Do You Need Planning Permission for a Conservatory? (UK Rules)
When a conservatory needs planning permission in the UK: the 3m and 4m depth limits, height rules, the larger home extension scheme, and when it's exempt from building regulations.
By Adam Mokhtar, Founder · · 3 min read
Quick answer
A conservatory counts as a single-storey extension, so it's permitted development without planning permission if it extends no more than 3m from the rear of an attached house or 4m from a detached one, is no higher than 4m, isn't in front of the house, and keeps total extensions under half the garden. In England you can go to 6m or 8m under the larger home extension scheme with prior approval. It's exempt from building regulations only if it's separated from the house by proper doors, under 30m², and has its own heating controls.
Do You Need Planning Permission for a Conservatory? (UK Rules)
A conservatory is, in planning terms, just an extension that happens to be mostly glass. So the rules are the extension rules. Most conservatories fit within them and need no planning permission. Here's how to check, and the separate question of building regulations, which trips more people up than planning does.
Planning permission: the permitted development limits
You don't need planning permission if the conservatory meets all of these:
- Depth. It extends no more than 3m beyond the rear wall of an attached house, or 4m for a detached house.
- Height. No more than 4m to the ridge, and no more than 3m to the eaves if any part is within 2m of a boundary.
- Position. Not in front of the principal elevation, and not to the side if the house is on designated land.
- Coverage. Together with all other extensions and outbuildings, it covers no more than half the garden around the original house.
- Materials. Similar in appearance to the existing house, which glass extensions generally satisfy.
In England, the larger home extension scheme lets a single-storey rear extension go to 6m (attached) or 8m (detached) through a prior-approval application. The council notifies the neighbours and can refuse if they object on reasonable grounds. This scheme doesn't exist in Wales, where the 3m and 4m limits stand.
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Book a free Build, Wait or Move CallListed buildings always need consent. Conservation areas, National Parks and Areas of Outstanding Natural Beauty remove permitted development for side extensions and anything clad in non-matching materials. If your home is on a newer estate, check whether permitted development rights were removed by the original permission.
Building regulations: where conservatories are different
This is the part that matters. A conservatory is exempt from building regulations only when it is:
- at ground level and under 30m² floor area,
- separated from the house by external-quality doors, windows or walls,
- fitted with its own heating system with independent controls, and
- glazed and wired to the relevant safety standards.
Take out the doors between the kitchen and the conservatory, and you've created an extension. Now the thermal performance of the combined space is judged under building regulations, and a glass roof and thin frames don't meet it. That's why "open-plan conservatory" projects usually end up with an insulated solid roof, at which point they're extensions in all but name.
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Book a free Build, Wait or Move CallConservatory or extension?
The honest comparison:
- Conservatory: cheaper to build, quick, exempt from building regulations if kept separate. Hot in summer, cold in winter, and often becomes the room the dog sleeps in.
- Single-storey extension with big glazing: more expensive, needs building regulations, but it's a real room you'll use every day and it adds more value.
If what you actually want is more kitchen, more dining space or a room that's part of the house, read our guide to house extension or conservatory before you commit to the cheaper option.
Check your home
Run it through the planning checker, find your council with the local authority finder, and if you want a real number for an extension instead, the extension cost calculator gives you a realistic range in a minute.
Frequently asked questions
How big can a conservatory be without planning permission?
In England and Wales, up to 3m deep on an attached house or 4m on a detached one, no more than 4m high (3m if within 2m of a boundary), not forward of the principal elevation, and not covering more than half the garden with everything else. In England the larger home extension scheme allows 6m or 8m with a prior-approval application to the council.
Does a conservatory need building regulations?
It's exempt if it's at ground level, under 30m² floor area, separated from the house by external-quality doors or walls, has its own heating with separate controls, and the glazing and electrics meet the relevant standards. Open it up to the house, or go over 30m², and the full building regulations apply as they would to any extension.
Can I knock through from the kitchen into the conservatory?
Yes, but it then stops being an exempt conservatory and becomes an extension. The thermal performance of the whole room has to meet building regulations, which usually means a proper insulated roof and better glazing. Many people find at that point a lightweight extension is better value than a conservatory.
Is a conservatory cheaper than an extension?
To buy, usually. To live in, often not: a glazed roof is cold in winter and hot in summer, and the room gets used less than people expect. If you want a room you'll use all year, compare it against a single-storey extension with large glazing before deciding.