House Extensions Maidenhead
Single storey rear and double storey extensions in Maidenhead, planning, structure and build under one contract.
- Rated 4.9 from 31 reviews on MyBuilder
- Guide from £40,000 (London-derived)
- Free site survey, itemised quote
An extension in Maidenhead needs two approvals rather than one: planning, and building regulations. We build the extension, coordinate the building regulations side and work alongside your architect or designer on planning, and we appoint a structural engineer for the calculations rather than producing them. This page sets out what the town's planning framework has asked for since April 2026, what the ground under the town is, and what the council's own charges come to.
For Maidenhead, on London-derived ranges a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m²; Berkshire work generally runs below that. GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Maidenhead: the structural engineer we appoint designs the structure, we build it, and building control signs it off.
Price guide
| Work | Indicative 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. Berkshire work generally runs below the London figures; your price follows a site visit. Prices checked September 2026. Full breakdown: Extension Costs & Planning.
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The Maidenhead Neighbourhood Plan now helps decide your application
The Maidenhead Neighbourhood Plan was formally made, meaning adopted, by the Royal Borough of Windsor and Maidenhead on 21 April 2026. It now forms part of the statutory development plan used to decide planning applications in the town. An extension designed against the borough plan alone is no longer designed against the whole of the plan that applies to it.
Policy DE-2 requires development proposals to demonstrate full regard to the key characteristics of the relevant character area, and to follow the design guidance and codes for that area set out in section 4 of Appendix 1. That means identifying your character area before the drawings are produced rather than after. We raise it at the first visit. It applies whether the scheme is a single storey rear kitchen extension, a side extension or a two storey addition. A single storey rear extension within permitted development limits needs no planning application at all, while a side extension in a conservation area, and most two storey or multi storey extensions, do.
Housing in Maidenhead
The valuation list shows roughly 26,980 homes in Maidenhead, of which 12% are pre-1919, 8% interwar and 78% post-1945, split 33% flats to 67% houses. 24% of homes here are detached; a detached house in Maidenhead often extends far enough from the boundary that no party wall notice is needed.
The council will not let you correct an application after it is validated
The council's published position is not to seek or accept amendments to a planning application after validation. It states that it will not accept unsolicited amendments, and that where an amendment is accepted at officer discretion it will allow only one round. There is no comfortable second attempt built into the process.
The Royal Borough of Windsor and Maidenhead also adopted its National and Local Validation Requirements on 5 February 2026, and an application that does not meet them cannot be made valid. Getting the submission complete first time is therefore the whole game. We work through the buildability questions before anything is sent rather than after a refusal.
Foundation design in Maidenhead depends on which side of town you are on
British Geological Survey 1:50k mapping shows Seaford Chalk and Newhaven Chalk Formation, undifferentiated, as the bedrock across a long list of Maidenhead addresses. Those include the town centre, Boyn Hill, Castle Hill, Furze Platt, North Town, Ray Mill, Oaken Grove, Altwood Road, Pinkneys Green and the northern part of Cox Green. That is a different foundation problem from the clay ground further into London.
The same mapping shows Lambeth Group clay, silt and sand as the bedrock beneath the southern part of Cox Green and the Larchfield Road area. It also underlies the Lee Lane and Pinkneys Drive end of Pinkneys Green, and the southern fringe of Braywick towards the A308. Lambeth Group clay is shrinkable, so tree influence and seasonal ground movement matter on those sides of town. Braywick Road, Braywick Park and Desborough Park sit on chalk.
The building control charge for a single storey extension is published
From 1 April 2026 the council's building control charge for a single storey extension of 10 to 40 square metres is a £432.00 plan charge plus a £558.00 inspection charge on full plans, or £1,138.50 as a building notice, inclusive of VAT. That is separate from the planning fee, the engineer's fee and the build cost, and it is shown separately in your quotation.
The council asks for two days' notice before commencement of work, and one day's notice for stages including excavations for foundations, foundation concrete, damp proof course laid, first floor joists and roof timbers before covering. Those inspections are what a completion certificate rests on. We book each one as the build reaches it rather than afterwards.
Kitchen extensions in Maidenhead
67% of the houses in Maidenhead 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 Maidenhead; the build figures are in the table above.
