House Extensions Beckenham
Single storey rear and double storey extensions in Beckenham, 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 Beckenham, where most homes are flats and the houses range from Edwardian villas to interwar semis. We handle everything from foundations to the roof and full fit-out, and advise clearly on whether your project is permitted development or needs planning permission from Bromley Council.
In Beckenham, 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 Beckenham: 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 Beckenham
Beckenham range: choose above
Side-return and rear extensions in Beckenham
On a Beckenham terrace, the usual extension fills in the side return, widening a narrow kitchen into a bright, open-plan space. On the larger Edwardian villas we build full-width rear or wrap-around extensions, and on the interwar semis a double-storey addition can add a bedroom and en-suite above a new kitchen-diner. Each project starts with proper foundations and groundworks matched to the clay subsoil common across BR3.
Steel beams tie the new opening back into the existing structure, sized by the engineer we appoint and signed off by building control. We coordinate the roof works, whether a flat roof with rooflights or a pitched roof to match the original, then handle the full fit-out including plastering, electrics, plumbing and decoration. One team runs the whole build, so the extension reads as part of the house rather than a bolt-on addition.
Housing in Beckenham
Take the 13,510 or so homes the valuation list gives Beckenham: 62% flats, 38% houses, 24% from before 1919, 10% interwar and 65% post-war. Since most homes here are flats, a flat in Beckenham has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Upward extensions and side additions under Beckenham's planning rules
Adding a storey has its own rule in part of Beckenham. Bromley has an Article 4 Direction removing upwards extension rights under Part 1, Class AA and Part 20 for the View of Croydon Town Centre from Village Way, Beckenham. Its non-immediate directions of that kind came into effect on 15 March 2022. For a house covered by it, an extra storey that elsewhere would go through the prior approval process needs a planning application instead. Check the boundary of the direction with Bromley Council before any design fee is spent.
Side additions follow Bromley Local Plan Policy 8, which normally requires a proposal of two or more storeys to keep a minimum 1 metre space from the side boundary for its full height and length. 20% of Beckenham's homes are semi-detached or detached, and on those plots the metre decides whether a two-storey side extension gives a usable bedroom or only a box room. Measure the side passage at its narrowest point, front and back, before the designer is briefed, since boundaries are not always parallel to the house.
Planning and party walls in Beckenham
Many single-storey rear extensions on Beckenham houses fall under permitted development, but this is never guaranteed. Larger projects, anything to the front, and any extension where an Article 4 direction removes the rights will need a full planning application to Bromley Council. In a conservation area, side extensions and two-storey rear extensions need permission too, though a single-storey rear extension within the limits can still be permitted development. We assess your specific property first, then have the drawings prepared by the architect or designer we coordinate and manage the application where one is required, so you know exactly where you stand before any work begins on site.
Extensions on a Beckenham terrace or semi almost always engage the Party Wall Act, because you are building up to the boundary shared with a neighbour and excavating foundations near their wall. You serve the party wall notices as building owner. We give you the drawings they need, coordinate any surveyor involved and keep the adjoining owners informed. Separately, building regulations govern the structure, insulation and drainage, with building control inspecting at key stages through the build.
Kitchen extensions in Beckenham
62% of homes in Beckenham are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Bromley Council and the freeholder's consent. Most kitchen extensions here are on the 38% of homes that are houses. The fit-out is priced on its own page, kitchen renovation in Beckenham; the build figures are in the table above.
Double storey extensions in Beckenham
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 Beckenham often needs planning permission from Bromley Council. It is a job for the 38% of homes that are houses; a flat cannot add a storey this way. Bromley has an Article 4 Direction removing upwards extension rights under Part 1, Class AA and Part 20 for the View of Croydon Town Centre from Village Way, Beckenham (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- First fix and second fix plumbing and electrics throughout
- Drawings and the structural engineer's design coordinated for you
- Steel goalpost frames where the rear wall opens up
VOA Council Tax stock of properties, March 2025, for New Beckenham, Beckenham East & Kelsey Park and Clock House & Cator Park. Counts rounded by the VOA.
