House Extensions Highbury
Single storey rear and double storey extensions in Highbury, 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 Highbury, adding space to the Victorian and Edwardian terraces near Highbury Fields without losing their character. We handle the foundations, the steelwork, the roof and the full fit-out, and guide you through permitted development or a planning application to Islington Council.
In Highbury, 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 Highbury: 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 Highbury
Highbury range: choose above
Side return extensions in Highbury
The side return is the strip of open ground beside the rear closet wing, and infilling it is the classic way to widen a cramped kitchen in a Highbury terrace. We dig new foundations next to the existing wall, tie the new structure in, and install a steel beam where the original external wall is removed. A glazed roof or rooflights bring light deep into the plan, turning a narrow galley into an open kitchen-diner.
Many single-storey rear and side-return extensions on Highbury terraces fall under permitted development, but this is not guaranteed. If you want a side-return infill in a conservation area, where side extensions are not permitted development, or the home has been extended before, or you want a larger footprint, a full planning application to Islington Council is likely. We assess your property first, then work with the designer who applies for a lawful development certificate or prepares the planning submission, so you build on a sound legal footing.
Housing in Highbury
By the valuation list's count, Highbury holds about 7,960 homes, 21% houses and 79% flats; by age, 55% were built before 1919, 4% between the wars and 37% since 1945. A flat in Highbury 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.
Highbury Fields conservation area limits on side and taller rear extensions
Highbury Fields conservation area (CA5) was designated on 07/01/1969, last amended on 05/02/1990, and its current design guidelines were adopted in January 2002. For an extension the guidelines are specific. Apart from properties listed in Schedule 5.6, planning permission for side extensions will not be granted. If your Highbury house sits inside the conservation area, the first check is whether it appears in Schedule 5.6, because that single line decides whether an extension to the side of the house is worth drawing at all. Paying a designer to develop a side scheme before that check is the most avoidable cost on an extension here.
The rear limits shape a two storey scheme in particular. The guidelines say full width rear extensions higher than one storey, or half width rear extensions higher than two storeys, will not normally be permitted. A full width addition therefore stays at one storey, while a half width addition of up to two storeys is not ruled out by that wording. On a Highbury terrace with a closet wing, that points to a single storey infill across the full width, with any upper floor kept within the half width of the wing. Where a scheme sits near those lines, Islington's householder pre-application written advice gives a written view before the full application goes in.
Double storey extensions across Highbury
A double-storey rear extension adds a bedroom or bathroom above a bigger kitchen, and on many Highbury terraced plots there is room to do it well. We form deeper foundations to carry the extra load, build in brick or blockwork to match the existing elevation, and install steel beams at each floor. The rear closet wing can be squared off or wrapped around to create a coherent, larger footprint.
Extensions on shared boundaries bring the Party Wall etc. Act into play, since digging near or building against the neighbour's wall requires notice. In N5 you serve these notices as building owner; we coordinate with Islington building control for the foundations, damp proofing, insulation and structure, and manage the roof, glazing, plastering and decoration. You deal with one team from the first trial hole to the final coat of paint.
Kitchen extensions in Highbury
79% of homes in Highbury 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 21% of homes that are houses. The fit-out is priced on its own page, kitchen renovation in Highbury; the build figures are in the table above.
- Side-return and rear extensions
- Party wall process explained, and the extension built to the award
- First fix and second fix plumbing and electrics throughout
VOA Council Tax stock of properties, March 2025, for Highbury and Highbury Fields. Counts rounded by the VOA.
The GS Renovation Difference in Highbury
Homeowners in Highbury choose GS Renovation because we build extensions end to end, from groundworks and steel to the finished kitchen inside. We know how N5's terraces behave, when a scheme is permitted development and when Islington Council needs a planning application, and how to plan around the party wall notices you serve so neighbours stay onside. Our founder's 30+ years of work stands behind every project.
- Drainage diverted or built over with the right approval in place
- Free follow-up visit after completion if anything needs attention
- Building control inspected at foundation, damp course and steel stages
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
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…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
FAQ
Frequently Asked Questions about House Extensions Highbury
Is the price of house extensions higher in Highbury than elsewhere in North London?
The price of house extensions in Highbury is set by the housing rather than the postcode, within £2,000 to £2,800 per m² for a rear extension (indicative). Older construction takes more making good than recent work, and access at N5 affects the labour line. GS Renovation prices the property in front of it, because the drainage run under the footprint decides the foundations, rather than applying a Highbury multiplier.
Will my Highbury extension need planning permission or is it permitted development?
Many single-storey rear and side-return extensions in Highbury are permitted development, but a side-return infill in a conservation area, previous extensions or a larger footprint can push you into a full planning application to Islington Council. We assess your N5 home, confirm the route, and work with your designer on a lawful development certificate or the planning submission.
Can the owner of a ground-floor Highbury flat extend into the garden?
Possibly, but not under permitted development, which applies to houses and never to flats. An extension to a flat needs a planning application to Islington Council, and the freeholder's written consent under the lease. Check who actually owns the garden, as it is not always part of the flat's lease. Building regulations apply once planning and consent are in place.
How is the side return of a Highbury house infilled without disturbing next door?
By sorting notices before digging. New footings along the boundary tend to sit lower than the adjoining house's and within 3 metres of it, so its owner gets a month's warning in writing; an objection brings in surveyors. Note that a house inside a conservation area loses its permitted rights to build out to the side. The engineer designs the footing next to the boundary so it does not undermine next door.
Can I live in my Highbury house while the extension is being built?
Usually, if the sequence is right. The new shell, roof and glazing go up while the old rear wall stays closed, so the house remains secure. The disruptive week or two comes when that wall is propped, cut out and replaced with steel, and the kitchen may be out of action. Planning a temporary kitchen elsewhere makes this far easier.
Where does the drainage go from a new Highbury extension?
Into the existing system, with falls designed under Part H. Drains often run under the space an extension will occupy, with a manhole near the back wall. If that pipe is a public sewer, the water company must agree before anything is built across or close to it. Rainwater from the new roof also needs a route, which is fixed before the foundations are dug.
Is there a tree rule to check before a Highbury extension's foundations are dug?
Yes, inside a conservation area. In an Islington conservation area you must give the Council six weeks notice in writing before any work is carried out to prune or fell a tree. Cutting back branches over the footprint, or a tree that has to come out, falls within that. Giving notice at design stage keeps six weeks of waiting off the start of the build, and the response can move the footprint or change the foundation design.
Which Islington building control category covers a typical Highbury rear extension?
Islington's Table 1 domestic charges have a category for an extension up to 40 sq m, and its current building control charges apply to all applications made under the Building Regulations 2010 from 27 October 2025. A single storey rear extension or side infill on a Highbury terrace is measured against that size at design stage, so the application is made under the right heading and the fee is known before work starts.
What happens if a Highbury rear extension is built over the drain?
It changes the building control route. Islington Council says a building notice cannot be used when building over existing sewers and drains, so an extension that covers the drain run goes in as a full plans application. Behind a Highbury terrace the drain from the closet wing can run under the very ground the extension will cover. A drainage survey before design shows the route, and it lets the engineer detail the foundations around it or plan a diversion.
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