Home extensions in Blackheath
More space without moving: we plan and build extensions across Blackheath, with one team for the drawings, the council and the build.
- Postcode districtsSE3, SE4, SE7, SE10, SE12, SE13
- Price regionLondon (×1.3)
- Planning rulesEngland
- Site visitFree, no obligation
Covering Blackheath and nearby
We cover Blackheath and the postcode districts SE3, SE4, SE7, SE10, SE12, SE13. We also work in nearby Greenwich (1 mile), Catford (2 miles), Brockley (2 miles), New Cross (2 miles), Eltham (2 miles). Swanley, in Kent, is roughly 9 miles from Blackheath and also on our list.
Approvals for an extension in Blackheath
In England a single-storey rear extension can usually go up to 3 m beyond the original rear wall of a semi-detached or terraced house, or 4 m on a detached house, without a planning application, provided it is no more than 4 m high, keeps eaves to 3 m within 2 m of a boundary and, with other buildings, covers no more than half the land around the original house. The larger home extension prior approval scheme raises those depths to 6 m and 8 m, with neighbours notified and a 42-day decision.
In England a two-storey rear extension is permitted development only if it projects no more than 3 m from the original rear wall, sits at least 7 m from the rear boundary, matches the roof pitch and uses obscure, non-opening side windows upstairs. Most two-storey extensions therefore go through a householder planning application, which costs £548 from 1 April 2026 and normally takes about 8 weeks.
In a conservation area, national park, National Landscape, the Broads or a World Heritage Site the permitted development limits are tighter (no side or two-storey extensions without an application). Listed homes need listed building consent, and if permitted development rights have been removed, any extension needs an application.
If the work involves a shared wall, building on the boundary, or digging foundations within 3 m (sometimes 6 m) of a neighbour's building, the Party Wall etc. Act 1996 applies and notice must be served before work starts: two months for work to a party wall, one month for new walls on the boundary and for excavations.
Applications are decided by the local planning authority (your district, borough or unitary council).
Popular extension prices in Blackheath
We publish guide prices so you can budget before anyone visits. For Blackheath they are adjusted by ×1.3, the factor we use across London.
| Extension type | Example size | Standard spec (inc VAT) |
|---|---|---|
| Extensions over a garage | 12 m² | £32,500 – £42,500 |
| Kitchen extensions | 20 m² | £54,500 – £69,000 |
| Wraparound extensions | 25 m² | £74,500 – £94,500 |
| Single-storey rear extensions | 20 m² | £53,000 – £68,000 |
| Double-storey extensions | 32 m² | £74,500 – £98,000 |
| Side return extensions | 11 m² | £34,000 – £43,000 |
What works best for Blackheath houses?
In London, space is at a premium and gardens are often short, so side returns, wraparounds and carefully planned rear extensions tend to make the most of every metre.
Start by comparing side return extensions, glass box extensions and wraparound extensions: between them they cover most of the layouts we see requested for houses like these.
Every extension type in Blackheath
- Conservatory replacement extensions · from £26,000
- Bungalow extensions · from £34,000
- Planning permission for extensions · from £450
- Extensions over a garage · from £31,000
- Annexe extensions · from £71,500
- Utility and boot room extensions · from £18,000
- Building regulations for extensions · from £1,150
- Single-storey rear extensions · from £27,000
- Flat roof extensions · from £27,000
- Double-storey extensions · from £49,000
- Home office extensions · from £20,500
- Side return extensions · from £23,000
- Glass box extensions · from £39,000
- Timber frame extensions · from £27,000
- Extension plans and drawings · from £1,550
- Pitched roof extensions · from £28,500
- Bedroom extensions · from £33,500
- Porch extensions · from £5,200
- Side extensions · from £28,500
- Kitchen extensions · from £35,000
- Wraparound extensions · from £46,500
- Orangery extensions · from £39,000
Free site visit
We visit your Blackheath home, measure up, talk through what you want and check the planning position.
Design and approvals
We produce the drawings and structural design, and manage the approvals so they are in place before work starts.
Fixed written price
We confirm the build price in writing, based on the approved drawings and the finishes you have chosen.
Build and sign-off
Our team builds the extension, keeps you updated weekly and finishes with building control sign-off.
Questions about extensions in Blackheath
How much does an extension cost in Blackheath?
Using our London factor (×1.3), a standard-spec single-storey extension of 20 m² is a guide £53,000 to £68,000 including VAT, and a 32 m² two-storey extension £74,500 to £98,000. Your written price follows the survey.
Who do I contract with?
Your contract is with S&K Property Investments and Improvement Ltd, which designs and manages the project and the build teams who carry it out.
Do I need planning permission for an extension in Blackheath?
Not always. It depends on the size, position and your property's history. Many single-storey rear extensions in England are permitted development or can use prior approval.
Do you cover all of Blackheath?
Yes, including the surrounding parts of Greater London. Site visits are free and there is no obligation.
Will my neighbours need to be told?
If you apply for planning or prior approval the council notifies them, and in England party wall notices may be needed for work near a shared boundary.
Book a free site visit in Blackheath
We will measure up, check the planning position and give you honest guide figures.
- Free, no-obligation site visit
- Planning route checked before you spend on drawings
- Written price once the design is agreed
- Building control sign-off at the end
Prefer to talk? Call 0800 088 6341 or .
Book a free site visit
Tell us a little about the project and we will arrange a time.