What can I build without planning permission?

In the UK, homeowners have a surprising amount of latitude to build, extend, and alter their homes without applying for planning permission. It’s called permitted development, and it’s set out in a single piece of legislation — the General Permitted Development Order 2015. This guide covers everything that permitted development typically allows, the things that remove those rights, and how to know for certain at your own property.

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What is permitted development?

Permitted development is a legal shortcut. Parliament decided that some home improvements are so common and so low-impact that they shouldn’t need a full planning application every time. Instead, a national framework lists exactly what you can do — and the limits you have to stay within — for each type of project. If your work meets the rules, you don’t need to apply to your council before starting.

The rules are grouped into numbered “classes” — Class A for house enlargements, Class B for loft conversions, Class C for roof alterations, and so on. Each class has its own dimension limits and conditions. Miss even one and the project falls outside permitted development, which means you’ll need to apply for planning permission or redesign.

Even when a project is permitted development, it’s usually worth applying for a Lawful Development Certificate afterwards. The LDC gives you official confirmation from your council that the work was lawful, which is valuable when you sell the property. We publish a free step-by-step LDC application pack — enter your details and we generate the supporting statement for you.

What you can build under permitted development

Here are the most common projects UK homeowners carry out under permitted development, with the headline limits for each. Follow the links for the full rules and typical costs.

Rear extensions

Single storey rear extensions up to 3m deep on terraced and semi-detached houses, or 4m deep on detached houses. Maximum eaves height 3m, overall height 4m. Two-storey rear extensions are permitted up to 3m in depth but must stay at least 7m from the rear boundary. Conservation areas and listed buildings have tighter limits or no rights at all. See the rear extension guide for the full rules.

Loft conversions

Class B allows up to 40 m³ of additional roof space on terraced houses, or 50 m³ on semi-detached and detached houses. Dormers are permitted on rear and side slopes but not on the principal elevation (the front, if it faces a highway). The ridge line can’t be raised. See the loft conversion guide for the detailed rules.

Side extensions

Single storey side extensions on houses are permitted development as long as they stay under 4m in height, don’t exceed half the width of the original house, and are built with matching materials. Side extensions are not permitted development in conservation areas — they’re specifically removed by the GPDO for Article 2(3) designated land. See the side extension guide.

Outbuildings, garden rooms and home offices

Class E covers detached outbuildings — sheds, summer houses, home offices, garden rooms. They must sit behind the front elevation, not exceed 2.5m in height if within 2m of any boundary, and the total area of outbuildings combined with extensions can’t exceed 50% of the garden. Crucially, an outbuilding can’t be used as a self-contained dwelling — no permanent sleeping, kitchens, or full bathrooms. See the outbuilding guide for the full detail.

Porches

Class D allows a front porch up to 3 m² in floor area, 3m in height, and at least 2m from any highway. Listed buildings are the main exception — they always need listed building consent for alterations. See the porch guide.

Solar panels

Solar PV and thermal panels on the roof of a house are permitted development under Part 14 of the GPDO, provided they don’t protrude more than 0.2m from the roof slope and aren’t installed on a listed building. In conservation areas, panels on slopes facing a highway need full planning permission. Standalone (ground-mounted) arrays are more restrictive.

Fences, walls and gates

Part 2, Class A allows fences, walls, and gates up to 2m in height elsewhere, or 1m if adjacent to a highway. Listed buildings need consent for any boundary alterations.

Roof alterations

Class C allows re-roofing, rooflights (as long as they don’t protrude more than 0.15m from the roof plane), and similar alterations. Materials should be similar in appearance to the existing roof. Listed buildings are excluded.

What you can’t build without planning permission

Some projects always need planning permission, regardless of their size or location. The main categories are:

•Basements. There are no permitted development rights for new basements beneath a house or garden — excavation always requires a full planning application.
•Front extensions. Any extension forward of the principal elevation facing a highway falls outside Class A. Porches under 3 m² are the only exception.
•Anything exceeding the dimension limits. A 5m rear extension, a 60 m³ loft addition, a 3m-high garden room within 1m of a boundary — all outside the rules, all need an application.
•External alterations to listed buildings. Including windows, doors, paint colour changes, and satellite dishes. Separate listed building consent is needed on top of (or instead of) planning permission.
•Changes of use. Turning a house into flats, adding a commercial use, or converting a garage into a separate dwelling all require planning permission or prior approval.
•Anything on a flat or maisonette. Most Class A permitted development rights only apply to houses, not flats. Flat owners can’t extend under PD.

