Can I build an extension without planning permission?

Yes, under permitted development rights, you can build a single-storey rear extension up to 4 metres deep for a detached house (or 3 metres for semi-detached/terraced) without planning permission, or up to 8 metres/6 metres under the larger home extension scheme (with prior approval). The extension must not be higher than 4 metres, must not cover more than half the garden area, and must meet other conditions. Side extensions, front extensions, and two-storey extensions have different, more restrictive rules.

Do I still need Building Regulations approval for permitted development?

Yes — permitted development only removes the need for PLANNING PERMISSION. You still need to comply with Building Regulations for any structural work. This means building control will need to inspect and approve foundations, structure, insulation, electrics, drainage, and fire safety. You'll need either a local authority building control sign-off or an Approved Inspector. Building without Building Regulations approval is a legal offence and will cause serious problems when you sell.

Do flats have permitted development rights?

Flats and maisonettes generally have very limited permitted development rights compared to houses. You cannot extend a flat under PD rights. Some minor works may be permitted (e.g. internal alterations that don't affect the external appearance), but most external changes will need planning permission. You'll also typically need the freeholder's (landlord's) consent and potentially lease consent for any alterations to a flat, even internal ones.

Permitted Development Rights Guide UK — What You Can Build Without Planning Permission | PocketWise

Q: What are permitted development rights?

Permitted development (PD) rights allow you to carry out certain building works and changes of use without needing to apply for planning permission from your local council. They're set by the government through the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended). Common examples include small single-storey rear extensions, loft conversions (within limits), outbuildings, and changes from commercial to residential use. PD rights have specific size limits, conditions, and restrictions that must be met.

Permitted development rights let you make many changes to your home without applying for planning permission. Here’s what you can and can’t do.

What Are Permitted Development Rights?

Feature	Detail
What they are	Government-granted rights to make certain changes without planning permission
Applies to	Houses (not flats, maisonettes, or converted houses, in most cases)
Legislation	Town and Country Planning (General Permitted Development) Order 2015 (as amended)
Still need Building Regs?	Yes — always
Still need Party Wall consent?	Yes — if work affects a shared wall or is near a neighbour’s property

Rear Extensions — Without Planning Permission

Single-Storey Rear Extension

Rule	Detached house	Semi-detached / terraced
Maximum depth from original rear wall	4 metres (or 8m with prior approval)	3 metres (or 6m with prior approval)
Maximum height	4 metres	4 metres
Maximum eaves height	3 metres	3 metres
No higher than the existing house	Must not exceed roof height	Must not exceed roof height
Materials	Must be similar to the existing house	Must be similar
Maximum site coverage	Cannot cover more than 50% of the garden area (including all outbuildings)	Same

Two-Storey Rear Extension

Rule	Requirement
Maximum depth	3 metres from original rear wall
Maximum eaves height	Must not be higher than existing eaves
Must be at least 7 metres from rear boundary	Measured from the rear wall of the extension
Materials	Must match the existing house
Windows	Obscure glazed and non-opening (unless 1.7m above floor) on upper floor side-facing windows

Side Extensions

Rule	Requirement
Single storey only	Under PD
Maximum width	No more than half the width of the original house
Maximum height	4 metres
Cannot be forward of the principal elevation	Must not project in front of the main face of the house
On a designated land	Not permitted (conservation areas, AONB, National Parks, etc.)

Larger Home Extension Scheme (Prior Approval)

Feature	Detail
Extended limits	Single-storey rear extension up to 8m (detached) or 6m (semi/terraced)
Process	Apply to council for prior approval (not full planning)
Council consults neighbours	Neighbours have 21 days to comment
Decision	Council decides within 42 days
Cost	£120 (much less than a full planning application)
If no response from council in 42 days	Deemed approved

Loft Conversions

Rule	Detached house	Semi-detached / terraced
Maximum additional volume	50 cubic metres	40 cubic metres
Must not be higher than existing roof	No increase to the highest part of the roof	Same
Dormer position	Not on front elevation facing a highway	Same
Materials	Must be similar to the existing house	Same
Side-facing windows	Obscure glazed, non-opening below 1.7m	Same
Balconies/verandas/raised platforms	Not permitted under PD	Same
Roof extension on principal elevation	Not permitted	Same

Outbuildings (Sheds, Summerhouses, Garages)

Rule	Requirement
Maximum height (flat roof)	2.5 metres
Maximum height (dual pitch)	4 metres
Maximum height (other)	3 metres
Maximum eaves height	2.5 metres
Position	Not forward of the principal elevation
Site coverage	All outbuildings (including the new one) must not exceed 50% of the garden
If within 2m of boundary	Maximum height 2.5 metres
Use	Incidental to the enjoyment of the house — not a separate dwelling, business premises, or bedroom

Other Works Under PD

Work	Key limits
Porch	Max 3 sqm floor area, max 3m height, 2m from highway
Driveway/hard standing	Must use permeable surface (or drain to lawn/border)
Fences, walls, gates	Max 1m next to a highway, 2m elsewhere
Solar panels	On roof (not higher than roof, not on listed buildings)
Satellite dish	1 per property, size limits, not on chimney or front-facing in conservation area
Painting the exterior	Usually permitted (not in conservation areas if it significantly changes appearance)
Internal alterations	Always permitted (but Building Regs may apply for structural changes)

When PD Rights Do NOT Apply

Situation	Detail
Listed buildings	Most external (and many internal) changes need listed building consent
Conservation areas	Restrictions on side extensions, cladding, satellite dishes, dormer windows, etc.
AONB / National Park / Broads	Similar restrictions to conservation areas
Flats and maisonettes	Very limited PD rights
Article 4 direction	Council has removed specific PD rights in your area
Conditions on original planning	PD rights may have been removed when the house was first built
New-build estate	PD rights may have been removed by planning condition

How to Check

Method	Detail
Lawful Development Certificate	Apply to council (£258) — they confirm in writing whether your work is permitted development
Pre-application advice	Ask the council for informal advice before starting
Check planning conditions	Look at any existing planning permissions on your Property
Check Article 4 directions	Available on your council’s website

Prior Approval vs Planning Permission

Feature	Prior approval	Full planning permission
For	Specific PD activities (large extensions, some changes of use)	Any development not covered by PD
Cost	£120 (extensions)	£258 (householder application)
Decision time	42 days	8 weeks (13 for major applications)
Neighbour consultation	Council consults directly	Council consults and considers objections
Conditions	Limited	Can impose wide-ranging conditions
If not determined in time	Deemed approved	Deemed refused (you can appeal)

Common Mistakes to Avoid

Mistake	Consequence
Not checking if PD rights have been removed	Work may be unlawful — you could be ordered to demolish
Exceeding PD limits even slightly	Entire extension becomes unauthorised
Not getting Building Regulations sign-off	Problems when selling, potential enforcement action
Forgetting about Party Wall Act	Can lead to disputes, injunctions, and costs
Assuming all houses have PD rights	Flats, converted houses, and some new builds do NOT
Not getting a Lawful Development Certificate	No proof your work was lawful if challenged later