Permitted Development Rights for Extensions — Complete London Guide

Permitted development rights are a set of national planning permissions granted by the government to allow certain types of development without needing planning permission. They are set out in the Town and Country Planning (General Permitted Development) (England) Order 2015.

For homeowners, the relevant part is Schedule 2, Part 1, Classes A–H — covering extensions, loft conversions, outbuildings, porches, and other alterations.

Permitted development does not mean unregulated. Even where planning permission is not required, Building Regulations approval usually is.

Before checking what you can build, confirm that permitted development rights apply to your property:

PD rights are removed or restricted if:

• You live in a conservation area (many London boroughs have extensive conservation areas)
• An Article 4 Direction has been made, removing PD rights for specific types of work in an area
• Your property is a listed building (permitted development does not apply to listed buildings — listed building consent is required for most alterations)
• Your property is a flat or maisonette (PD rights under Part 1 only apply to houses)
• The property is in a National Park, Area of Outstanding Natural Beauty, or similar designated area
• Conditions attached to previous planning permissions have removed PD rights

In London, Article 4 Directions are very widespread. Many Victorian residential streets in inner London have had PD rights removed for front elevations, side returns, and rear extensions. Always check with your local planning authority before assuming PD applies.

Single-storey rear extensions:

• Detached houses: up to 4m depth from the original rear wall
• Other houses (terraced, semi-detached): up to 3m depth from the original rear wall
• Maximum 4m eaves height (measured to the underside of the eave)
• Must not exceed the ridge height of the original roof
• Must not extend beyond the width of the original house
• Materials must be similar in appearance to the existing house

Larger extensions via Prior Approval (Neighbour Consultation Scheme):

• Detached houses: up to 8m depth
• Other houses: up to 6m depth
• Must notify the local authority before starting
• Neighbours are consulted — objections can lead to full planning requirement
• This is not the same as having no need to notify — prior approval must be obtained before works start

Two-storey rear extensions:

• Maximum 3m depth beyond original rear wall
• No closer than 7m to the rear boundary
• Maximum 4m eaves height and 4m ridge height at the eave, or same as original roof ridge height

Side extensions are more restricted under PD:

• Maximum half the width of the original house
• Single-storey only under PD (two-storey side extensions require planning permission)
• Cannot be forward of the front elevation
• In conservation areas: usually removed entirely by Article 4

Side return extensions in Victorian terraces are technically a side extension and subject to these restrictions. In many London conservation areas, side return extensions require planning permission.

Dormer windows and roof extensions (Class B):

• May not exceed the highest part of the roof
• Total volume added must not exceed 40m3 for terraced houses, 50m3 for detached or semi-detached
• No extension beyond the plane of the existing roof slope that fronts a highway
• No side-facing windows in walls within 1m of a boundary (obscure glazed and non-opening at lower level permitted)
• Must not overhang the outer face of the wall of the original building

In conservation areas: roof alterations visible from a highway require planning permission.

Permitted development for outbuildings, garages, sheds, and garden offices:

• Must not be forward of the principal elevation or side elevation fronting a highway
• Maximum 4m ridge height for a dual-pitched roof, or 3m for any other type
• In designated areas (conservation areas etc), maximum 2.5m for outbuildings within 2m of a boundary
• Total area of outbuildings must not exceed 50% of the total area of land around the original house (the "curtilage")
• No more than one storey

All PD measurements are taken from the "original house" — the building as it was on 1 July 1948, or as built if built after that date. Extensions built since then do NOT count as part of the original house for PD measurement purposes.

This means if a previous extension has already used up PD depth allowance, further extension may require planning permission even if within the nominal limits. Previous owners may have built extensions under PD that you are unaware of.

Lawful Development Certificate (LDC): You can (and often should) apply for a Lawful Development Certificate from the local planning authority. This is a formal confirmation that your proposed works are lawful under PD rights, or that existing works were lawful at the time they were carried out.

An LDC is not required to carry out works under PD — but it is strongly recommended because:

• It provides certainty that PD applies to your specific case
• It creates a formal record (valuable when selling)
• Lenders and solicitors may require it
• If you are wrong about PD and have no LDC, enforcement action is possible for up to 4 years (for operational development)

LDC applications cost approximately £206 (2025) — a small fraction of the build cost.

Prior Approval: For the larger extensions (up to 6m or 8m) and some other PD classes, you must notify the local authority and obtain prior approval before starting. Starting without prior approval means the work is not lawful under PD, even if it would have been approved.

In conservation areas, additional restrictions apply beyond the Article 4 direction:

• Cladding the exterior of a house in stone, artificial stone, pebble dash, render, timber, plastic, or tiles requires planning permission
• Enlarging or altering a roof requires planning permission if visible from a highway
• Outbuildings, enclosures, and pools in conservation areas have stricter height rules

If you are in a conservation area, assume planning permission is required and check with the local planning authority before any external work.

Assuming your extension is the same as a neighbour's: Conservation areas, Article 4 Directions, and previous PD use can all mean that what your neighbour built without planning permission is not available to you.

Measuring from the current rather than original rear wall: Extensions built by previous owners count against PD limits. If a house was extended 2m under PD in 1990, a terrace can only extend 1m further under current PD limits without Prior Approval.

Ignoring the materials requirement: PD requires materials to be of similar appearance to the existing house. Modern cladding or metal panels may not satisfy this condition, even if the size is within limits.

Not getting a Lawful Development Certificate: Relying on your own assessment of PD without an LDC is risky. Local authorities can take enforcement action if they consider the works to be outside PD — and the burden of proof is on the homeowner.

In London, applying for full planning permission often makes more sense than relying on PD for larger projects because:

• Permission gives certainty and is defensible
• Conservation area design guides give clear guidance on what is acceptable
• Conditions on PD-compliant work (materials, windows) can often be addressed in design without compromising the project
• Planners can be consulted informally before an application is submitted (pre-application advice)

rcbGroup can advise on whether your proposed extension falls within PD or requires planning, and can manage the full planning application process where needed.