What is permitted development?

Permitted development (PD) rights allow certain building works and changes of use without needing to apply for planning permission. They are set out in the Town and Country Planning (General Permitted Development) Order 2015 (as amended). PD rights apply to most houses but not to flats, listed buildings, or properties where an Article 4 direction applies.

What is the maximum depth for a rear extension under PD?

For detached houses, the maximum projection is 4m for a single-storey rear extension. For semi-detached and terraced houses, it is 3m. These are measured from the rear wall of the original house. Under the prior notification scheme, depths of up to 8m (detached) or 6m (semi/terrace) may be possible — check with your council.

What are the PD rules for outbuildings?

Outbuildings must: not cover more than 50% of the garden (curtilage), not be forward of the principal elevation, have a maximum height of 2.5m within 2m of a boundary, 4m with a dual pitch roof or 3m otherwise. They must be ancillary to the dwelling (not a separate dwelling) and cannot contain sleeping accommodation as the primary use.

Do conservation areas affect permitted development?

Yes, conservation areas restrict some PD rights. Specifically: no cladding, no dormer windows on roof slopes facing the highway, no satellite dishes on front elevations, and side extensions are restricted. Outbuilding rules remain mostly the same. Always check with your local authority as some areas have additional restrictions via Article 4 directions.

Do I still need Building Regulations approval under PD?

Yes! Permitted development only relates to planning permission. You still need Building Regulations approval for structural work, electrical installations, drainage, and any habitable extensions. Building control must inspect and approve the work regardless of whether planning permission was needed.

Permitted Development Checker

Check if your extension, outbuilding or loft conversion falls within permitted development rights under the GPDO (England). Quick reference tool.

Property Type

Affects depth and volume limits

Project Type

Type of development to check

Extension Depth / Projection

Projection from rear wall

Eaves Height

Height to eaves of extension

Ridge Height

Must not exceed existing house ridge

Distance to Boundary

From extension to nearest boundary

Listed building

Listed buildings have no PD rights

Conservation area

Some PD rights are restricted

Article 4 direction

Specific PD rights removed

How We Calculate This

This checker compares your proposed development against the key dimensional limits set out in the General Permitted Development Order (GPDO) for England. It checks depth, height, ridge height, boundary distance and coverage rules.

The checks

Rear extension: Max 3m (semi/terrace) or 4m (detached) depth
Outbuilding: Max 50% garden coverage, 2.5m height at boundary
Loft: Max 40m³ (terrace) or 50m³ (other) additional volume
Side extension: Max half original house width, 4m height

This is a guidance tool only. Always verify with your local planning authority before starting work. Rules vary and may have been amended since this tool was updated.

Key exclusions

Listed buildings have NO PD rights
Flats have very limited PD rights
Article 4 directions remove specific PD rights
Conservation areas restrict some external works

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.