Side return extensions in Maidenhead
Side returns belong to Victorian and Edwardian terraces, and only 12% of homes in Maidenhead predate 1919, so they are the exception here; most extensions run across the full rear width instead. Our side return extension page covers the build in detail, with build rates of £2,400 to £3,200 per m².
Double storey extensions in Maidenhead
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 Maidenhead often needs planning permission from Royal Borough of Windsor and Maidenhead. With 45% of homes here semi-detached or detached, the side of the house is often an option too. Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.
- Steel goalpost frames where the rear wall opens up
- Drawings and the structural engineer's design coordinated for you
- Flat and pitched roofs with rooflights or lanterns
VOA Council Tax stock of properties, March 2025, for all 7 statistical areas in Maidenhead. Counts rounded by the VOA.
Why Choose GS Renovation in Maidenhead
An extension here is decided against the Maidenhead Neighbourhood Plan as well as the borough plan, and the council does not accept unsolicited amendments once an application has been validated. That puts the effort at the front of the job, where it is cheapest. We identify the character area, appoint the structural engineer, work alongside your designer on the planning application, coordinate the building control application, and book each inspection as the build reaches it. You deal with one point of contact from the first survey to the completion certificate. GS Renovation Ltd is fully insured, registered in England, company number 14611254, and quotations are free and without obligation.
- Founder with 30+ years of hands-on experience
- Programme planned around party wall notice periods before excavation near a neighbour
- Drainage diverted or built over with the right approval in place
Built a new extension at rear of property. Laid foundations, drainage, raised floor, new roof and completed all fixtures and interior decoration…
Saiid did a complete refurbishment of our small bathroom. This involved ripping out the existing bath/shower, basin, toilet, pipework, and tiles and…
George is a very hard working builder, and has done a fantastic job on replacing my Bathroom. His attention to detail was great and I wouldn't…
FAQ
Frequently Asked Questions about House Extensions Maidenhead
What drives the cost of house extensions in a Maidenhead home?
Three things drive the cost of house extensions in a Maidenhead home within £2,000 to £2,800 per m² for a rear extension (London-derived): how much structure is involved, access at the SL6 address, and making good afterwards. The biggest variable is usually hidden: the drainage run under the footprint decides the foundations. GS Renovation prices each of the three separately rather than averaging across Maidenhead.
Who gives permission to build an extension over a public sewer in Maidenhead?
Thames Water does, as the statutory sewerage undertaker for the whole borough. A build over agreement is its decision rather than the council's, and it runs alongside planning and building regulations instead of replacing either one. We establish where the drainage runs before the footprint is fixed, because a sewer under the proposed slab changes the design rather than the finish. The position of the run is checked at the survey, not once the drawings are done.
The garden runs down to the Thames. Does the Environment Agency have to consent to an extension?
Its prior consent is required for works or structures in, under, over or within 8 metres of the top of the bank. The council's Maidenhead Riverside appraisal records the River Thames as a Main River, and cites the Water Resources Act 1991 and the Thames Land Drainage Byelaws 1981 for that requirement. It runs in parallel with planning permission and building regulations, so all three are identified at the survey.
The house is in the Altwood character area. How large can a rear extension be?
The design code sets a relationship rather than a size. Code CA8.07 states that in the case of building extensions in the Altwood character area, the original building should remain the dominant element of the property regardless of the scale or number of extensions. A second or third extension is therefore judged against the original house rather than against what was added last. We design to that before drawings are submitted.
Is a dormer or an extension that breaks the roofline a problem in Pinkneys or Oaken Grove?
The design code names it as a force for change in those character areas. Extensions that breach the building line or the roofscape are listed that way for Boyn Hill, Pinkneys and Oaken Grove. In Pinkneys and Oaken Grove, attic extensions with dormer windows are named among them. That does not rule a dormer out. It means the building line and the roofline are the first things your design has to answer.
How deep will the footings go on Boyn Hill?
Deep enough to reach ground the engineer accepts, and that depth is found by digging rather than predicted. The British Geological Survey gives the Boyn Hill Gravel Member a thickness of 1 to 9 metres, averaging 5 metres. It describes the member as poorly sorted stratified gravel with locally tabular cross bedded sand beds, resting unconformably on bedrock. Its reference exposure for the whole of Britain is a section near the cemetery on Boyn Hill.
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