House Extensions Bexley
Single storey rear and double storey extensions in Bexley, 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 Bexley, making the most of the plots that came with the borough's 1930s and interwar semis. Homeowners in Bexleyheath, Sidcup and Welling call us to add space to family houses across DA5, DA6, DA7, DA15 and SE2. We handle everything from foundations to final fit-out.
In Bexley, 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 Bexley: 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 Bexley
Bexley range: choose above
Kitchen extensions and side returns in Bexley
Most extensions we are asked about in Bexley are kitchen extensions: the original kitchen of a 1930s semi is small and closed off, and a single-storey rear addition turns it into a kitchen-diner across the back of the house, with an extra room's worth of space. The wide side access on a typical Bexley semi also suits a side-return or wrap-around extension, filling the gap between the house and the boundary to widen the kitchen further. We dig and pour the foundations, build the cavity walls to match the interwar brickwork, and install the steel beams that carry the existing rear wall once it opens into the new space. A warm flat or pitched roof closes it in.
With planning permission, double-storey rear extensions suit the larger family homes around Danson Park and Hall Place, adding a bedroom and bathroom above a bigger kitchen-diner below. Foundations go deeper to carry the extra load, and we watch for the mature trees common on these older plots, which can affect the foundation design. Throughout, we protect the garden, keep the site tidy and sequence the trades so your home stays liveable while the build progresses.
Housing in Bexley
Bexley counts roughly 101,760 homes for Council Tax; 11% are older than 1919, 41% interwar and 48% post-war, with 27% flats and 73% houses. Semi-detached houses make up 36% of homes here, and a rear extension on a semi in Bexley digs beside the attached neighbour, so one party wall notice is usual.
Sizing a Bexley rear extension to the new Design Guide
Bexley adopted the Design Guide SPD Part 2, which includes Building Alterations and Extensions guidance, on 29 June 2026, so drawings for a planning application prepared before that date should be checked against it. It says an extension to a terraced or semi-detached dwelling should typically not exceed 3.5m deep, and a single-storey extension should not exceed 4m at its highest point, with an eaves height of no more than 3m. Where a Bexley semi needs planning permission rather than relying on permitted development, those limits decide whether a pitched roof with a useful internal ceiling fits, or whether a flat roof with a lantern gives more height inside for the same outline.
The floor area then sets the building control band. Bexley charges domestic extensions of more than 10m2 and less than 40m2 in one band and more than 40m2 and less than 60m2 in the next, so a scheme sitting just over a band edge is worth measuring again. In both bands the building notice charge equals the plan charge and the inspection charge added together, so the full plans route costs the same and gives you an approved design. For a Bexley extension that also carries steel into the house, that approval is worth having before the foundations are dug.
Planning and party walls in Bexley
Many single-storey rear extensions on Bexley's suburban plots fall under permitted development, meaning no full planning application, though flats and converted properties, side extensions on corner plots, and side or two-storey extensions in a conservation area need permission from Bexley Council. We advise early on which route applies, coordinate the drawings, and see the lawful development certificate or planning application submitted as needed. Either way, the structural work still needs building regulations approval and staged inspection.
Because the semis of DA5, DA6 and DA7 share a boundary and a party wall with the house next door, extensions frequently trigger the Party Wall Act. Digging foundations within three metres of the neighbour's wall, or building up to the boundary, means notice before work starts, which you serve as building owner. We give you the drawings the notices need, coordinate with your neighbours, and keep building control inspections booked at foundation, damp-proof and completion stages.
Double storey extensions in Bexley
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 Bexley often needs planning permission from Bexley Council. With 40% of homes here semi-detached or detached, the side of the house is often an option too. Bexley has 23 conservation areas across the borough and special controls apply to buildings in them (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Building control inspections at foundation, damp course and steel stages
- Drainage diversion and build-over agreements with the water authority
- Steel goalpost frames where the rear wall opens up
VOA Council Tax stock of properties, March 2025, for all 28 statistical areas in Bexley. Counts rounded by the VOA.
