House Extensions Beaconsfield

An extension is a foundation, a structure, a roof and a set of approvals, and the approvals decide the shape before the builder does. We coordinate the drawings, appoint the structural engineer, make the building control application, book the inspections and build the thing. We never produce the structural calculations ourselves. This page sets out the Beaconsfield policy and ground conditions worth knowing before anything is drawn.

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

Local policy fixes how close to the boundary a first floor can sit

Policy H11 of the South Bucks District Local Plan requires an extension of more than one storey, or any extension at or above first floor level, to sit at least one metre from either flank boundary of the site. The plan's House Extensions Design Guide goes further on roofs. Where the original building has a pitched roof, it says a two storey extension should also have a pitched roof at the same or a close angle. It adds that flat roofs for two storey extensions will usually be unacceptable.

That plan is not new. The South Bucks District Local Plan was formally adopted on 22 March 1999, and Buckinghamshire Council still lists it among the local plans for the former South Bucks district area. The South Bucks Core Strategy was adopted in February 2011 and sits alongside it. Both apply to your extension until they are replaced.

Housing in Beaconsfield

The Council Tax list puts Beaconsfield at about 5,390 homes, 23% flats against 77% houses; 10% went up before 1919, 15% between the wars and 76% after 1945. A detached house in Beaconsfield often extends far enough from the boundary that no party wall notice is needed, and 42% of homes here are detached.

Two parts of Beaconsfield are Residential Areas of Exceptional Character

The South Bucks District Local Plan defines two of them in the town: Penn Road, and a large area based around Burkes Road and Gregories Road. The plan describes both as 1930s suburban development with plot sizes in excess of about 2,500 square metres, frontages of about 25 metres and spacing between houses of about 10 metres.

Policy H10 refuses house extensions in such an area where they would harm that character, and warns that greater gaps to the boundary than one metre may be required there. The boundary drawn was deliberate: the plan records that the area between Gregories Road, Furzefield Road and Burkes Road was left outside it, as was the southern part of Burgess Wood Road South. Whether you sit inside or outside changes the brief.

The ground under a Beaconsfield extension is not one thing

The superficial deposit mapped across much of built-up Beaconsfield is the Beaconsfield Gravel Member, a sand and gravel unit named after the town. The British Geological Survey describes it as 1 to 7 metres of variably sandy and clayey gravel, and gives its type section as terrace and borehole data at Beaconsfield Station, where 6 metres of gravel overlie the Chalk. A range of 1 to 7 metres is not a foundation depth.

Buckinghamshire Council's appraisal states that the underlying geology is chalk with mainly gravelly loam soil, and adds that with pockets of clay in the area residents report soil can vary from one garden to the next. At Hampden Hill the mapping shows chalk bedrock with no superficial deposit over it, and the appraisal records an old chalk pit in the gardens of numbers 4 and 6. That is an argument for a trial hole rather than an assumed depth.

Buckinghamshire Council expects five inspections on a house extension

The council states that a house extension normally requires 5 building control inspections, and that the number is usually agreed before work begins. It names foundations, damp proofing, roof structure and drainage among the intermediate stages its inspector needs to see.

Those visits are fixed points in the programme, and each one has to happen before the next stage covers it up. We agree the schedule with building control at the start and plan the trades around it. That is why the sequence in our quotation reads the way it does, and why the foundation stage is not something to rush.

Kitchen extensions in Beaconsfield

79% of the houses in Beaconsfield 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 Beaconsfield; the build figures are in the table above.

Side return extensions in Beaconsfield

Side returns belong to Victorian and Edwardian terraces, and only 10% of homes in Beaconsfield 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 Beaconsfield

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 Beaconsfield often needs planning permission from Buckinghamshire Council. With 61% 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
• Trial holes to set foundation depth near drains and trees
• Bi-fold, sliding and French door openings to the garden

VOA Council Tax stock of properties, March 2025, for Beaconsfield Town. Counts rounded by the VOA.

If this is your first project in Beaconsfield, these are worth a look: RSJ and steel beam installation in Beaconsfield, house extensions in High Wycombe, side return infills, a garage conversion instead, house extensions across London and Garage Conversion Cost.

Why Beaconsfield Homeowners Choose GS Renovation

An extension in Beaconsfield is decided on the drawing board by planning policy and on site by ground conditions, and those two are settled before a price means anything. We coordinate the planning side, appoint the structural engineer, make the building control application to Buckinghamshire Council and fit the five inspections into the programme. Groundworks, structure, roof, services and finishes then run under one contractor to one written programme, so there is nobody to chase between trades. We build to the engineer's calculations and never produce them. GS Renovation Ltd is fully insured, registered in England, company number 14611254, and quotations are free and without obligation.

• Garden levels and access made good where the build meets outside
• Insulation and thermal detailing to current regulations
• Paperwork and certificates handed over for when you sell

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.