Do I Need Planning Permission for a Two-Storey Rear Extension? (2026 UK)
In most cases, yes — a two-storey rear extension usually needs a full planning application in 2026. But not always: a modest two-storey rear extension can fall under Permitted Development (PD) if it projects no more than 3m from the original rear wall, keeps at least 7m between the new rear wall and the rear boundary, matches the existing roof pitch, and uses similar materials. Cross any of those lines — and most real-world schemes do — and you need full planning permission (£258 householder fee in England for 2026).
Two-storey rear extension — the short answer
- Usually needs full planning permission — most two-storey rear extensions exceed PD limits.
- PD is possible if projection ≤ 3m, ≥ 7m from rear boundary, matching pitch & materials.
- No PD at all in conservation areas, on flats/maisonettes, or where Article 4 applies.
- Householder application fee: £258 (England, 2026); decision in ~8 weeks.
- Always need Building Regulations regardless of the planning route.
Even when PD technically applies, a Lawful Development Certificate (£129) is strongly advised — it is your legal proof the works were permitted, and buyers’ solicitors routinely ask for it. The 7m-to-rear-boundary rule is what catches most two-storey schemes, because typical UK back gardens simply aren’t deep enough.
Permitted Development Limits for Two-Storey Rear Extensions
For a detached, semi-detached or terraced house (not a flat), a two-storey rear extension may be PD only if ALL of these hold:
PD rights do not exist for flats, maisonettes, listed buildings, or in many conservation areas / Article 4 zones. Always confirm with your local planning authority before relying on PD.
When Full Planning Permission Is Unavoidable
Projection over 3m
Almost every kitchen-diner two-storey scheme projects further than 3m, immediately requiring full planning.
Shallow rear garden
If you can’t keep 7m to the rear boundary, PD is off the table — the usual blocker on UK terraces.
Conservation area / Article 4
PD rights are commonly removed; even minor works need consent. Check your address on the council map.
Flats & maisonettes
No householder PD rights apply at all — a full application is always required.
Common Questions
Related Guides
More planning, cost and how-to guides for your extension project.
Get 3 Free Extension Quotes
BestBuilders matches you with 3 vetted extension builders who can advise on the planning route and price your two-storey rear extension against one brief. FMB / CIOB members, 10-year insurance-backed warranty.