Call or Text: 07443804841

House Extension Islington | Rear, Side & Wraparound Extensions | Crown Architecture

RIBA-aligned practice | 300+ extensions completed | 97% planning approval rate | 5-star Google reviews | Serving N1, N4, N5, N7, N16, N19, EC1

Crown Architecture is a specialist house extension practice with extensive experience across Islington and the the London Borough of Islington area. Whether you are planning a rear kitchen extension, a side return extension, a wraparound, or a two-storey addition, we design and deliver extensions that transform how you live in your home — and how much it is worth.

We manage the entire process from initial concept through to planning permission, building regulations, and contractor support. One fixed fee, one point of contact, from start to finish.

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Types of House Extension We Design in Islington

1. Rear Extension

The most common type of house extension in Islington. A rear extension extends the footprint of the house into the rear garden, typically creating a larger kitchen, dining room, or open-plan living space. Single-storey rear extensions of up to 4 m (for a semi-detached or terraced house) or 8 m (for a detached house) may be built under permitted development, subject to a prior approval notification to the London Borough of Islington.

The typical build cost for a single-storey rear extension in Islington is £1,500–£2,200 per sq m, depending on specification. A 20 sq m rear extension therefore costs in the region of £30,000–£44,000 for the construction works.

2. Side Return Extension

The Georgian, Victorian, and Edwardian terraced properties — many in conservation areas — that define across Islington frequently have an underused side alley — the side return — running alongside the kitchen. Infilling this space with a glazed side return extension creates a much wider, brighter kitchen that opens fully onto the garden. Side return extensions are transformative in the typical Victorian and Edwardian terrace found across Islington.

Side return extensions are usually permitted development, though the proximity to the party wall often means a Party Wall Agreement with the neighbour is required. We advise on this as part of our service.

3. Wraparound Extension

A wraparound extension combines a rear extension with a side return infill to create an L-shaped addition at ground floor level. This maximises the available footprint and is particularly popular with larger families who want an expansive open-plan kitchen, dining, and living space.

Wraparound extensions typically require planning permission. Our architects have extensive experience preparing applications that demonstrate compliance with the London Borough of Islington’s residential extension design guidelines.

4. Two-Storey Extension

Where a single storey is not enough, a two-storey extension adds floor space at both ground and first floor level. This is an efficient way to add a bedroom and bathroom above a new kitchen or living room. Two-storey extensions always require planning permission.

5. Loft Conversion Combined with Extension

Many of our Islington projects combine a ground-floor extension with a loft conversion, maximising the home’s total floor area in a single project. We manage both elements under a single fixed fee, with coordinated planning and building regulations submissions.

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Planning Permission for House Extensions in Islington

Islington is one of London’s most densely built inner boroughs, with a housing stock dominated by Georgian and Victorian terraces. The London Borough of Islington has 13 conservation areas covering large parts of the borough, including the Angel, Barnsbury, Canonbury, De Beauvoir, Highbury, and Thornhill Square. In conservation areas, permitted development rights are significantly restricted: rear extensions visible from a public thoroughfare, side extensions, and works that alter the character of the property all require planning permission. Islington’s supplementary planning documents on extensions in conservation areas set demanding design standards. Our architects specialise in designing extensions that meet these standards and we have an excellent track record of securing planning consent across Islington’s conservation areas.

Where planning permission is required, our drawings are prepared to the standard required by the London Borough of Islington’s planning validation checklist, and we handle the submission and management of the application. Our 97% first-time approval rate reflects our understanding of how to design extensions that meet the London Borough of Islington’s published design criteria.

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Party Wall Agreements for Islington Extensions

If your extension is being built on or near a boundary with a neighbouring property, or involves excavation within 3–6 m of a neighbour’s foundations, the Party Wall etc. Act 1996 requires you to serve notice on your neighbours. We advise on which walls and excavations are affected and can recommend Party Wall surveyors who work regularly across Islington.

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Building Regulations for House Extensions

All extensions require building regulations approval. The key areas include:

• Structure: Foundations, walls, beams, and lintels must be designed to carry the loads imposed. Our in-house structural engineer produces full calculations.
• Insulation: The new walls, roof, and floor must meet current Part L thermal performance standards. We specify insulation to achieve U-values that are building regulations compliant and will reduce your heating bills.
• Fire safety: Where the extension changes the layout of escape routes, Part B fire safety requirements apply.
• Drainage: Any new drainage must connect to the existing system in a compliant way. We coordinate drainage design as part of our drawings.
• Glazing: New windows and doors must meet minimum energy performance requirements and satisfy safety glazing rules where appropriate.

Our Process for House Extensions in Islington

1. Free initial consultation: We discuss your brief, visit the property, and assess feasibility — at no charge.
2. Measured survey: We produce full existing drawings of the property, inside and out.
3. Concept design: We develop design options and 3D visualisations for your review.
4. Planning application: Where required, we prepare and submit the planning application to the London Borough of Islington.
5. Building regulations: We produce detailed working drawings and structural calculations for building regulations.
6. Contractor support: We help you select a reliable local builder and review their tender prices.

Why Choose Crown Architecture for Your Islington Extension?

