House Extensions Coulsdon

GS Renovation builds house extensions throughout Coulsdon, where the 1930s semis, post-war detached houses and bungalows tend to sit on generous plots with room to grow. We handle everything from foundations to the final fit-out under one accountable team.

In Coulsdon, 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 Coulsdon: the structural engineer we appoint designs the structure, we build it, and building control signs it off.

Rear and side return extensions in Coulsdon

The wide plots common in Coulsdon suit rear kitchen extensions that stretch into the garden and side extensions that use the space beside the semi. A single storey rear extension typically opens the kitchen into a large kitchen-diner, which usually calls for a steel beam across the old rear wall, while a wrap-around design combines the rear and the side return into one broad living space.

We start with the groundworks, digging and pouring foundations to a depth agreed with building control for the ground conditions on your plot. Steel beams carry the openings, the roof is tied into the existing structure, and we complete the fit-out including plastering, electrics, plumbing, heating and decoration. You deal with one team from the first trench to the final coat of paint.

Housing in Coulsdon

For Coulsdon the Council Tax list gives about 7,540 homes; by type 27% flats and 73% houses, by age 62% post-war, 30% interwar and 8% older than 1919. A rear extension on a semi in Coulsdon digs beside the attached neighbour, so one party wall notice is usual, and 26% of homes here are semi-detached.

Sewers, trees and conservation rules behind a Coulsdon extension

Croydon says a building notice can be used when building an extension, but a full plans application must be submitted if the work involves building over or within 3 metres of a public sewer. Behind a Coulsdon semi the drain from your house may join the one from next door, and a drain shared by more than one property is normally a public sewer even where it crosses your garden. Before choosing the route we have the drains traced and, where the line is unclear, surveyed by camera. If a sewer lies inside that distance, the drawings, the foundation design and the sewerage company's build over agreement all move earlier in the programme.

In Old Coulsdon, the Bradmore Green Conservation Area was designated July 1968. In a Croydon conservation area planning permission is required for side extensions and some rear extensions, and Croydon's conservation guidance SPD says two storey rear extensions are generally unlikely to be considered acceptable. Trees add a second clock. Croydon requires at least 6 weeks' notice to the council before works to any tree in a conservation area, and cutting back roots for a trench can count as works to the tree. On a Coulsdon plot inside the conservation area, that notice goes in with the design, not with the digging.

Planning and permitted development in Coulsdon

A single storey rear extension is permitted development on many Coulsdon houses: up to three metres deep on a semi and four on a detached house, no more than four metres high, with eaves no higher than three metres within two metres of a boundary and no more than half the original garden covered. The larger home extension route doubles those depths, subject to prior approval from Croydon Council and a neighbour consultation. A single storey side extension can also qualify if it is no wider than half the original house. Two-storey extensions usually need a planning application, a conservation area removes permitted development for side and two-storey extensions, and flats have none at all. We check your address, its planning history and any Article 4 direction before design, so you know which route applies before you commit.

Separate from planning, every extension must meet building regulations for its foundations, structure, insulation, drainage and fire safety, inspected as the work proceeds. Where the new build sits against the party wall shared with a neighbouring semi, the Party Wall etc. Act 1996 also applies, so you serve the necessary notices as building owner. We keep planning, building control and the programme around your notices running in step.

Kitchen extensions in Coulsdon

66% of the houses in Coulsdon 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 Coulsdon; the build figures are in the table above.

Double storey extensions in Coulsdon

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 Coulsdon often needs planning permission from Croydon Council. With 48% of homes here semi-detached or detached, the side of the house is often an option too. Bradmore Green Conservation Area, designated July 1968, is the heart of Old Coulsdon around Bradmore Green and Grange Park (council source). Our double storey extension page explains the build, at £1,800 to £2,600 per m² across both floors.

• Roof works and structural alterations at roof level
• Levels, drainage and landscaping made good around the new build
• Planning applications and permitted development assessments

VOA Council Tax stock of properties, March 2025, for Coulsdon and Old Coulsdon. Counts rounded by the VOA.

Work in Coulsdon rarely sits on its own, so you may also want RSJ and steel beam installation in Coulsdon, house extensions across Croydon, basement extensions, a garage conversion instead, house extensions across London and Side Return vs Rear Extension.

The GS Renovation Difference in Coulsdon

GS Renovation gives Coulsdon homeowners a single point of responsibility for the whole extension, from checking whether you need planning permission to pouring foundations, setting steel and finishing the interior. Our founder's 30+ years of building means we know the 1930s and post-war stock, the generous plots and Croydon Council's requirements, so the project runs to plan.

• Building control applications and inspections coordinated for you
• Foundation depth set after trial holes, drains and trees are checked
• Building control inspected at foundation, damp course and steel stages

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.