Trusted House Extensions in Beckenham
Beckenham owners choose GS Renovation because we join up the drawings, the planning or permitted-development route and the build under one roof. With our founder's 30+ years on the tools, we know the local plots, the clay subsoil and the Bromley Council process, and we finish with a tidy, fully signed-off extension.
- Weathertight shell reached before the fit-out begins
- Building control applications and inspections coordinated for you
- Foundation depth set after trial holes, drains and trees are checked
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
Giorgio is an excellent and intelligent workman, and with very reasonable prices! He installed a kitchen extractor fan in a complicated situation…
FAQ
Frequently Asked Questions about House Extensions Beckenham
Does the cost of house extensions rise in a post-war estate Beckenham property?
Age affects the cost of house extensions in Beckenham less than people fear; the structural part is broadly similar, within £2,000 to £2,800 per m² for a rear extension (indicative). What differs in post-war estate housing is making good plaster, skirtings and floor finishes around the BR3 works, priced as separate lines. The sequence also holds: drainage under the footprint is diverted before foundations are poured.
Will my Beckenham extension need planning permission or is it permitted development?
Many single-storey rear extensions on Beckenham houses are permitted development, but larger, double-storey or front extensions need a planning application to Bromley Council. In a conservation area side extensions need one too, though a single-storey rear extension within the limits stays permitted development unless an Article 4 direction removes it. We check your address and the size you want first, then handle the application if one is needed.
Can I extend a ground floor flat in Beckenham?
Occasionally, though not by the house route. Permitted development for rear additions belongs to houses, never flats, so a Beckenham flat goes straight to a full application with Bromley Council. Before that the freeholder must agree, since the garden and external walls are normally theirs under the lease. Building regulations then cover the new structure exactly as for any other extension.
How deep do extension foundations go on the clay under Beckenham?
Nobody can promise a depth off a drawing. BR3 clay swells in wet winters and shrinks in dry summers, and a nearby oak or poplar exaggerates that by drinking the ground dry, so the trench may go well down or become an engineered foundation. The inspector stands at the open trench and agrees the bottom before a single barrow of concrete goes in.
What if a sewer runs where my Beckenham extension will be built?
Then the water company gets a say before building control approves anything. Their consent is needed to build over or close to a public sewer, and they can insist on a camera survey, protection of the pipe or a diversion. That can shift the footings or shrink the footprint, which is why the drains behind a Beckenham house are traced at the very first visit.
What insulation standard does a new Beckenham extension have to meet?
Current Part L standards, not whatever the original house was built to. That covers the floor, walls, roof and glazing, and it can limit how much glass goes into a rear wall or roof lantern unless the rest is upgraded to compensate. The building control inspector checks the insulation as it goes in, so it is fitted before the plasterboard rather than argued about later.
Can a rear extension in the Chancery Lane conservation area be clad or rendered?
Not as permitted development. The Chancery Lane direction brings render and cladding on brickwork under planning control, but not where the work affects the rear of buildings. That exception does not free the back, because cladding any part of a house in a conservation area is outside permitted development anyway. A rendered or timber-clad rear extension there needs planning permission, while a brick one matching the house may not.
Is Bromley's written pre-application advice worth it for a Beckenham extension?
For anything beyond a simple rear addition, usually. Bromley's written pre-application advice for householder proposals, including extensions to an existing dwelling, is charged at a fixed fee including VAT, and it tests the design before the full application. It is most useful for two-storey side schemes close to the Policy 8 side space, or in Beckenham's conservation areas and Areas of Special Residential Character, where the design judgement is finer.
How do building control and party wall timings fit a Beckenham extension programme?
Bromley Council's building control service issues a full plans approval notice within five weeks, or two months where the period is extended by agreement. Excavation near adjoining buildings needs at least one month's notice under Bromley's party wall guidance. Send both in the same week, then use the waiting time to order steel and windows, which can have longer lead times than either approval.
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