Do I Need Planning Permission for an Extension? (UK, 2026)
31 Oct 2026Good news first: a large share of UK home extensions never need a full planning application. They're covered by Permitted Development (PD) rights — a set of pre-approved limits you can build within. But PD has real conditions, and even when you don't need planning permission, you almost always still need Building Regulations approval. Here's how to tell what applies to you.
When you probably DON'T need full planning permission
A single-storey rear extension often falls under Permitted Development if it stays within limits such as:
- It doesn't extend beyond the rear wall by more than 4 m (detached) or 3 m (semi/terraced) — larger projections up to 8 m / 6 m may be allowed under the "prior approval" neighbour-consultation route.
- It's no higher than 4 m and doesn't go above the existing roofline.
- It covers no more than half the land around the original house.
- Materials are similar in appearance to the existing house.
- It's not in front of the principal elevation (i.e. not sticking out the front).
When you almost certainly DO need planning permission
- You live in a flat or maisonette — PD rights for extensions generally don't apply.
- Your home is listed, or in a conservation area, National Park or AONB — tighter rules, often no PD.
- It's a double-storey extension beyond modest limits, or any front extension.
- Your PD rights have been removed (common on newer estates — check your deeds or a previous planning condition).
What you still need even under Permitted Development
PD only removes the planning application. These still apply:
- Building Regulations. Structure, insulation, drainage, fire safety and electrics all have to be signed off. This is non-negotiable and separate from planning.
- Party Wall Act. If you build on or near a shared boundary, you must serve notice on the neighbour — ideally months ahead.
- A Lawful Development Certificate (optional but wise). For about £129 it gives you official proof the work was permitted — invaluable when you sell.
The 2026 fees
- Householder planning application (England): £258
- Lawful Development Certificate: £129
- Building Regs application & inspections: £500–£1,000+
Fees differ in Scotland, Wales and Northern Ireland — check your local authority's planning portal.
Don't guess — it's the cheapest step to get right
Building something that turns out to breach PD limits is the most expensive mistake in home improvement: you can be forced to alter or remove it, and it will block a sale. A good architect or builder will tell you exactly which route applies before a spade goes in the ground. When you post your job, ask bidders to confirm the planning route in their quote.
Get competing quotes for your extension — free
Post your job once on BidsAndMore and vetted local builders bid for it. You compare prices side by side and pick the one that's right — most homeowners find that competition alone knocks thousands off the first number they were quoted.
Post your extension job →FAQ
Can I start building before approval?
No. Even under Permitted Development you need Building Regulations, and for a full application you must wait for the decision. Starting early risks an enforcement notice.
How long does planning permission take?
A householder application usually takes around 8 weeks in England once validated. Permitted Development with prior approval is faster.
Related: House extension cost guide · Single vs double-storey · Why unqualified work can void a claim