Is 3 m² measured inside or outside?

Externally — including the walls. A porch that feels 3 m² inside is usually over the limit.

Can I build a porch in a conservation area?

Yes. Class D has no extra restrictions on Article 2(3) land, so the same limits apply — unless an Article 4 direction has removed the right, which is common for front elevations in conservation areas.

Porch without planning permission

Porcheswithout planning permission

The short answer

Yes, within limits. A porch on any external door can be built without applying if its ground floor area is no more than 3 m², it's no higher than 3 m, and no part is within 2 m of a boundary with a road. This applies in conservation areas too.

Updated Sep 2026Rules: GPDO 2015, Schedule 2, Part 1, Class DEngland only

The limits

Limit	Standard	Conservation area
Floor area (external)	3 m²	3 m²
Height	3 m	3 m
Distance from road boundary	2 m	2 m
Flat or maisonette	Not permitted	Not permitted

Other conditions

Ground floor area no more than 3 m², measured externally.
No part higher than 3 m above ground level.
No part within 2 m of a boundary with a road or footpath.
Can be on any external door, not just the front.

When you can’t use permitted development

Flats & maisonettes
No householder permitted development rights at all.
Listed buildings
Listed building consent is needed for almost any change.
Conservation areas
Same limits as anywhere else.
Article 4 directions
Your council may have removed this right on your street.
Planning conditions
An old permission may have removed permitted development rights. Not published anywhere.
New builds
Often have permitted development removed by condition. Check your deeds.

Your exact limits

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Porch rules by council

Some councils have Article 4 directions that change these limits. Pick yours to see what applies locally.

Buckinghamshire Cornwall Wiltshire Birmingham Leeds Manchester Bristol Barnet Camden Westminster Brighton and Hove York All 308 councils →

Common questions

Is 3 m² measured inside or outside?: Externally — including the walls. A porch that feels 3 m² inside is usually over the limit.
Can I build a porch in a conservation area?: Yes. Class D has no extra restrictions on Article 2(3) land, so the same limits apply — unless an Article 4 direction has removed the right, which is common for front elevations in conservation areas.