Six things that can remove your permitted development rights

Even projects that normally qualify can lose their permitted development status because of the property itself. Before assuming the rules apply to you, check for the following:

1. Listed building status. All external work needs listed building consent. Interior works to listed buildings may need it too.
2. Conservation area. Class A side extensions, cladding, and some other rights are removed entirely. Rear extensions have tighter size limits. Every conservation area has a character appraisal the council will reference.
3. Article 4 Direction. Councils can withdraw specific permitted development rights in a defined area — typically a street or group of streets where the council wants closer control. Common in London boroughs with historically-significant terraces.
4. Designated land. National Parks, Areas of Outstanding Natural Beauty (AONBs), World Heritage Sites, and The Broads all reduce or remove Class A rights through Article 2(3). If you’re in one, the national limits are usually halved.
5. Flood zones. Properties in flood zones 2 and 3 have restricted PD rights for certain types of outbuilding and hard landscaping. A Flood Risk Assessment is typically required.
6. Previous extensions. PD rights are cumulative across the life of the property. If a previous owner already extended, your allowance shrinks. If the total coverage of extensions and outbuildings exceeds 50% of the curtilage, no new PD extensions are allowed.

How to know for sure at your property

Permitted development is national law, but whether your specific project qualifies depends on your specific house, street, and plot. You have three ways to find out.

1. Free online check (fastest)

Enter your postcode on our free check. We pull the live constraints affecting your property — conservation area, Article 4, listed status, flood zone, TPO — and apply the GPDO rules to the project you’re planning. Results in 2 minutes.

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2. Lawful Development Certificate (official)

The LDC is an application to your council for legal confirmation that your planned work is permitted development. It takes about 8 weeks and there’s a fee (currently £129 for a proposed-use LDC). It’s the only way to get certainty backed by law, and it’s usually worth having before you sell the property. We generate the full application pack for free — see the LDC guide.

3. Pre-application advice (council-by-council)

Most councils offer a paid pre-application advice service where a planning officer gives you an indicative opinion on a proposal. It’s non-binding but useful for borderline cases. Fees vary by council (typically £50–£300 for a householder query).

What if my project doesn’t qualify as permitted development?

If your project falls outside the limits — or your property has restrictions that remove PD rights — you’ll need a full planning application. The current statutory fee for a householder application is £258, and most councils aim to decide within 8 weeks of validation. Approval rates vary enormously by borough and project type, and the single biggest factor in whether your application gets approved is how well it’s been designed around the specific constraints at your property.

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Frequently asked questions

Can I build a rear extension without planning permission?

In most cases, yes — provided you stay within the GPDO 2015 dimension limits. For a single storey rear extension, that means up to 3m from the rear wall on a terraced or semi-detached house (4m for detached), a maximum eaves height of 3m, and an overall height of 4m. Two-storey rear extensions are allowed up to 3m in depth but must stay 7m from the rear boundary. These limits shrink or disappear if your property is in a conservation area, listed, or under an Article 4 Direction.

Do loft conversions need planning permission?

Most loft conversions qualify as permitted development under Class B of the GPDO. The key limits are the volume of roof space added (up to 40 m³ for terraced houses, 50 m³ for semi-detached and detached), no dormers on the principal front elevation, no raised ridge line, and matching materials. If any of those limits are exceeded, or you’re in a conservation area, a full planning application is usually needed.

Can I build a garden room or outbuilding without planning permission?

Garden rooms, home offices, sheds and similar outbuildings fall under Class E of the GPDO. You can typically build one as permitted development if it sits behind the front elevation, doesn’t exceed 2.5m in height when within 2m of a boundary (4m otherwise, with a 3m eaves cap), and the total outbuilding coverage stays under 50% of your garden area. Use as a self-contained living space (with a kitchen and bathroom) removes those rights.

What’s the difference between permitted development and planning permission?

Permitted development is a national legal shortcut — the General Permitted Development Order 2015 — that lets you carry out certain types of work without applying to your council. Planning permission is the formal application process you use when your project falls outside those permitted-development limits. Permitted development is faster and cheaper (no application fee), but you should still consider applying for a Lawful Development Certificate to prove your work was lawful if you sell the property later.

What stops a project from being permitted development?

The main blockers are: the property being a listed building (all external alterations need consent), being a flat or maisonette (most Class A rights do not apply), being in a conservation area (Class A side extensions and cladding are removed), an Article 4 Direction on your street (removes specific PD rights locally), exceeding the dimension limits, or having already used up too much of the 50% curtilage coverage with previous extensions.

How do I know for sure what I can build at my property?

Three options, in increasing order of certainty. Free: run a 2-minute check on whatcanibuild.co.uk using your postcode — we pull the live constraints on your property and apply the GPDO rules to your project. Official but slower: apply to your council for a Lawful Development Certificate, which gives you legal confirmation. Paid advisory: book a pre-application advice session with your council’s planning team for a non-binding opinion on a specific proposal.

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