Trusted House Extensions in Bexley
Homeowners across Bexley choose us because one accountable team runs the whole extension, from the first foundation trench to the final coat of paint. We know how interwar semis are built, how Bexley Council handles planning, and where the party wall lines fall. With our founder's 30+ years on the tools, we deliver a watertight, well-finished extension without the finger-pointing of separate trades.
- Garden levels and access made good where the build meets outside
- Weathertight shell reached before the fit-out begins
- Materials priced at options, so you choose the finish
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
Giorgio is an excellent and intelligent workman, and with very reasonable prices! He installed a kitchen extractor fan in a complicated situation…
George was brilliant. Lovely bloke, very reasonably priced and a perfectionist to boot. He completed our small kitchen renovation with care and great…
FAQ
Frequently Asked Questions about House Extensions Bexley
Does the cost of house extensions rise in a mixed interwar and post-war Bexley property?
In a mixed interwar and post-war Bexley 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 DA6 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: a Bexley Council building control inspection of the foundations before concrete is poured applies either way.
Will my Bexley extension need planning permission or just building regs?
Many single-storey rear extensions on Bexley's generous semi plots are permitted development and only need building regulations, but larger builds, corner sites, flats and side or two-storey extensions in conservation areas need planning permission from Bexley Council. We assess your house early, tell you which applies, and handle whichever application is required alongside the building control sign-off.
Do trees near my Bexley garden affect how deep the extension foundations go?
They can. Clay-rich ground, noted around DA5 and DA15, swells and shrinks as roots draw moisture out, so foundations close to a mature tree may need to go deeper or be engineered differently. The engineer considers tree species, distance and soil before the design is fixed. Building control then checks the trench before concrete, which is the moment depth is confirmed.
What if there is a drain or manhole where my Bexley extension will sit?
It shapes the plan. A private drain can be rerouted with proper falls under Part H. If the pipe is a public sewer, often the case where it also serves the semi next door, building over or near it needs the water company's consent first. Surveying the drains before the drawings are final saves redesigning the footprint later.
Does digging foundations in Bexley mean telling the neighbours?
Often, yes. A footing trench that passes within 3 metres of next door and reaches lower than their own footings obliges you to give them a month's written warning under the 1996 Act, and walls built astride or against the boundary line carry notices of their own. Houses are 73% of Bexley's dwellings on the VOA count and most of them share a wall, so a rear extension is rarely far from next door's footings. The notice is served before the trench is dug.
Will the room behind my new Bexley extension end up dark?
It will lose its window, so light has to come from above. A rooflight or lantern positioned near the old rear wall draws daylight back into the middle of the house. The extension also has to meet current Part L insulation standards, which limits how much glazing the design can carry. Where the steel opening goes affects how far that light travels.
How quickly can Bexley decide a larger home extension prior approval?
If you pay Bexley's Fast Track fee for a Larger Home Extension prior approval, the decision comes within 20 working days of validation. The clock starts at validation, so a missing plan or neighbour address costs time. The larger home extension route is not available in a conservation area. Use those weeks for the drain survey, trial holes and the engineer's design, so building control can be applied for as soon as the prior approval decision arrives.
Will a Bexley extension have to pay the Community Infrastructure Levy?
Only a large one is likely to. Bexley states that development creating a new home or increasing floor space by over 100 square metres is likely to be liable to pay CIL. A single-storey rear extension on a semi falls well below that, but a wrap-around combined with a two-storey side addition can approach it. Measure the combined new floor space early, and if it is near the threshold, raise it with Bexley before building starts, since householder relief has to be claimed before work begins.
Can a front porch be added to a house on the Old Forge Way estate in Sidcup?
Plan on no. The Old Forge Way Conservation Area appraisal states that front porch extensions would not be appropriate in the style of the estate. That puts the extra space at the back or side of the house instead. A rear addition kept within Bexley's design guidance is a stronger application there than a porch, and the front of the house stays as the estate was designed.
Every Service, One Team
More GS Renovation Services in Bexley
One team for every GS Renovation service in Bexley:
Same Service, Nearby Areas
House Extensions Near Bexley
We carry out house extensions across Bexley and the surrounding areas. Explore a nearby location:
Ready to Start Your Bexley Project?
Free, no-obligation quote for house extensions in Bexley.