Bungalow and upward extensions in Isleworth

Covering Isleworth

Our coverage around Isleworth (TW7) also includes Hounslow, Heston and Richmond.

Homes in London

Terraced houses dominate many London neighbourhoods, so most projects involve shared walls, narrow access and a party wall process. Conservation areas are widespread, and some boroughs have their own mansard and basement guidance.

What does an upward extension involve?

The first question is whether the existing walls and foundations can carry the extra load, so we start with a structural survey. Then we design either a full first floor or a raised roof with dormers, handle planning or prior approval, and build the new storey while protecting the floor below.

Structural survey of walls and foundations
Staircase and changes to the ground floor layout
Full fit-out of the new rooms

What is the guide price for an upward extension in Isleworth?

Typical ranges for bungalow and upward extensions. Ground conditions, access and specification move the final figure, which we fix in writing before work starts.

Bungalow and upward extensions	Guide price incl. VAT
Chalet conversion with dormers (total)	£45,000 to £85,000
New first floor, standard specification	£2,200 to £2,800 per m²
New first floor, good specification	£2,800 to £3,300 per m²
New first floor, high specification	£3,300 to £3,800 per m²

What approvals does an upward extension need in England?

Projects in England go through two separate checks. Planning (or confirmation that the work is permitted development) comes from the district, borough or unitary council, and building regulations approval comes from the council’s building control team or a registered building control approver. Where work touches a shared wall or digs near a neighbour’s foundations, the Party Wall etc. Act 1996 applies.

In England, Class AA permitted development allows an extra storey on many detached and semi-detached houses built between July 1948 and October 2018, subject to a prior approval application covering design, neighbours’ amenity and other matters. Houses in conservation areas and other protected land need full planning permission, as do most chalet conversions with front dormers.

What should I think about before starting?

The house is exposed while the roof is off, so the sequence is planned tightly.
Neighbours’ light and privacy are the main planning tests.

From first call to completion

Tell us about the project. Call, use the guide price tool or send the form with a few photos and a postcode.
We visit and measure. A surveyor checks the house, the boundaries and the ground, and discusses what is realistic.
Price and paperwork. The design is priced line by line, and we submit the planning and building control applications.
Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.

Bungalow and upward extensions: common questions

How much does it cost to add a storey?

Around £2,200 to £3,800 per square metre of new floor including VAT, or £45,000 to £85,000 for a chalet conversion with dormers.

How long does it take?

About 12 to 24 weeks on site.

Who deals with the council for a project in Isleworth?

We do. We prepare the drawings, submit planning or permitted development paperwork if needed, and arrange building control inspections.

Bungalow and upward extensions in nearby towns

Learn more about bungalow and upward extensions, or see every project we cover in Isleworth.