Bungalow and upward extensions: Costs & Planning

What is an upward extension?

An upward extension adds a new storey on top of an existing house, most often turning a bungalow into a two-storey or chalet-style home. It can double the floor area without using any of the garden.

Detached bungalow converted to a chalet-style house with front dormers and a raised roof

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.

Typical time on site: 12 to 24 weeks
Guide price: £2,200 to £3,800 per m² of new floor
Building regulations: Required

What is included?

Structural survey of walls and foundations
Design and planning or prior approval application
Roof removal and temporary weather protection
New first-floor structure, walls and roof
Staircase and changes to the ground floor layout
Full fit-out of the new rooms

How much does an upward extension cost?

Adding a full 60 m² first floor to a bungalow typically costs around £170,000 to £200,000 including VAT at a good specification.

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

Unit: per m² of new floor area. Guide ranges only; your price is fixed in writing after the survey.

Use the guide price tool for a figure based on your size and specification, or see all guide prices.

Does an upward extension need planning permission?

England

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.

Wales

Adding a storey in Wales needs planning permission. We prepare the application with drawings showing how the new roofline fits the street.

Scotland

Adding a storey in Scotland needs planning permission and a building warrant.

Northern Ireland

Adding a storey in Northern Ireland needs planning permission and building control approval.

What about building regulations?

Full building regulations approval, with structural calculations proving the existing walls and foundations can take the new load.

What should I think about before starting?

Some bungalow foundations need strengthening before a storey can be added.
The staircase takes space from the ground floor plan.
The house is exposed while the roof is off, so the sequence is planned tightly.
Neighbours’ light and privacy are the main planning tests.

How does the project run?

Tell us about the project. Call, use the guide price tool or send the form with a few photos and a postcode.
Free site visit. We measure up, look at access, drains and the structure, and talk through options and budget.
Design and fixed price. You get drawings and a written price for the agreed specification before anything is ordered.
Build and hand over. Our teams build to the programme, building control inspects, and you get the completion paperwork at the end.

Questions about bungalow and upward extensions

Can I add a first floor to my bungalow?

Often yes, if the walls and foundations can carry the load and planning allows. We check the structure first.

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.

Is an upward extension permitted development?

In England, Class AA allows it on many post-1948 houses through a prior approval application. Elsewhere planning permission is needed.

Do we need to move out?

Often for part of the job, while the roof is off and the new floor is formed. We plan this with you.

How long does it take?

About 12 to 24 weeks on site.

Related projects

Where do we build bungalow and upward extensions?

We take on bungalow and upward extensions across England, Wales, mainland Scotland and Northern Ireland. Choose your area: