Permitted Development can also apply to extensions without a planning application, subject to limits:
Single-storey rear extension:
Up to 3 m (attached houses) or 4 m (detached) deep.
Overall coverage:
New extensions must not cover more than 50% of the land around the original house.
Height limits:
Max 4 m for rear/side extensions.
Even if you think your project comes under PD rights, you will need planning permission if any of the following apply:
Conservation Area, Article 4 Direction or Listed Building
Properties in conservation areas or with Article 4 directions may lose permitted development rights, meaning even small extensions need full planning permission.
Extensions Exceeding Limits
Work that exceeds PD allowances — wrap-around extensions, or roof enlargements that breach size limits — will require planning approval.
Flats and Maisonettes
Most extensions in flats or maisonettes do not benefit from standard house PD rights and usually need planning permission.
Significant Visual or Structural Changes
Changes that materially alter your home’s appearance (e.g., significant rear additions visible from public spaces) will often trigger planning approval.
Even if your project doesn’t require planning permission, you can apply for a Lawful Development Certificate. This provides written confirmation from the council that your work falls under Permitted Development, giving legal certainty and helping with future sales of the property.
London boroughs can interpret policies slightly differently. Always consult with the local planning authority (LPA) before starting work — either directly or via an architect/planning consultant — to confirm whether permitted development rights apply and whether any local restrictions are in place.
| Project Type | Permitted Development? | Planning Permission Needed? |
|---|---|---|
| Rear extension within PD size | Yes | No |
| Side or wrap-around extension exceeding limits | No | Yes |
| Properties in conservation areas | Often no | Yes/conditional |
| Flats/maisonettes | No | Yes |
Whether or not planning permission is needed, Building Regulations approval is always required for extensions and loft conversions. This ensures:
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