House Extensions Chesham

GS Renovation builds house extensions in Chesham, from single-storey rear and kitchen extensions on the town's semis, terraces and bungalows to side and double-storey extensions where the plot allows. A home extension here now has a written design code to satisfy as well as the building regulations. We handle the build: foundations, structure, roof, envelope, and the building control application and inspections. We appoint a structural engineer for the steelwork and build to their calculations, and we never produce those calculations ourselves. This page covers the local planning framework, the material and roof rules, the ground and radon position, and the inspection programme.

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

Chesham now has its own neighbourhood plan and design code

The Chesham Neighbourhood Plan 2024 to 2040 was approved at a referendum on 6 November 2025, with 89 per cent of votes cast in favour of Buckinghamshire Council using it to decide planning applications in the parish. Policy CHESH4 requires development proposals in the defined Chesham Design Code Area to respond positively to the relevant development and design principles in the Chesham Design Code. The code applies mainly to the Tightly Formed Centre, Town Centre Fringes and Suburban Roads design character areas, and does not cover the modern outer suburbs of the town.

Two wider constraints sit around all of it. Growth around Chesham was restricted by the designation of the Metropolitan Green Belt in 1958, and restricted again by its extension in 1972. Buckinghamshire Council's published list of current Article 4 Directions covers nine locations across the county, and none of them is in Chesham, though the list can change and is checked again before an application. A single-storey rear extension within the national limits can often be built under permitted development, including inside the conservation area; a side or two-storey extension in the conservation area, any extension to a listed building, and anything beyond the limits needs planning permission from Buckinghamshire Council.

Housing in Chesham

Around 9,950 homes make up Chesham on the valuation list; 25% are flats and 75% houses, and 17% date from before 1919, 12% from between the wars and 71% from after 1945. 31% of homes here are terraced; a rear extension on a terrace in Chesham digs foundations close to both neighbours, so notices to both are normal.

The design code names the materials a street facing elevation may use

The Chesham Design Code states that only brick, timber, flint, painted brick or painted render will be permitted for street facing facades. It allows systems that accurately mimic them, such as mathematical tiles or brick slips. It also requires all bricks on building facades or street facing elevations to be moulded or stock bricks, and states that wire cut or extruded bricks must not be used where they are visible.

Roofs are covered as well. The code requires roof tiles to be plain clay tiles or slate tiles, and states that pan tiles, concrete tiles and plastic tiles must not be used. It gives the historic roof pitch used in Chesham and the Chilterns as either 42.5 degrees or 47.5 degrees, and says new roof pitches should never be lower than 40 degrees. That floor of 40 degrees sets your ridge height, which belongs on the drawing rather than on site.

Foundations and radon both depend on where in the town you are

The British Geological Survey maps the bedrock beneath Chesham town centre and the floor of the Chess valley as the New Pit Chalk Formation. It describes that formation as principally blocky, white, firm to moderately hard chalk with numerous marls or paired marl seams. On the plateau ground above the town at Botley, Chartridge Lane and Asheridge, the mapped superficial deposit is the Clay-with-flints Formation. The survey describes that as unbedded and heterogeneous, dominated by orange brown and red brown sandy clay with abundant nodules and rounded pebbles of flint.

Radon varies across the town too. The BGS Radon Indicative Atlas gives a maximum radon potential of 5 to 10 per cent for the one kilometre squares covering northern and north western Chesham. It gives 1 to 3 per cent for the squares covering the south and east of the town. UKHSA states that when extensions are made to existing buildings in high radon areas, the Building Regulations require protective measures against radon entering the building.

Buckinghamshire Council's own building control service inspects the work

Buckinghamshire Council runs its own building control service, and site inspections in Chesham are booked through the former Chiltern and South Bucks district area booking form. The council states that a house extension normally requires five building control inspections, and that the number is usually agreed before work begins. It names foundations, damp proofing, roof structure and drainage as intermediate stages, alongside the completion inspection.

Those stages are the spine of the programme. We make the application, agree the inspection stages with the council before work starts, and book each visit so the trench, the membrane, the roof structure and the drains are all seen open. Covering work before it has been inspected is the expensive mistake on an extension.

Kitchen extensions in Chesham

44% of the houses in Chesham 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 Chesham; the build figures are in the table above.

Side return extensions in Chesham

Side returns belong to Victorian and Edwardian terraces, and only 17% of homes in Chesham 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 Chesham

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 Chesham often needs planning permission from Buckinghamshire Council. With 33% 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.

• Roof works and structural alterations at roof level
• Levels, drainage and landscaping made good around the new build
• Full fit-out, finishing and making good

VOA Council Tax stock of properties, March 2025, for Chesham West, Chesham East and Chesham South. Counts rounded by the VOA.

Before committing to house extensions in Chesham, it is worth looking at RSJ and steel beam installation in Chesham, house extensions in Amersham, basement extensions, the Party Wall Act process for extensions, house extensions across London and Party Wall Act Explained.

The GS Renovation Difference in Chesham

An extension in Chesham is now judged against design rules written down locally rather than left to officer judgement. That helps if you read them early, because the code decides what a street facing elevation can be built and roofed in, and those are drawing decisions rather than first fix decisions. We coordinate the building control application and the inspections, agree the stages with the council before work starts, and appoint the structural engineer for any steelwork. We never produce structural calculations ourselves. GS Renovation Ltd is fully insured, registered in England, company number 14611254, and quotations are free and without obligation.

• Aftercare and snagging support once the job is finished
• Building control inspected at foundation, damp course and steel stages
• Insulation and thermal detailing to current regulations

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.