What is a Lawful Development Certificate?

A Lawful Development Certificate (LDC) is a formal confirmation from your local planning authority that your proposed work is lawful under permitted development rights. It costs approximately £120 for a householder application (half the planning application fee). While not legally required, it provides certainty and is useful when selling the property.

What is the 50% garden coverage rule?

The total area of ground covered by extensions, outbuildings and other additions must not exceed 50% of the total area of the curtilage (garden). This includes existing extensions, sheds, garages and any other structures. The original house footprint is not counted — only additions since the house was first built (or since 1948).

What are the rear depth limits for PD?

Semi-detached and terraced houses: maximum 3m rear extension depth (or 6m with prior notification). Detached houses: 4m (or 8m with prior notification). Depth is measured from the original rear wall. The larger extension scheme (prior notification) does not apply in conservation areas, AONB or National Parks.

Are there height limits for PD extensions?

Yes. Single storey rear extensions: maximum eaves height 3m, overall height 4m. Side extensions: single storey only, maximum height 4m, must not be wider than half the original house. Two storey rear: maximum eaves 3m from boundary, no closer to boundary than 7m. Ridge must not exceed existing house ridge.

What restrictions apply in conservation areas?

In conservation areas (and AONB, National Parks, World Heritage Sites): no side extensions under PD, no cladding, rear extensions limited to standard depths (no larger extension scheme), no roof additions visible from a highway, materials must match existing. Always check with your local authority as Article 4 directions may apply.

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Lawful Development Checker — Permitted Development Assessment

Check whether your proposed extension or outbuilding falls within permitted development rights based on rear depth, height, garden coverage and designations.

House type

Rear extension depth

Side extension height

Rear extension height

Total garden area

Existing built area in garden

How We Calculate This

This checker assesses proposed development against the key permitted development criteria in the GPDO 2015 (as amended).

Checks performed

Rear extension depth vs PD limits
Side and rear extension heights
Ridge height comparison with existing
Garden area coverage (50% rule)
Conservation area, listed building, AONB restrictions

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Verify with your supplier.