House Extensions Edgware
Single storey rear and double storey extensions in Edgware, 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 throughout Edgware and HA8 to your designer's approved drawings, making the most of the generous plots that came with its 1930s and interwar houses. We handle everything from single-storey rear additions to double-storey and wrap-around builds on these suburban semis and detached homes.
In Edgware, 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 Edgware: 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 Edgware
Edgware range: choose above
Rear and side extensions in Edgware
Edgware's interwar semis and detached houses were built on generous plots, which gives real scope for extending. A single-storey rear extension opens the back of the house into a large kitchen-diner, while a side return or side infill uses the space alongside the house that many 1930s plots enjoy. A wrap-around combines both, and a double-storey extension can add a bedroom and en-suite above the new ground-floor room. A home extension in HA8 is usually one of these four, and a kitchen extension across the back of the house is the most common.
We start with the groundworks, digging and pouring foundations suited to the local ground and any nearby trees, then build the walls, install the steel beams that carry the openings, and complete the roof. Throughout, we manage the full fit-out, including plastering, electrics, plumbing, flooring and decoration, so your Edgware extension is finished properly rather than left as a shell for other trades.
Housing in Edgware
Edgware has around 18,930 homes on the Council Tax list: 41% post-war, 57% interwar and 2% predate 1919, with 38% flats and 62% houses. 39% of homes here are semi-detached; a rear extension on a semi in Edgware digs beside the attached neighbour, so one party wall notice is usual.
Air bricks, the levy and an Edgware rear extension
The junction between the new floor and the old house decides whether an Edgware extension stays dry. 57% of homes here were built between 1919 and 1939, and a house of that age normally has a suspended timber ground floor kept dry by air bricks in the outside walls. A rear extension can bury those air bricks and leave the void with no through draught, which is how joists start to rot years after the builders leave. The answer is sleeved ducts through the new slab to fresh air bricks in the extension wall, or extra vents on the flanks, with the new damp proof course set to line up with the old one. We mark every air brick on the survey drawing so the designer plans for them.
The second check is financial, and on the Barnet side of the High Street it is Barnet's levy. Barnet Council was one of the first London authorities to adopt and implement the Community Infrastructure Levy, in May 2013, and its revised charging schedule came into effect on 1 April 2022. An ordinary single storey addition is normally below the size at which a householder extension becomes liable, but a large wrap-around or two storey scheme should have its position confirmed before work starts. Where an exemption has to be claimed, the claim must reach the council before work starts, and starting on site first can lose it.
Planning and permitted development in HA8
Whether your Edgware extension needs a full planning application or falls under permitted development depends on the property. Many single-storey rear extensions on interwar semis can proceed under permitted development rights, subject to size, height and boundary limits. Larger builds, double-storey additions, side extensions in a conservation area, work to a listed house, or a property with restricted rights usually require a full planning application to Barnet Council, or to Harrow Council for homes on the Canons Park side, west of the High Street.
We assess your specific house and plot before committing to a route, and where an application is needed your architect or designer prepares and submits it, and we build to the approved drawings. The structural work is covered separately by building regulations, with building control inspecting the foundations, steel and drainage. Where an extension sits near or on the shared party wall of a semi, you serve party wall notices on your neighbour (or your surveyor does), and we give you the drawings they need.
Kitchen extensions in Edgware
81% of the houses in Edgware are semi-detached or detached, which usually leaves room for a kitchen extension across the full rear width, with a steel beam over the opening into the house. The fit-out is priced on its own page, kitchen renovation in Edgware; the build figures are in the table above.
Double storey extensions in Edgware
Under permitted development a two-storey rear extension can go no more than 3 metres beyond the original rear wall and must stay at least 7 metres from the rear boundary, and in a conservation area it is not permitted development at all. Many gardens are too short for the 7 metre rule, so a double storey extension in Edgware often needs planning permission from Barnet Council or Harrow Council. With 50% of homes here semi-detached or detached, the side of the house is often an option too. The national Planning Data service returns 16 conservation area results for the London Borough of Barnet, including Railway Terraces (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Insulation, airtightness and thermal detailing to regulations
- Wrap-around extensions and infills
- Trial holes to set foundation depth near drains and trees
VOA Council Tax stock of properties, March 2025, for all 5 statistical areas in Edgware. Counts rounded by the VOA.
