House Extensions Pinner
Single storey rear and double storey extensions in Pinner, 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 Pinner, working with the interwar semis that make up much of HA5, its period terraces and cottages. Whether you want a rear kitchen extension, a side extension or a double-storey addition, we handle groundworks, steel and fit-out, and tell you honestly whether it is permitted development or needs Harrow Council planning.
In Pinner, 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 Pinner: 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 Pinner
Pinner range: choose above
Kitchen extensions to the side and rear in Pinner
On a Pinner semi the strip beside the house, often a drive or side passage, is where a single-storey side extension can widen a cramped kitchen, and on the older terraces near the village the side return beside the rear wing does the same job. We dig new foundations to suit the ground and any nearby trees, tie into the existing wall, and drop a steel beam across the old opening so the kitchen and the new space read as one bright room.
A full-width rear extension goes further, extending across the back of the house to create a kitchen-diner opening onto the garden. We manage the groundworks, damp-proofing, steel, roof (whether a warm flat roof with a lantern or a pitched tiled roof) and the glazing. Where the work is near a shared wall or boundary, you serve party wall notices on the neighbours before excavation starts, using the drawings we supply, so nothing stalls once we are on site.
Housing in Pinner
Take the 11,760 or so homes the valuation list gives Pinner: 36% flats, 64% houses, 18% from before 1919, 39% interwar and 43% post-war. A rear extension on a semi in Pinner digs beside the attached neighbour, so one party wall notice is usual, and 28% of homes here are semi-detached.
Larger rear extensions in Pinner and the neighbours' 42 days
46% of homes in Pinner are semi-detached or detached, which makes Harrow's prior approval route for larger rear extensions worth understanding here. Under that route, the depth allowed for a larger single storey rear extension goes from 3 metres to 6 metres on a terraced or semi-detached house, and to 8 metres on a detached one. That lets a deeper single storey rear kitchen extension go ahead without a full planning application, but only after the neighbours have had their say and the council has decided.
Immediate neighbours are consulted and the process can run for 42 days, so talk to next door before applying, show them the drawings and note any concerns about light or the boundary wall. The route is not available for a listed house or one in a conservation area, and Pinner has several, including Pinner High Street, Pinner Hill Estate, West Towers and Pinnerwood Park Estate. Run building control alongside: use the 42 days to get the structural calculations and the building regulations drawings ready, so the trench can be dug soon after the approval arrives.
Planning and permitted development in Pinner
Many single-storey rear extensions in Pinner fall under permitted development, but the rights are not unlimited, and parts of Pinner sit within conservation areas, where side, two-storey and roof extensions lose their permitted development rights. If your house is in one, is listed, or you want a larger or double-storey addition, you will need a full planning application to Harrow Council. We assess this at the outset so there are no surprises later.
Whichever route applies, the structural side is governed by building regulations, not planning, so foundations, beams, insulation and fire safety all need building control inspection and sign-off. We work with your designer on the drawings and applications and coordinate the engineer and building control together. On interwar semis we also watch daylight and boundary distances to neighbours, which often shape how far a side extension can reasonably go before it becomes a problem.
Double storey extensions in Pinner
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 Pinner often needs planning permission from Harrow Council. With 46% of homes here semi-detached or detached, the side of the house is often an option too. An Article 4 direction for all houses in West Towers Conservation Area, Pinner, requires planning permission for any other alteration to the roof, such as rooflights or new roof tiles (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
- Foundations, groundworks and steel frames
- Building control inspections at foundation, damp course and steel stages
VOA Council Tax stock of properties, March 2025, for Pinner Green, Pinner Central, Pinner Road and Pinner South. Counts rounded by the VOA.
Trusted House Extensions in Pinner
Homeowners across Pinner choose GS Renovation because we run the whole extension, from the first feasibility chat about permitted development through groundworks, steel to the finished kitchen. One team, one point of contact, and our founder's 30+ years on the tools. You get realistic advice on planning, tidy site management and a build that meets Harrow Council's requirements.
- Permitted development checked before you pay for a planning application
- Brick and mortar matched to the existing elevation
- 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…
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 Pinner
Which parts of a house extensions project in Pinner cost the most?
Which part of a house extensions project in Pinner costs most depends on the house, which is why the survey comes first. In older stock reinstatement often outweighs the structural element; a newer HA5 property is the other way round. GS Renovation prices the two separately within £2,000 to £2,800 per m² for a rear extension (indicative), so phasing is possible, provided the order holds: drainage under the footprint is diverted before foundations are poured.
Will my Pinner extension need planning permission or is it permitted development?
Many single-storey rear extensions on Pinner terraces and semis are permitted development, but if you want a double-storey or large addition, or a side extension in one of Pinner's conservation areas, you will likely need a planning application to Harrow Council, and a listed home needs listed building consent. Either way, the structure still needs building regulations approval. We assess both at the survey.
Can I build a side extension on a house in a Pinner conservation area?
Not under permitted development. Conservation areas remove permitted development rights for side extensions, so a planning application to Harrow Council is needed. A single-storey rear extension may still be permitted development, depending on the house. Building regulations approval is needed either way. We check the rules for your house before any design starts.
Will the trees near my Pinner house affect the extension foundations?
They can. Tree roots draw moisture from the ground, and foundations near trees often need to go deeper so they sit below the zone where the soil moves. The engineer takes into account the species, height and distance of nearby trees. Removing a tree can also cause problems as the ground recovers. This is assessed before foundations are designed.
When does building control inspect my Pinner extension?
At set points through the build. For a Pinner extension the inspector usually wants the open trench before it is filled, the new drains while still exposed, the damp course and floor build-up, and any steel before casing, then a final visit. Each visit has to be passed before work covers it, so we book them ahead rather than leaving trades idle waiting for a slot.
Can my kitchen move into the new extension in Pinner?
Yes, but the services have to follow. The sink waste and any dishwasher need a route to the existing drain with enough fall, the gas hob is moved by a Gas Safe engineer, and the extraction has to be ducted outside under Part F. New kitchen circuits are notifiable under Part P. We plan these runs into the extension floor before the slab goes in.
Can a house on Pinner Hill Estate be extended without a planning application?
Check before assuming so. An Article 4 direction confirmed on 19th July 1990 applies to all land within Pinner Hill Estate Conservation Area except its listed buildings. Ask Harrow's planners which permitted development rights it removes. If it covers enlargement, even a single storey rear extension that would be allowed elsewhere in a conservation area needs an application, and the prior approval route for larger extensions is not open there either. Build the planning time into the programme before the structural engineer we appoint starts the design.
Can a side extension on Pinnerwood Park Estate change the hipped roof?
Only with planning permission, and the extension needs it anyway, because side extensions are not permitted development in a conservation area. In the Pinnerwood Park Estate Conservation Area core area, Article 4 directions also require planning permission for roof alterations such as dormer windows, rooflights and gabling existing hipped roofs. A two storey side extension that turns the hip into a gable is the change those directions name, so a design that keeps the hip, or a single storey side extension under its own roof, starts from firmer ground.
What changes if a Pinner extension sits within 3m of a public sewer?
The application route. Harrow requires a full plans application, not a building notice, where an extension is to be built over or within 3m of a public drain or sewer. A building notice would let work start quickly, so losing that option adds an appraisal stage before the trench is dug. Locate the sewer early with a drainage survey, and apply for the water company's consent at the same time as the full plans, so neither holds up the start date.
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