House Extensions Islington
Single storey rear and double storey extensions in Islington, planning, structure and build under one contract.
- Rated 4.9 from 31 reviews on MyBuilder
- Single-storey rear extension from £40,000
- Free site survey, itemised quote
GS Renovation builds extensions across Islington, from Highbury's Victorian terraces to converted warehouses near Old Street and Clerkenwell. We handle foundations, steelwork, roofing and fit-out, and we tell you straight whether your project is permitted development or needs planning permission from Islington Council.
In Islington, a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m² (indicative London ranges, Architecture for London, Resi, MyBuilder and Checkatrade, 2026). GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Islington: the structural engineer we appoint designs the structure, we build it, and building control signs it off.
Price guide
| Work | Indicative London range |
|---|---|
| Single-storey rear extension | from £40,000 |
| Rear extension, per m² | £2,000 to £2,800 |
| Side return, per m² | £2,400 to £3,200 |
| Wraparound, per m² | £2,400 to £3,200 |
| Double storey, per m² | £1,800 to £2,600 |
| Basement extension | see the basement page |
Indicative London ranges (Architecture for London, Resi, MyBuilder and Checkatrade, 2026), not a quotation. Prices checked September 2026. Full breakdown: Extension Costs & Planning.
Quick estimate for Islington
Islington range: choose above
Rear and side-return extensions in Islington
The side return on an Islington Victorian terrace is often dead space, a narrow strip beside the rear closet wing that lets little light in. Filling it, and extending across the back, turns a cramped kitchen into a wide, open living space. We dig and pour foundations to suit the ground, install the steel beams that carry the existing rear wall, and tie the new roof and glazing into the original house neatly.
Because these terraces sit shoulder to shoulder, a rear extension almost always involves the party wall, so you serve party wall notice on the neighbours before groundworks begin, using the drawings we supply. Many single-storey rear extensions fall under permitted development, but conservation-area status across much of Islington, or a listed building, can restrict those rights for side or larger extensions and require a planning application. We assess your specific address early, so you know which route applies before any design is finalised.
Housing in Islington
The stock in Islington runs to roughly 112,190 dwellings, 85% of them flats and 15% houses, built 43% before 1919, 4% between 1919 and 1939 and 50% after 1945. A flat in Islington has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent, which matters here because most homes are flats.
What Islington's design guidelines allow at the back of a house
Islington has design guidelines for each conservation area, and two of them, for Angel and for Highbury Fields, set the same limit. Both say full width rear extensions higher than one storey, or half width rear extensions higher than two storeys, will not normally be permitted. That points to the shapes worth drawing: a full width single storey across the back, or a narrower addition that stops at two storeys. The Highbury Fields guidelines add that, apart from properties listed in Schedule 5.6, planning permission for side extensions will not be granted. On those streets a side return infill is checked against that schedule before anyone designs one.
Flats need a different route altogether. Islington Council says you need to apply for full planning permission to add an extension or conservatory to a flat. With 85% of Islington homes being flats, a ground floor flat with a garden starts from an application rather than a permitted development check. The freeholder's consent runs alongside it. Behind a terrace the new floor may also cross a shared drain, and Islington says a building notice cannot be used when building over existing sewers and drains. A drain survey early on tells you which building control route the extension will need.
Double storey and wrap-around Islington projects
On the larger plots around Highbury Fields and Canonbury, a double-storey or wrap-around extension can add a proper kitchen-diner below and a bedroom or bathroom above. These schemes carry more load, so the steel design and foundations matter even more, and they almost always need a full planning application to Islington Council rather than falling under permitted development. We coordinate the drawings from your architect or designer and the calculations from the engineer we appoint, then build the whole scheme under one contract.
Warehouse and Clerkenwell conversions play by different rules. Many are leasehold flats where structural change needs the freeholder's licence to alter and coordination with the managing agent, and building-management rules on sound insulation between flats still apply. We work within those constraints, keeping neighbours informed and the block's conditions met. Whether your extension is a house at the back or a reconfiguration inside a converted building, we build to Building Regulations and get it inspected.
Kitchen extensions in Islington
85% of homes in Islington are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Islington Council and the freeholder's consent. Most kitchen extensions here are on the 15% of homes that are houses. The fit-out is priced on its own page, kitchen renovation in Islington; the build figures are in the table above.
