Permitted Development | Capital Architecture

First: does your home have permitted development rights?

Permitted development rights don't apply, or are restricted, if:

You live in a flat or maisonette. There are no householder rights, so you'll need planning permission.
Your home was created by a change of use under permitted development, such as an office converted to flats
Your council has an Article 4 direction covering your street
An earlier planning permission removed the rights by condition. This is common on newer homes.
You're in a conservation area, National Park, Area of Outstanding Natural Beauty or World Heritage Site, where rights are reduced
Your home is listed. Listed building consent is needed for most changes.

Not sure? We'll check your property's history and constraints for free.

Rule	Detached house	Semi-detached or terraced
Maximum depth beyond the original rear wall	4m	3m
Maximum height	4m	4m
Eaves height within 2m of a boundary	3m max	3m max

Also:

Materials should look similar to the existing house
Extensions and outbuildings together can't cover more than half the garden around the original house
"Original house" means the house as first built, or as it stood on 1 July 1948. Earlier extensions count towards the limits.

You can build a single-storey rear extension up to 8m (detached) or 6m (other houses) deep, and up to 4m high, through prior approval.

How it works:

We submit details to the council (fee £249)
The council notifies your adjoining neighbours, who have at least 21 days to comment
If neighbours object, the council considers the impact on their amenity
If the council doesn't decide within 42 days, the extension is treated as approved

Not available in conservation areas or other protected areas.

Up to 3m beyond the original rear wall
At least 7m from the rear boundary
Roof pitch to match the existing house as far as practicable
Upper-floor side windows must be obscure-glazed, and non-opening below 1.7m above the floor
Not permitted in conservation areas and other protected areas

Rule	Limit
Additional roof volume, terraced house	40m³
Additional roof volume, semi-detached or detached	50m³
Height	No higher than the highest part of the existing roof
Front roof slope facing a road	No extension forward of it
Set back from the eaves	At least 0.2m, as far as practicable
Balconies, verandas, raised platforms	Not permitted
Side-facing windows	Obscure-glazed, and non-opening below 1.7m

Previous roof additions count towards the volume allowance. Roof extensions are not permitted development in conservation areas.

Illustration: a rear dormer on a terraced house with its volume worked out

Not in front of the house, and single storey only
Eaves up to 2.5m; overall height up to 4m with a dual-pitched roof, or 3m otherwise
Maximum 2.5m high if within 2m of a boundary
Must be used for purposes incidental to the house, such as a home office, gym or studio. Not a separate bedroom or home.
Counts towards the half-garden coverage limit
In protected areas: nothing to the side of the house, and extra limits further from it

A permitted development project doesn't legally need a certificate, but we almost always recommend one.

Certainty before you build: the council formally confirms your project is lawful
Selling your home: buyers' solicitors often ask for proof
Protection: if a neighbour complains, you have the paperwork
Cost: £274 for a proposed development certificate in England (from April 2026)

Permitted development is quicker and more certain, but it's a one-size-fits-all rulebook. A planning application can often get you:

We'll show you both options side by side before you decide.

Building regulations still apply to permitted development projects. Read our guide →
Party wall notices may be needed for work on or near a shared wall. Read our guide →
Build-over agreements are needed near public sewers. Structural engineering guide →