• Fixed fee of £700: Our design fee is fixed for standard extension projects. No hourly rates, no surprises.
• 97% planning approval rate: We understand what the London Borough of Islington expects and prepare drawings accordingly.
• RIBA-aligned: We follow RIBA professional standards and hold full professional indemnity insurance.
• In-house structural engineering: Structural calculations included — no additional structural engineer required.
• Local knowledge: Deep familiarity with the London Borough of Islington’s planning policies and the character of housing across Islington.
• 5-star client reviews: Consistently rated excellent for design quality, planning success, and client service.

How Much Does a House Extension Cost in Islington?

Build costs for extensions in Islington depend on size, specification, and current market conditions. General guidance:

• Single-storey rear extension (20 sq m): £30,000–£45,000
• Side return extension (15 sq m): £22,000–£35,000
• Wraparound extension (30 sq m): £45,000–£70,000
• Two-storey extension (40 sq m total): £55,000–£85,000

These are construction costs only. Our fixed architectural fee of £700 covers all design, planning, and building regulations drawings.

Areas We Serve Within Islington

Our architects work across the full extent of the London Borough of Islington, covering all postcodes in N1, N4, N5, N7, N16, N19, EC1. We are familiar with the planning policies and design character of each neighbourhood, from conservation area streets to more modern suburban developments. Whatever the property type or location within Islington, we have the local knowledge to design an extension that will secure planning consent and add lasting value.

We also work in all neighbouring boroughs and across Greater London. If you are unsure whether we cover your area, please call or email and we will be happy to confirm.

Get a Free Quote for Your Islington House Extension

Contact our architects today to discuss your Islington extension project. Free initial consultations, no obligation. Call or text 07443804841, email info@crownarchitecture.co.uk, or use the form below.

Sustainable House Extensions in Islington

Modern building regulations set demanding energy performance standards for new extensions, but a well-designed extension can go further. We specify materials and details that minimise heat loss, improve air quality, and reduce running costs:

• Insulation: We design wall, floor, and roof insulation to achieve U-values that meet or exceed the minimum required by Part L. Typical specifications use mineral wool or rigid PIR board to achieve wall U-values of 0.18 W/m²K or better.
• Glazing: Large glazed areas to the rear and south elevations can be a significant source of heat gain in summer and heat loss in winter. We specify glazing with appropriate solar control and thermal performance, and design roof overhangs or louvres where needed to manage solar gain.
• Airtightness: We design junction details to minimise air infiltration and specify airtight membranes where appropriate. Good airtightness reduces energy bills and improves comfort.
• Natural ventilation: We design window positions to promote natural cross-ventilation, reducing the need for mechanical cooling in summer.

Design Quality in Islington House Extensions

The best extensions feel like they were always part of the house, not an afterthought. We achieve this through careful attention to proportions, materials, and the relationship between the new and existing structure. In Islington, this typically means:

• Matching or complementing brick courses, bond, and colour to the existing property
• Designing roof forms that sit comfortably with the existing building rather than conflicting with it
• Using rooflights and glazed elements to bring light deep into the plan
• Considering the connection to the garden — bi-fold or sliding doors, level thresholds, and the relationship between interior and exterior levels
• Designing kitchen layouts, structural spans, and column positions in coordination with the architectural design, so the structural solution supports rather than compromises the layout

Frequently Asked Questions — House Extensions in Islington

Do I need planning permission for a rear extension in Islington?

Not always. Single-storey rear extensions up to 4 m (semi/terraced) or 8 m (detached) may be built under permitted development, subject to prior approval. We check each property and confirm before proceeding. Properties in conservation areas or with an Article 4 Direction have restricted permitted development rights.

How long does a house extension take in Islington?

A single-storey extension typically takes 8–14 weeks on site. Add 4–8 weeks if a planning application is required. We agree a realistic programme before works begin.

Will a house extension add value in Islington?

Extensions consistently add value in Islington. A well-designed rear or side return extension frequently adds more than the build cost to the property’s sale price, particularly in higher-value streets.

What is Crown Architecture’s fee for a house extension?

Our fixed architectural fee is £700 for standard house extension projects, covering measured survey, concept design, planning drawings, building regulations drawings, and structural calculations.

Do I need a Party Wall Agreement for my Islington extension?

If the extension is on or near a boundary, or involves excavation within 3–6 m of a neighbouring building’s foundation, the Party Wall etc. Act 1996 will apply. We advise on this as part of our initial assessment.

Can I combine a house extension with a loft conversion in Islington?

Yes — this is one of the most efficient ways to maximise your home’s floor area. We manage both elements under a single fixed fee with coordinated planning and building regulations submissions. Many clients find the combined cost is significantly less than commissioning two separate projects.

What materials are typically used for house extensions in Islington?

The most common approach is to match the existing brick in colour, texture, and bond, so the extension reads as part of the original building. Where a contemporary contrast is preferred, we work with render, timber cladding, or zinc standing seam roofing. We advise on the planning implications of different material choices for each specific property and location.

How do I find a good builder for my Islington extension?

We recommend getting three quotes from local builders who have experience of the type of work you are planning. We can provide a shortlist of builders who have worked on our projects in Islington and neighbouring boroughs. We also review the quotations you receive to ensure they cover the full scope of work described in our drawings, and advise on the construction contract to use.

Do I need an architect for a house extension in Islington?

You are not legally required to use an architect for a house extension. However, using a qualified architect significantly increases the likelihood of securing planning consent, ensures the building regulations drawings meet the required standard, and typically results in a better-designed, more valuable space. Our fixed fee of £700 makes professional architectural services accessible for any homeowner in Islington.