- Full fit-out, finishing and making good
- Building control inspections at foundation, damp course and steel stages
- Levels, drainage and landscaping made good around the new build
VOA Council Tax stock of properties, March 2025, for all 23 statistical areas in Islington. Counts rounded by the VOA.
Why Choose GS Renovation in Islington
Islington homeowners choose GS Renovation because we deliver the whole extension, from coordinating the drawings and the engineer to groundworks, steel, roof and finish, with one team accountable throughout. After our founder's 30+ years on the tools, we know the borough's terraces, conservation areas and party wall demands. We guide you honestly on permitted development versus planning, and we build to last.
- Programme planned around party wall notice periods before excavation near a neighbour
- Aftercare and snagging support once the job is finished
- Building control inspected at foundation, damp course and steel stages
Reviewed jobs near Islington
1 MyBuilder review from Islington, with each customer's own job title:
- Kitchen refit in ex-local authority maisonette, Islington, 8 Jul 2022 (5 out of 5)
Read all 31 on our reviews page.
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
Saaid is the best craftsman I have worked with. He knows what he is doing from the very beginning. He has a great knowledge of construction…
FAQ
Frequently Asked Questions about House Extensions Islington
What is the going rate for house extensions around Islington?
Three Islington builders will give three different numbers for house extensions in Islington, usually because they have scoped three different jobs within £2,000 to £2,800 per m² for a rear extension (indicative). GS Renovation prices the N1 property after a survey and sets out labour, materials, approvals and making good in the order they happen: the steel into the house is designed before the rear wall comes down.
Does my Islington rear extension need planning permission or is it permitted development?
Many single-storey rear extensions are permitted development, and in a conservation area that right survives within its limits unless an Article 4 direction removes it, but side extensions and two-storey rear extensions lose permitted development there. Large parts of Islington are conservation areas, and a listed house needs listed building consent whatever the planning route. Double-storey and wrap-around schemes usually need a planning application to Islington Council. We check your exact address before drawings start so there are no surprises.
Does an Islington side-return infill involve the neighbour's side of the wall?
Usually. Islington terraces sit shoulder to shoulder, so the new wall is at or near the boundary and the foundations are dug close to next door. Excavating below their footings within 3 metres of the house triggers a month's notice under the Party Wall Act. Next door may consent; if they dissent, surveyors make an award.
Can I extend a flat in a converted Islington house?
Possibly, but permitted development does not help, since it covers houses only. A flat extension needs planning permission from Islington Council, the freeholder's consent, and Building Regulations approval. Since 85% of Islington homes are flats on VOA figures, this is the more common starting point here.
How is light brought into an Islington side-return extension?
Mostly from above, because the boundary wall blocks side light. Rooflights along the infill or a glazed roof bring daylight deep into the middle room. Under Part L the glass counts against the insulation standard, so a large glazed area may mean better insulation elsewhere. In a conservation area, planners may also consider how the roof looks.
What does a double storey extension in Islington need that a single storey does not?
Heavier steel, deeper foundations and almost always a full planning application to Islington Council. The upper floor adds load to the new walls and to the steel that replaces the rear wall, so the engineer designs both levels together. Building control inspects at each stage, from foundations to completion.
Does Islington need notice before a tree is cut back for an extension?
In a conservation area, yes. You must give the Council six weeks notice in writing before any work is carried out to prune or fell a tree. Extensions often need a tree cut back to clear the footings, the scaffold or the new roof line, so that notice goes in when the drawings are settled, not the week the digger arrives. Roots near the new footings are also shown to the structural engineer we appoint, because they affect the foundation depth.
Is Islington's householder pre-application advice worth using before an extension application?
Where the design pushes against a guideline, it usually is. Islington offers householder pre-application written advice, a version with a site visit, and follow-up advice after that. A rear extension on a conservation area street, or one close to the one storey and two storey limits in the Angel and Highbury Fields guidelines, benefits from an officer's view before the drawings are finished. Islington's planning pre-application fees increased on 2 January 2025, so check the current charge before booking.
How does Islington's building control charge work for a small rear extension?
Islington's Table 1 domestic charges price an extension up to 40 sq m as one item, split into a plan charge and an inspection charge under full plans. The floor area on the drawings therefore decides which line of the table your extension falls under. We measure it from the architect's plans before the application is made, so the charge matches the building and the inspections are booked against the right application.
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