Why Choose GS Renovation in Edgware
Edgware homeowners choose GS Renovation because one team takes the extension from foundations to final coat. We advise honestly on permitted development versus a planning application to Barnet Council, or Harrow Council west of the High Street, install engineer-sized steel, coordinate building control and finish the space fully. With our founder's 30+ years on the tools, we understand these interwar plots and how far they can go.
- Programme planned around party wall notice periods before excavation near a neighbour
- Dust screens and floor protection in occupied homes
- Garden levels and access made good where the build meets outside
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
The kitchen has been fitted to the high standard. Saaid was polite, professional, tidy, he pays attention to a little details that make huge…
Saiid did a complete refurbishment of our small bathroom. This involved ripping out the existing bath/shower, basin, toilet, pipework, and tiles and…
FAQ
Frequently Asked Questions about House Extensions Edgware
Does the cost of house extensions rise in a 1930s suburban Edgware property?
In a 1930s suburban Edgware home the unknowns behind plaster are what move a house extensions figure within £2,000 to £2,800 per m² for a rear extension (indicative), which is why the HA8 survey matters more there. GS Renovation prices the visible work, names the risks, and agrees anything additional in writing. The approvals do not change with age: building regulations approval from foundations to completion applies either way.
How far can a single storey rear extension go on an Edgware house?
On the Barnet side of the High Street, Barnet's draft design guidance sets 3 metres for a terraced house, 3.5 metres for a semi detached house and 4 metres for a detached house. Policy CDH05 then asks that extensions complement the character of the existing building in style, form and materials and stay subordinate in size, scale and height. It also requires a sympathetic roof profile and amenity space kept above the Table 10 standard. Permitted development can allow more, but the two routes are assessed differently.
Do trees near the boundary change the foundations for an extension?
Yes, tree roots in shrinkable London Clay govern foundation depth, and a protected tree adds a consent step on top. Tree preservation orders are common across Edgware, so check the council's register for your address before planning footings near a mature tree. British Geological Survey mapping shows London Clay bedrock across Edgware, so footings near a mature tree are deepened on the engineer's advice.
Does an extension near Edgware town centre need a flood risk assessment?
It can, because a flood risk point check at Edgware town centre returns both Flood Zone 2 and Flood Zone 3 records from the Environment Agency. Barnet's Local Plan confirms parts of the station site are in Flood Zone 3 and at surface water flood risk, and paragraph 4.18.10 describes the town centre as in effect surrounded by floodplains. Where a site falls in Zone 2 or 3, the application needs a flood risk assessment and finished floor levels set accordingly.
Is there made ground under Edgware gardens that could complicate footings?
None is mapped: British Geological Survey mapping across Edgware records no artificial ground at 1:50,000 scale and no superficial deposits except alluvium in the brook corridors. That does not remove the need for trial holes, since garden scale infill, old ponds and buried garden waste sit below the resolution of national mapping. The practical answer is that footings are designed on what the trial hole shows, not on the map.
Will an extension be refused on the Watling Estate?
Not automatically, but the conservation area appraisal lists additions and extensions among the unsympathetic alterations already harming the estate, alongside replacement windows and doors, added porches, cladding and rendering, dormers and roof extensions and fake timber framing. It also records front gardens set back behind low brick walls or hedges, with specimen trees planted on boundaries that open or terminate views. A rear extension that leaves the front boundary and street view untouched has the better chance.
Does Barnet's newer Local Plan change how an Edgware extension application is judged?
It sets the policy an application made now is judged against. The national Planning Data record gives the Barnet Local Plan document a start date of 4 March 2025, so an extension next door approved before then was assessed under earlier policy and is a weaker precedent than it looks. Ask your designer to check the current policies on extensions before the drawings are fixed, and to show in the application how the design meets them.
Could rebuilding the front wall after an Edgware extension need planning permission?
Sometimes. Gates, fences and front walls are normally permitted development within set heights, but an Article 4 direction can remove that right. Barnet has used one for exactly this: its direction in Glenhill Close Conservation Area, approved on 31 July 2002, covers the erection or alteration of a gate, fence, wall or other means of enclosure. If the extension needs a wider gate for skips and deliveries, or the front wall rebuilt afterwards, check whether a direction covers your street before anything is taken down.
Would making an Edgware extension into a self-contained annexe bring in the levy?
It can. Barnet's revised CIL charging schedule, adopted on 1 March 2022, sets a rate for residential development including the C3 use class, so an extension designed as a separate home is assessed differently from one that stays part of the house. An annexe for family use may qualify for an exemption, but that has to be claimed before work starts. Settle the intended use with your designer first, because it also decides whether planning treats the annexe as a new dwelling.
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