture prepares full plans applications as standard, ensuring your project is properly documented and building control approval is obtained before work begins.

    Inspections and the Completion Certificate

    Throughout the construction process, the building control officer will carry out inspections at key stages — typically: commencement, foundations, damp-proof course, structural steels, insulation, drainage, and final completion. It is the contractor’s responsibility to notify building control at each stage.

    Once all work is satisfactorily completed, building control issues a Completion Certificate. This is a crucial document — it confirms that the building work has been inspected and complies with the building regulations. Without it, you may encounter difficulties when selling the property.

    Consequences of Non-Compliance

    Carrying out building work that requires building regulations approval without obtaining it is a criminal offence. The local authority can issue an enforcement notice requiring you to open up or demolish non-compliant work. When you come to sell your property, a solicitor will ask for evidence of building regulations compliance for any notifiable work. If you cannot provide it, you may need to obtain indemnity insurance or retrospective regularisation, which is costly and uncertain.

    Crown Architecture manages the building regulations process on every project we undertake, ensuring you receive your completion certificate. For more information on the end-to-end process, see our guides on loft conversions and house extensions in London.

    Get a Free Quote from Crown Architecture

    Speak to our expert architects today

    Frequently Asked Questions

    Can I get building regulations approval without planning permission?

    Yes. Many projects require building regulations approval but not planning permission — for example, a rear extension carried out under permitted development rights still needs building regulations approval. Building control and planning are entirely separate systems. Building control will not check whether you have obtained planning permission, and the planning authority will not check whether you have building regulations approval. It is your responsibility to ensure you have all the necessary approvals for your project.

    What happens if I sell my house without a building regulations completion certificate?

    If you cannot provide a completion certificate for notifiable building works, your solicitor will flag this as a potential issue in the conveyancing process. The buyer’s solicitor may require you to obtain indemnity insurance to cover the risk of enforcement action. Alternatively, you can apply for a regularisation certificate from the local authority, which involves an inspection of the completed work. Neither option is ideal — the best approach is to ensure all work is properly signed off at the time of construction.

    Do I need building regulations for a kitchen renovation?

    A like-for-like kitchen renovation (replacing units and appliances in the same positions) does not typically require building regulations approval. However, if you are moving a gas supply, adding new electrical circuits, or relocating drainage, individual elements may be notifiable. Gas work must be carried out by a Gas Safe registered engineer, and certain electrical work must be carried out by or notified to building control by a Part P registered electrician.

    How much do building regulations applications cost?

    Building regulations fees are set by each local authority or approved inspector and vary depending on the type and scale of work. For a typical single-storey rear extension, the full plans fee is typically £800–£1,200. For a loft conversion, expect to pay £1,000–£1,500. Fees for larger or more complex projects are higher. Crown Architecture includes the building regulations drawings in our fee — you pay the application fee directly to building control.

    What is an approved inspector and should I use one?

    An approved inspector is a private sector body (or individual) registered with the Construction Industry Council (CIC) to carry out building control work. They provide an alternative to local authority building control. Approved inspectors can sometimes offer a more responsive service and are often preferred for commercial and larger residential projects. For straightforward domestic projects, local authority building control is perfectly adequate and is the most commonly used route.