House Extensions Leatherhead

GS Renovation builds house extensions in Leatherhead, from single storey rear kitchen extensions to two storey work, building to the structural engineer's calculations. The ground varies across the town: the London Clay Formation is mapped under Kingston Road north of the station, and River Terrace Deposits of sand and gravel at the western end of Randalls Road. The foundation follows what is there. Fully insured, with free no obligation quotations.

For Leatherhead, on London-derived ranges a single-storey rear extension typically starts from £40,000, or £2,000 to £2,800 per m²; Surrey work generally runs below that. GS Renovation Ltd, a building contractor based in Potters Bar, does the work in Leatherhead: the structural engineer we appoint designs the structure, we build it, and building control signs it off.

The ground decides the foundation, and it changes across Leatherhead

The London Clay Formation is mapped as the bedrock under Kingston Road north of the station and the western end of Barnett Wood Lane, with Head deposits over parts of it. Highlands Avenue, in south east Leatherhead, is different: it is mapped on chalk with no superficial cover. Two extensions of the same size on those two streets can need different foundations.

Randalls Road splits as well. River Terrace Deposits of sand and gravel are mapped in patches at its western end and westwards towards the Fetcham boundary, while the eastern half has London Clay bedrock with no superficial cover. Head, where it appears, is described by the British Geological Survey as gravel, sand, silt and clay accumulated by downslope solifluction, soil creep and hill wash.

Housing in Leatherhead

Around 6,970 homes make up Leatherhead on the valuation list; 44% are flats and 56% houses, and 14% date from before 1919, 16% from between the wars and 69% from after 1945. A detached house in Leatherhead often extends far enough from the boundary that no party wall notice is needed, and 19% of homes here are detached.

Flood risk in Leatherhead follows the River Mole

Environment Agency flood risk here is confined to a narrow corridor along the River Mole. It takes in Leatherhead Bridge and the western end of Bridge Street, the southern end of Waterway Road, and the Fetcham Grove and leisure centre land beside the river. The eastern end of Young Street is in Flood Zone 2 only.

The boundary runs tight to the water. Leatherhead Bridge and the western end of Bridge Street, on and beyond the river crossing, fall within Flood Zone 3. The town centre stretch of Bridge Street, east of about the Running Horse, lies outside both Flood Zone 2 and Flood Zone 3. Where your address falls changes what the application has to deal with.

Which plan your extension is judged against

The adopted development plan covering Leatherhead is the Mole Valley Local Plan 2020 to 2039, adopted on 15 October 2024. Leatherhead has no neighbourhood plan and no designated neighbourhood area, so that Local Plan is the only district development plan document that applies. Neighbouring Ashtead and Bookham are in a different position, having both had their neighbourhood plans made in May 2017.

We are a contractor, not a planning agent. What that means in practice is that we build what has been approved, and we say so when a proposal looks like one that needs an application before it needs a builder. Most single storey rear extensions we are asked about here are kitchen extensions, where the new room joins the existing kitchen through an opening in the old rear wall. That opening needs its own steel, sized by the engineer, and it is seen at the structural elements inspection before it is boxed in. A two storey or multi storey extension adds rooms above and usually needs planning permission from Mole Valley District Council.

The inspections an extension triggers

The Southern Building Control Partnership lists an excavations inspection, to confirm foundations have been dug to a satisfactory depth. On ground that changes from chalk to London Clay to river terrace sand and gravel within one town, that is the stage which catches a foundation designed for the wrong material. We book it, and nothing is poured until it has happened.

The partnership is a shared service covering three council areas: Mole Valley, Reigate and Banstead, and Tandridge. Your application and your inspections go there rather than to Mole Valley District Council. We make the application and coordinate the visits, so there is one point of contact.

Kitchen extensions in Leatherhead

62% of the houses in Leatherhead 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 Leatherhead; the build figures are in the table above.

Side return extensions in Leatherhead

Side returns belong to Victorian and Edwardian terraces, and only 14% of homes in Leatherhead 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 Leatherhead

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 Leatherhead often needs planning permission from Mole Valley District Council. With 35% 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.

• Building control inspections at foundation, damp course and steel stages
• Single and double storey extensions
• First fix and second fix plumbing and electrics throughout

VOA Council Tax stock of properties, March 2025, for Leatherhead North and Leatherhead South & Ashtead South. Counts rounded by the VOA.

Once you know the scope of the house extensions in Leatherhead, it helps to read RSJ and steel beam installation in Leatherhead, house extensions in Epsom, basement extensions, the Party Wall Act process for extensions, house extensions across London and Side Return vs Rear Extension.

Trusted House Extensions in Leatherhead

An extension in Leatherhead is decided at the bottom before it is decided anywhere else. The ground changes from chalk to London Clay to river terrace sand and gravel inside the town, so the foundation is designed for the address rather than for the size of the room. We build to the structural engineer's calculations, book the excavations inspection before anything is poured, and coordinate the building control application throughout. We are fully insured and quotations are free and carry no obligation.

• Insulation and thermal detailing to current regulations
• Permitted development checked before you pay for a planning application
• Photographs kept at each stage for your records

Checked by Abdelaaziz Saaid, founder and director of GS Renovation Ltd (Companies House no. 14611254). Structural design is by the consulting engineer appointed to your project.