Double-storey extensions in Southampton

Covering Southampton

Alongside Southampton, we also cover Totton (4 miles to the west), Eastleigh and Fareham.

Homes in the South East

Many South East homes are inter-war or post-war semis and detached houses with room for rear and side extensions, while historic town centres and villages bring conservation area and listed building controls.

What does a double-storey extension involve?

A double-storey extension adds new rooms on both the ground and first floor in one build, typically a larger kitchen or living space downstairs and an extra bedroom or bathroom above. Because the roof and foundations are shared, the cost per square metre is usually lower than a single-storey extension.

Householder planning application
Foundations, steelwork, brick and block walls, roof
Joining the new first floor to the existing landing

What is the guide price for a double-storey extension in Southampton?

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

Double-storey extensions	Guide price incl. VAT
Standard specification	£2,400 to £2,900 per m²
Good specification	£2,900 to £3,400 per m²
High specification	£3,400 to £3,850 per m²

Planning and building rules in Southampton

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.

Two-storey rear extensions can sometimes be permitted development in England (no more than 3 m deep, at least 7 m from the rear boundary, roof pitch to match), but most two-storey and all two-storey side extensions need householder planning permission. Expect around eight weeks for a decision once the application is validated.

What should I think about before starting?

Neighbours’ light is assessed using the 45-degree guide many councils use.
The new roof is tied into the old one, so roof tiles and ridge details need to match.

How does the project run?

Send us the details. Give us a postcode, a rough idea of size and some photos, by phone, form or the guide price tool.
We visit and measure. A surveyor checks the house, the boundaries and the ground, and discusses what is realistic.
Drawings, approvals, written quote. We prepare the design, apply for the approvals it needs, and give you a fixed price in writing.
We build it. Work follows an agreed programme, with inspections at each stage and a final sign-off.

Questions about a double-storey extension in Southampton

Does a two-storey extension need planning permission?

Usually yes. In England some two-storey rear extensions are permitted development, but side extensions over one storey always need planning permission.

Will we need to move out?

Most people stay. The noisiest stage is when we break through into the existing first floor, which we plan for a short window.

Can you visit a house in Southampton to quote?

Yes. After a short call we arrange a site visit to measure up and agree what the design needs to do, then send a written price.

Double-storey extensions near Southampton

Learn more about double-storey extensions, or see every project we cover in Southampton.