Do I need planning permission?
Many extensions and loft conversions don't need a full planning application — they fall under permitted development. But the limits are strict, and going a few centimetres over changes everything.
Answer a few questions and we'll tell you what the national rules say about your project — and exactly which rule you're up against.
Please read: this tool gives general information, not advice. It checks the main size limits under the national permitted development rules for England — it cannot see your property, its planning history or any local restrictions. Do not start work on the basis of this tool alone: confirm with your local planning authority or apply for a Lawful Development Certificate first.
What are you building?
⚠️ Important — this is general information, not advice, and not a decision.
- It checks the main size and height limits only. Permitted development carries other conditions — materials must be similar in appearance, nothing may project forward of the principal elevation fronting a highway, and more.
- It cannot see your property. Article 4 directions, planning conditions on newer estates, listed status, or the property being a flat can all remove permitted development rights entirely.
- Restrictive covenants on your title deeds are a separate, private legal matter — planning permission does not override them.
- Never start work on the basis of this tool alone. Confirm with your local planning authority, or apply for a Lawful Development Certificate, before you build.
Cheshire Design & Build NW accepts no liability for any loss arising from reliance on this tool. Rules apply to England only and are correct as at July 2026.
Rules verified against the official Planning Portal guidance for England (July 2026). England only — Scotland, Wales and Northern Ireland differ.
The permitted development rules, in plain English
Permitted development is a national grant of planning permission written into law. It lets you build certain things without applying to the council — as long as you stay inside the limits. Here's what those limits actually are.
Single-storey rear extensions
- Depth: up to 4m beyond the original rear wall for a detached house, or 3m for any other house (semi-detached, terraced).
- Larger extensions: up to 8m (detached) or 6m (any other house) are possible under the larger home extension prior-approval scheme — you notify the council, and neighbours can object. Not available on designated land.
- Height: no more than 4m at the highest point.
- Near a boundary: if the extension comes within 2m of a boundary, the eaves must be no more than 3m high.
- Ground cover: extensions and outbuildings together must not cover more than half the land around the original house.
Two-storey rear extensions
- Must not extend more than 3m beyond the original rear wall.
- Must not come within 7m of the boundary opposite the rear wall.
Side extensions
- Must be single storey, no more than 4m high.
- Width must be no more than half the width of the original house.
- Not permitted development at all on designated land — a conservation area side extension needs full planning permission.
Loft conversions
- Volume: up to 40m³ for a terraced house, or 50m³ for a semi-detached or detached house.
- Must not extend beyond the roof slope on the principal elevation (the side fronting the road).
- Must not be higher than the existing roof.
- Set back at least 20cm from the original eaves, where practicable (hip-to-gable is treated differently).
- Side-facing windows must be obscure-glazed, and non-opening below 1.7m from the floor.
- No balconies, verandas or raised platforms.
- No permitted development rights on designated land.
What can take your rights away
Permitted development is not guaranteed. It can be removed by an Article 4 direction (common in conservation areas), by a planning condition on a newer housing estate, or because the property is a flat, maisonette or listed building — none of which have these rights in the first place.
That's why the safe route, if you're anywhere near a limit, is a Lawful Development Certificate — a formal council confirmation that your project is lawful. It isn't compulsory, but a buyer's solicitor will very often ask for it when you come to sell.
Building in Warrington?
Four of Warrington's most desirable villages — Stockton Heath, Grappenhall, Lymm and Walton — sit inside conservation areas, which removes permitted development rights for side extensions and loft conversions entirely. See our guide to planning permission in Warrington.
Planning permission isn't the only permission you need
The Party Wall etc. Act is completely separate from planning — and it catches people out. You can have full planning permission and still be acting unlawfully if you haven't served notice on your neighbour. Standard extension foundations often trigger it. Check with our free party wall checker.
Thinking about a project?
We handle planning applications, permitted development and LDC applications and Building Regulations in-house — as part of a fully managed extension, loft conversion or kitchen extension. We check all of this at the free site visit before you commit to anything.
Planning Permission FAQs
Do I need planning permission for an extension?
Not always. Many single-storey rear extensions fall under "permitted development", which means you can build without a full planning application — provided you stay within strict limits on depth, height and how close you build to the boundary. A detached house can extend up to 4m beyond the original rear wall; any other house up to 3m. Go beyond that and you either need prior approval under the larger home extension scheme, or full planning permission.
What is permitted development?
Permitted development rights are a national grant of planning permission, set out in law, that let you carry out certain works without applying to the council. They come with strict conditions on size, height, position and materials. They can also be removed — by an Article 4 direction, by a planning condition on a newer property, or because the property is a flat or a listed building.
How far can I extend without planning permission?
For a single-storey rear extension: 4m beyond the original rear wall for a detached house, or 3m for a semi-detached or terraced house. Under the larger home extension prior-approval scheme this can rise to 8m (detached) or 6m (other houses), but that requires notifying the council and is not available on designated land such as a conservation area.
Does a loft conversion need planning permission?
Often not. Loft conversions are usually permitted development if the added volume stays within 40 cubic metres for a terraced house, or 50 cubic metres for a semi-detached or detached house, and the work does not extend beyond the roof slope on the front elevation, does not go higher than the existing roof, and includes no balcony or veranda. On designated land (conservation areas and similar) these rights do not apply.
What is a Lawful Development Certificate, and do I need one?
It is a formal council document confirming your project is lawful under permitted development. It isn't compulsory — but it removes all doubt, and a buyer's solicitor will very often ask for it when you come to sell. We prepare and submit LDC applications in-house.
Is this checker legal advice?
No. It is indicative guidance based on the national permitted development rules, and it cannot see your property, your title, your planning history or any local restrictions. Article 4 directions, conservation areas, listed status and conditions on newer estates can all remove permitted development rights entirely. Always get it confirmed before you build — that is exactly what our free site visit and Lawful Development Certificate service is for.
Not sure where you stand?
Book a free site visit. We'll tell you straight whether your project is permitted development, and handle the application either way.