Permitted Development Rights for Extensions in London — 2026 Rules

Permitted development rights (PD) let you build certain extensions without applying for full planning permission. For London homeowners, getting this right can save you 8-12 weeks of planning time and a planning consultant's fees. But the rules are full of caveats — and London-specific Article 4 directions strip PD rights from many areas. Here's the 2026 guide.

What permitted development rights actually are

PD rights are a national scheme defined by the Town and Country Planning (General Permitted Development) Order 2015 — updated multiple times since. They let you do certain types of building work without applying for full planning permission. Building Regs still apply, but you skip the planning application + 8-12 week wait.

Single-storey rear extensions — the headline PD right

Under the standard PD rules, you can build a single-storey rear extension:

• Terraced or semi-detached: up to 3m deep, 4m maximum eaves height
• Detached: up to 4m deep, 4m maximum eaves height

Under the 'larger home extension' PD right (which requires a prior approval notification — see below), you can go further:

• Terraced or semi-detached: up to 6m deep
• Detached: up to 8m deep

Prior approval — what it is, what it isn't

For larger PD extensions (those over 3m/4m depth), you must notify the council and let neighbours object via a prior approval process. It is NOT full planning permission. The council can only refuse based on the impact on neighbours' amenity — they cannot consider design, materials, or wider planning concerns.

Process: submit notification + drawings + neighbour notification list. Council has 42 days. If no neighbours object, approval is automatic. If a neighbour objects, the council assesses the objection on amenity grounds only.

Fee: £103 (2026). Much lower than full planning. Architectural drawings still needed.

Double-storey rear extensions under PD

Two-storey rear extensions are allowed under PD but with strict limits:

• Maximum depth: 3m
• Cannot extend higher than the existing roof eaves
• Cannot be within 7m of any rear boundary
• Materials must be similar to the existing house
• Roof pitch should match the existing where possible

Most London terraces have less than 7m to the rear boundary — making this PD route unavailable in practice. Result: most London double-storey extensions need full planning permission.

Side extensions under PD

Side extensions are allowed under PD but only:

• Single-storey
• Up to half the width of the original house
• Up to 4m eaves height
• Not facing a highway (front-facing side extensions need planning)

On a typical 5-6m wide London terrace, a 1.5-2m side extension is at or above the half-width limit — so most London side-return extensions need full planning.

The London-specific traps

Conservation areas

London has hundreds of designated conservation areas. PD rights are heavily restricted in conservation areas — typically:

• Side extensions: no PD rights at all (always need planning)
• Rear extensions: depth limits cut to 3m max (no larger PD route)
• Cladding, painting brickwork, replacing windows: removed from PD
• Roof extensions / dormer windows: usually removed from PD

Article 4 directions

Some London boroughs have issued Article 4 directions that remove specific PD rights in defined areas. Examples:

• Camden, Hackney, Islington — Article 4 directions on Victorian terraces in many wards removing PD for rear extensions, dormer windows, and external cladding
• Wandsworth, Westminster — Article 4 in conservation areas removing PD for windows, roofs, external doors
• RBKC, City of Westminster — almost total removal of PD across the borough through combined Article 4 directions and conservation designation

Always check your specific address on the borough's interactive planning constraints map BEFORE assuming PD applies.

Listed Buildings

If your property is Listed, PD rights are essentially removed for any external alteration. You need Listed Building Consent on top of any planning permission.

Flat conversions

Flats (including flats above shops) generally do not have any PD rights for extensions. Always need full planning.

How to check if PD applies to your property

1. Go to your local borough's planning portal (e.g. Wandsworth, Camden, etc.)
2. Search for your address on the interactive constraints map
3. Look for: Conservation Area, Article 4 direction, Listed Building, World Heritage Site
4. If none of those apply, check the dimension limits above against what you're planning
5. If in doubt, request a Lawful Development Certificate (£103-258) — gives legal confirmation that your proposed extension is PD

The Lawful Development Certificate — worth it

A Lawful Development Certificate (LDC) is a formal planning document confirming that your proposed extension is permitted development. Cost: £103-258. Timeline: 6-8 weeks.

Why bother if PD doesn't need planning? Because it protects you on resale. When you sell, the buyer's conveyancer will ask 'has any extension or alteration been done in the last 4 years?' An LDC is documentary proof that everything was legal. Without it, buyers can demand indemnity insurance (£200-400 cost) or even pull out of the purchase. £103 now saves headaches later.

When you DEFINITELY need full planning permission

• Any double-storey extension on a terrace within 7m of the rear boundary
• Most side extensions on London terraces (half-width rule)
• Anything in a conservation area beyond the smallest PD limits
• Any work to a Listed Building
• Any extension on a flat
• Extensions where the property has already used up its PD allowance from previous owners
• Mansards and certain dormer loft conversions in conservation areas

Frequently asked questions

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