House Extensions Brent
Single storey rear and double storey extensions in Brent, 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 Brent, working with the borough's mansion blocks, interwar semis and Victorian terraces in NW2, NW9, NW10 and HA0. We take a rear, side-return or wrap-around extension from foundations and steelwork through to a fully fitted finish.
In Brent, 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 Brent: 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 Brent
Brent range: choose above
Rear and side-return extensions in Brent
The interwar semis around Wembley and Kingsbury and the Victorian terraces of Willesden and Harlesden lend themselves well to extending. On a semi, a single storey rear kitchen extension is usually the way to a proper kitchen-diner; on a terrace, a side-return infill captures the wasted alley beside the kitchen, and a double storey rear extension adds a bedroom above where planning allows. We dig and pour the foundations, install the steel beams that carry the opening, build up the walls and tie the new roof into the existing one.
Ground conditions vary across Brent, and nearby trees or made-up ground can mean deeper or wider foundations, which the engineer we appoint specifies. Where your semi shares a boundary or party wall with the neighbour, the Party Wall Act usually applies and you, as building owner, serve notice early, using the drawings we supply. We then handle the full fit-out, so the new space is ready to use rather than a shell.
Housing in Brent
Around 135,080 homes make up Brent on the valuation list; 62% are flats and 38% houses, and 28% date from before 1919, 32% from between the wars and 40% from after 1945. Since most homes here are flats, a flat in Brent has no householder permitted development rights, so extending one needs planning permission and the freeholder's consent.
Brent extension depths are measured from the original rear wall
Brent's Residential Extensions and Alterations SPD allows single storey rear extensions to attached homes of up to 6 metres from the original rear wall. The same SPD says two storey rear extensions to attached homes must not be more than 3 metres deep from the original rear wall. The phrase that decides the design is original rear wall. On a house already extended once, the depth is counted from where the house first ended, not from the later kitchen wall. These are the depths Brent applies to a planning application; permitted development has its own limits. Find the original line in the planning history before anyone draws the new room.
Two building control points then settle the route. Brent requires a full plans application for extensions built over, or within, three metres of a public sewer, so a shared drain across the back gardens takes the building notice option away. Have the sewer located before the footprint is fixed. The second point is the Community Infrastructure Levy. In Brent, CIL relief for extensions to a home occupied by the applicant as their main residence is not automatic and must be applied for before commencement. Where it applies, the claim goes in before the first trench is dug, so the start date waits for it.
Planning and permitted development in Brent
Whether your Brent extension is permitted development or needs a full planning application to Brent Council depends on the property. Many houses in NW10 and HA9 can extend under permitted development rights within the size and height limits, but flats have no such rights, and homes on designated land or in a conservation area usually need a formal application. We assess your specific address before you commit.
If a planning application is the right route, we coordinate the drawings with your architect or designer and follow the submission to Brent Council, then move to building regulations for the structure, insulation, drainage and fire safety. Every extension needs building control inspection regardless of the planning position, and we book and attend those inspections so the work is signed off properly at completion.
Kitchen extensions in Brent
62% of homes in Brent are flats, and a flat has no householder permitted development, so a ground-floor flat's kitchen extension needs planning permission from Brent 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 Brent; the build figures are in the table above.
Double storey extensions in Brent
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 Brent often needs planning permission from Brent Council. It is a job for the 38% of homes that are houses; a flat cannot add a storey this way. Brent Council states that there are 22 conservation areas in Brent (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Drawings and the structural engineer's design coordinated for you
- Wrap-around extensions and infills
- Building control inspections at foundation, damp course and steel stages
VOA Council Tax stock of properties, March 2025, for all 35 statistical areas in Brent. Counts rounded by the VOA.
Why Brent Homeowners Choose GS Renovation
Homeowners across Brent trust GS Renovation to run the whole extension, from the first foundation to the final coat of paint, as one accountable project. We know when a Wembley semi qualifies for permitted development and when a flat or conservation-area home needs Brent Council's approval, and we plan around the party wall notices you serve, install the steel and manage building control throughout. Backed by our founder's 30+ years on the tools.
