House Extensions Holloway
Single storey rear and double storey extensions in Holloway, 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 plans and builds extensions across Holloway, adding space to N7's Victorian and Edwardian houses, a minority in an area of flats. We handle everything from foundations and steelwork to the roof and fit-out, whether you are infilling a side return, extending to the rear, or wrapping around into a kitchen-diner.
In Holloway, 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 Holloway: 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 Holloway
Holloway range: choose above
Side-return extensions on Holloway terraces
The side return is the strip of open ground beside the rear closet wing, and on a Holloway terrace it is usually wasted space. Filling it in widens a cramped galley kitchen into a full-width room that runs across the back of the house. We dig new foundations next to the existing walls, build up in brick or block, and carry the original rear wall on a steel beam so the ground floor opens right out.
Many rear and side-return extensions on Holloway terraces fall within permitted development, which means they can go ahead without a full planning application. Others need planning permission from Islington Council, especially where the property sits in a conservation area, is larger than the permitted limits, or affects the front elevation. We assess your specific house early and advise which route applies; your architect or designer then prepares the lawful development certificate or planning application, and we can recommend one and coordinate it.
Housing in Holloway
Roughly 10,640 dwellings sit on the valuation list for Holloway. 10% are houses and 90% flats, and by age 40% predate 1919, 6% are interwar and 50% post-war. Where most homes are flats, a flat in Holloway has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Extending a Holloway ground floor flat over the shared drain
An extension to a flat needs a full planning application in Islington, and in Holloway 90% of homes are flats. Planning is only half the paperwork. Behind a converted terrace the drain from every flat in the house can run under the garden where the extension would sit, and Islington says a building notice cannot be used when building over existing sewers and drains. The build then goes in as a full plans application, and a shared drain also needs the sewerage company's consent to build over or divert it, so a drainage survey comes before any design is drawn.
A camera survey shows the line, depth and condition of the drain, and tells the structural engineer we appoint whether the foundations can bridge it or the run has to move. In a house of flats that diversion affects the other owners, so it is agreed with the freeholder and written into the licence to alter. We aim to connect the new section in a single day with the upstairs flats warned, because the stack is out of use while it is done. Settling this at design stage stops a Holloway extension halting once the trenches are open.
Double-storey extensions in N7
Adding a second storey over a rear extension gives a Holloway family an extra bedroom or bathroom without moving out of the area. Because the new upper floor loads back onto the existing terrace, foundations and steelwork are designed to carry the additional weight, and the party wall almost always comes into play. We coordinate the structural engineer, the party wall surveyor and building control so the whole build stacks up safely on the original Victorian footings.
A double-storey extension is more likely to need planning permission than a modest ground floor addition, so we look at Islington Council's local policies before drawing anything up. Once consent and building regulations approval are in place, we manage the full programme, from groundworks and structure through to the roof, windows, plastering and decoration. You deal with one team throughout, and the new rooms are finished to match the proportions and character of the existing house.
Kitchen extensions in Holloway
90% of homes in Holloway 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. With so few houses here, the realistic kitchen gain in most Holloway homes is a better layout inside the flat rather than an extension. The fit-out is priced on its own page, kitchen renovation in Holloway; the build figures are in the table above.
- Steel goalpost frames where the rear wall opens up
- Full fit-out, finishing and making good
- Building control inspections at foundation, damp course and steel stages
VOA Council Tax stock of properties, March 2025, for Holloway Nag's Head and Lower Holloway. Counts rounded by the VOA.
Why Holloway Homeowners Choose GS Renovation
Holloway homeowners choose GS Renovation for extensions because we take the project from first sketch to final coat of paint, coordinating the planning route with your designer, programming around the party wall notices you serve, and building the structure and fit-out as one accountable job. With our founder's 30+ years on the tools, we know how Islington's period houses behave and how to add space that feels part of the original home.
- Building control applications and inspections coordinated for you
- Brick and mortar matched to the existing elevation
- 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…
George always kept to commitments and arrived on time. He offered helpful suggestions during his initial visit and promptly provided a reasonably…
It's the second time I have hired George and he has been absolutely professional and the work he did resembles perfectly what I had in mind. Being an…
FAQ
Frequently Asked Questions about House Extensions Holloway
How do you price house extensions in Holloway?
Pricing house extensions for a Holloway property starts with an N7 survey and ends with a written figure inside £2,000 to £2,800 per m² for a rear extension (indicative). The key physical check comes first: the depth of neighbouring Holloway foundations decides how deep the new footings go. The quotation then splits into structure, services and finishes, with building regulations approval from foundations to completion shown separately.
Do I need planning permission to extend my Holloway house?
Many rear and side-return extensions on N7 terraces are permitted development and need only building regulations approval. However, larger extensions, work in a conservation area, and anything affecting the front of the house usually require planning permission from Islington Council. We check your specific address at the outset and coordinate whichever application is needed with your designer before building work starts.
Can I extend my ground-floor flat in Holloway?
Possibly, but permitted development rights belong to houses, not flats. With 90% of Holloway homes being flats, most extensions here need a full planning application to Islington Council, the freeholder's written consent under the lease, and often the agreement of flats above whose windows face the garden. Building regulations then apply to the build itself. Check the lease before commissioning drawings.
Why does opening the back wall of a converted Holloway house need heavier steel?
Because that wall carries the flats above, not just your ceiling. In a Victorian Holloway house divided into flats, the rear wall supports every storey and often part of the roof. Opening it into an extension means an engineer-designed beam, sometimes with posts, carrying all of that load, and the building is propped floor by floor. The freeholder must consent, and building control inspects the bearings.
Does digging near my neighbour's house matter for a Holloway extension?
Yes, if you go below their foundations within 3 metres. On tight Holloway terraces the new footings usually run hard against next door, and digging that deep there obliges you to give the owner one month's written warning. They reply by agreeing or by dissenting, the second route ending in an award drawn up by surveyors. Sending it with the planning application keeps both clocks running together.
What building control inspections does a Holloway extension have?
Inspections come at stages where the work is about to be hidden: foundation trenches before concrete, drainage before backfilling, the damp-proof course, steel bearings where the old wall is opened, and insulation before boarding. After the final visit Islington Council issues its completion certificate. Part L applies to the new fabric only, so the extension's walls, roof and slab reach today's insulation values while the original house is left as it is.
Which Islington building control category covers a Holloway 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 ground floor extension behind a Holloway terrace is measured against that size at design stage. Under full plans the charge is split between plan checking and inspection, so part is paid when the drawings go in and the rest covers the site visits.
Does a tree need notice before a Holloway extension in a conservation area?
Yes, where the tree has to be pruned or felled. The Mercers Road/Tavistock Terrace conservation area takes in predominantly residential side streets off Holloway Road. 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. Branches over the footprint count. Giving notice while the drawings are prepared lets those weeks run alongside planning instead of delaying the start.
Does Islington's six week party wall guidance apply to a Holloway extension?
It applies where the Party Wall Act 1996 does. Islington's building control FAQ page says that if the Act applies you must notify your neighbours at least six weeks before you start the work, and the Act sets its own periods for each type of notice. For an extension the usual triggers are foundations dug close to and below next door's, or a wall built on the boundary. The building owner serves the notices, and Islington Council says it is not involved in the preparation, review or monitoring of any Party Wall Agreement.
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