House extensions in Sussex
Compare up to 3 free quotes from checked local builders for every type of house extension across Sussex.
Extending your home lets you create the space you need without the cost and upheaval of moving. Whether you want a bigger kitchen, an extra bedroom or a home office, you can fill in one short form or call 01273 115520, and up to 3 checked local builders will be in touch to arrange a visit and a quote. The service is free and there is no obligation. If you would rather not extend the footprint, a loft conversion or garage conversion may give you the extra room you need.
Types of extensions we cover
Single storey rear extensions
The most common type, extending into the garden to create a larger kitchen, dining or living space.
Two storey extensions
Adds space on two floors, often a bedroom or bathroom above a larger ground floor room.
Side return extensions
Well suited to Victorian and Edwardian terraces, using the narrow strip beside the back addition to widen the kitchen.
Wraparound extensions
Combines a rear and a side extension in one L-shaped addition for the largest gain in ground floor space.
Kitchen extensions
Creates an open-plan kitchen and dining area, often with roof lights or glazed doors onto the garden.
Extension prices
Extension costs depend on size, specification, ground conditions and access, and published guides vary. No source we use gives prices for Sussex specifically, so the table below shows national and South East figures from named cost guides. Less.co.uk's per m² figures exclude VAT, professional fees and interior fit-out. Less's figures put double storey extensions lower per square metre than single storey, since the foundations and roof are shared across two floors of new space.
| Extension | Price | Source |
|---|---|---|
| Single storey, national headline | £1,500 to £2,500 per m² | Less.co.uk |
| Single storey, South East, mid range | £1,900 to £2,900 per m² | Less.co.uk |
| Double storey | £1,200 to £2,000 per m² | Less.co.uk |
| Single storey, standard quality | £2,200 to £2,500 per m², excluding VAT | Homebuilding and Renovating |
| Single storey, 20m² | £20,000 to £44,000, average £30,000 | MyJobQuote |
| Two storey, average | £60,000 | MyJobQuote |
The only way to get an accurate price is to have builders visit, understand what you want and give you detailed written quotes. For a rough figure first, try our extension cost calculator, or read the single storey extension cost guide and two storey extension cost guide.
House extensions across Sussex: what you need to know
House extensions are one of the most popular building projects across Sussex, and it is easy to see why. Extending avoids the cost and disruption of moving, lets you stay in an area you know and gives you a layout planned around how you live. The right type of extension depends on the shape of your house, the size of the garden and how much of the existing building you are willing to open up.
Budget for more than the build itself. Less.co.uk lists professional fees at £3,000 to £10,000, bi-fold doors at £3,000 to £6,000 and a roof lantern at £1,500 to £3,500, and adds that difficult ground can add £2,000 to £8,000. Its figures exclude VAT, so ask every builder to show VAT clearly on the quote. A contingency for unexpected work is sensible on any project, particularly on older houses.
Many extensions can be built under permitted development. The Planning Portal says a single storey rear extension must not extend more than three metres beyond the original rear wall, or four metres for a detached house, and must not be more than four metres high. These rights apply to houses only, not to flats or maisonettes. In conservation areas, side extensions and rear extensions of more than one storey need householder planning permission, and listed buildings need listed building consent for work that affects their character.
Where you do need a planning application, GOV.UK sets the householder fee in England at £548 from 1 April 2026. Permission is never guaranteed, so check with your local planning authority and building control before you commit, and read our extension planning permission guide for the main limits.
Frequently asked questions
How much does an extension cost per m²?+
Less.co.uk's 2026 guide gives a national headline of £1,500 to £2,500 per m² for a single storey extension and £1,900 to £2,900 per m² for a mid range one in the South East. Its figures exclude VAT, professional fees and interior fit-out, and it puts double storey extensions at £1,200 to £2,000 per m².
How much does a single storey extension cost in total?+
MyJobQuote puts a 20m² single storey extension at £20,000 to £44,000, with an average of £30,000. Its 2026 double storey guide gives an average of £60,000 for a two storey extension.
What extra costs should I budget for?+
Less.co.uk lists professional fees at £3,000 to £10,000, bi-fold doors at £3,000 to £6,000 and a roof lantern at £1,500 to £3,500, and says difficult ground can add £2,000 to £8,000. A contingency for unexpected work is sensible, particularly on older houses.
Do I need planning permission for a rear extension?+
Not always. The Planning Portal says a single storey rear extension under permitted development must not extend more than three metres beyond the original rear wall, or four metres for a detached house, and must not be more than four metres high. These rights apply to houses only, not to flats or maisonettes, and are more limited in conservation areas.
How much is a householder planning application?+
GOV.UK sets the householder planning application fee in England at £548 from 1 April 2026. Permission is never guaranteed, so check with your local planning authority before you commit.
Sources for the prices on this page
- Less.co.uk: House extension cost per m² in 2026, checked October 2026
- Homebuilding and Renovating: How much does an extension cost in 2026?, checked October 2026
- MyJobQuote: How much does a single storey extension cost in the UK?, checked October 2026
- MyJobQuote: Double storey extension cost guide (UK prices 2026), checked October 2026
- GOV.UK: Fees for planning applications in England from 1 April 2026, checked October 2026
Get your free extension quotes now
Fill in the form or call 01273 115520, and up to 3 checked local builders will be in touch.