- Honest updates if a date or a detail has to move
- Brick and mortar matched to the existing elevation
- Weathertight shell reached before the fit-out begins
Reviewed jobs near Brent
1 MyBuilder review from Wembley, with each customer's own job title:
- Install new worktop, Wembley, 10 Jul 2024 (5 out of 5)
Read all 31 on our reviews page.
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 Brent
Why do house extensions quotes in Brent vary so much?
House extensions quotes in Brent spread widely because scope, not skill, is what differs. A figure that omits the engineer's design, the Brent Council building control fee or the making good will always undercut one that includes them. Sequence is where cheap quotes cut corners: the steel into the house is designed before the rear wall comes down. GS Renovation lists each element for the HA9 address against £2,000 to £2,800 per m² for a rear extension (indicative).
Can I extend my Wembley semi without planning permission?
Often yes. Many houses in Wembley and the wider HA9 and NW9 area can extend under permitted development, provided the size, height and boundary limits are met and the property is not a flat, though conservation areas restrict some rights. We check your exact address against the rules first, and if a full planning application to Brent Council is needed, we coordinate it with your architect or designer.
Can I extend my Brent ground-floor flat without a planning application?
No. Permitted development rights for rear extensions belong to houses, not flats or maisonettes, so a flat extension goes to Brent Council as a full application. The lease is a second gate, since it may not include the garden or outside walls, and the freeholder's written consent is needed. Building regulations then apply just as they would to a house, from foundations to insulation.
Why might a Brent extension need wider or deeper foundations?
Made-up ground and trees. Parts of Brent sit on filled or disturbed soil, and roots from nearby trees dry the ground beneath, so the engineer may call for deeper trenches, a wider footing or a reinforced design once trial holes show what is there. Digging within 3 metres of the attached house, below its footings, also needs a month's party wall notice before the first spade goes in.
Does a manhole in my Brent garden affect where the extension goes?
It can decide it. A chamber inside the footprint tells you a drain passes beneath, and if that pipe is a public sewer, Part H makes the water company's written agreement a condition of building on or beside it. The run may be diverted round the new walls, or the chamber moved outside the footprint and the pipe bridged. A camera survey of the drains at design stage shows which applies.
Will a glass roof on my Brent extension pass Part L?
It can, but glazing is the weakest part of any insulated envelope, so a large lantern or fully glazed roof has to be balanced elsewhere. The new walls, floor and solid roof are insulated to current Part L standards, and a heavily glazed design may need calculations showing the whole extension performs. Rooflights set over the old rear wall line push light deepest into the house.
Does a public sewer behind a Brent house rule out a building notice for an extension?
Yes, if the extension is over it or within three metres of it. Brent requires a full plans application in that case, so the quicker building notice route is closed. Check before choosing a route. A drain that serves more than one house is usually a public sewer, and on a terrace it can run under several gardens. A CCTV drainage survey shows its line and depth, and the water company's consent for building near it is a separate step.
What must be done about CIL before a Brent extension starts on site?
If the extension is liable, the relief claim comes first. The Brent CIL Charging Schedule came into effect on 1 July 2013, and relief for an extension to a home the applicant lives in as their main residence is not automatic. It must be applied for before commencement. Digging foundation trenches counts as starting, so hold the start date until the claim is lodged, and keep the acknowledgement with the planning papers.
How deep can a single storey rear extension go in the Willesden Green Conservation Area?
Brent's Willesden Green appraisal says a single storey rear extension beyond the original rear wall by more than 4m for a detached house, or 3m otherwise, needs planning permission in a conservation area. The area was designated in January 1993 and has a non-immediate article 4 direction. Measure from the original rear wall, not from a later addition, and assume an application for anything deeper.
Every Service, One Team
More GS Renovation Services in Brent
One team for every GS Renovation service in Brent:
Same Service, Nearby Areas
House Extensions Near Brent
We carry out house extensions across Brent and the surrounding areas. Explore a nearby location:
Ready to Start Your Brent Project?
Free, no-obligation quote for house extensions in Brent.