Permitted Development vs Planning Permission: A Complete Guide for London Homeowners

Permitted development is a class of development that is automatically granted planning permission by national legislation — the Town and Country Planning (General Permitted Development) (England) Order 2015 (GPDO). It allows certain works to be carried out without the need to apply for planning permission from the local planning authority.

The GPDO is divided into Parts and Classes. Householder works are in Part 1, Class A (extensions), Class B (roof additions), Class C (roof alterations), Class D (porches), Class E (outbuildings), and Class F (hard surfacing). Each Class has its own set of conditions and limitations that must all be met for the works to be permitted development.

If any single condition in the relevant Class is not met, the works fall outside permitted development and a planning application is required. The conditions are not a menu to pick from — all of them must be satisfied simultaneously.

Under Class A of the GPDO, single-storey rear extensions to a house can be built without planning permission if they meet all the following conditions:

• For a detached house: maximum extension depth of 4m from the original rear wall
• For a terraced or semi-detached house: maximum extension depth of 3m from the original rear wall
• Maximum eaves height of 3m if within 2m of the boundary
• Maximum overall height of 4m
• Materials must be of similar appearance to the host building
• No extension forward of the front or side elevation of the original house
• Not on Article 1(5) land (includes National Parks, AONBs, conservation areas) for side extensions
• Combined extensions and outbuildings must not cover more than half the original curtilage

A separate provision — the Prior Approval notification scheme (Class A.1 of Part 1) — allows larger single-storey extensions without full planning permission, subject to neighbour consultation:

Detached houses: up to 8m rear extension depth

Terraced and semi-detached houses: up to 6m rear extension depth

The notification must be submitted to the planning authority, neighbours are consulted for 21 days, and the authority assesses only the impact on the amenity of neighbouring properties. If no objections are received or the authority is satisfied, the extension can proceed. The notification period is 42 days from submission to decision.

Under Class B of the GPDO, loft conversions can be carried out without planning permission if they meet the volume and other conditions:

• Volume limit: 40m³ for terraced houses, 50m³ for detached and semi-detached houses
• No extension beyond the plane of the existing roof slope on the principal (street-facing) elevation
• No addition higher than the highest part of the existing roof
• Materials of similar appearance to the existing house
• Any dormer to be set back at least 20cm from the eaves
• No verandah, balcony, or raised platform
• Not on Article 1(5) land for any addition that is not a rooflight

Permitted development rights are removed or restricted in conservation areas, Areas of Outstanding Natural Beauty, National Parks, and other designated areas. In conservation areas in London — and London has hundreds of them — key permitted development rights are restricted:

In a conservation area, any extension to the side of a house or any outbuilding within the curtilage of a house requires planning permission (Class A rights removed for side extensions on Article 1(5) land). Roof extensions that are visible from a highway require planning permission. Cladding, satellite dishes, and solar panels on street-facing elevations may require permission.

Article 4 directions are made by local planning authorities to remove specific permitted development rights in defined areas where the character of the area would otherwise be harmed. In London, many Article 4 directions remove rights to alter windows, doors, roof materials, and boundary walls in key residential conservation areas. A planning application is then required for works that would otherwise have been permitted development.

The practical consequence: a property in a conservation area or Article 4 direction zone may need a planning application for works that would be entirely automatic in an adjacent street.

A Lawful Development Certificate (LDC) is formal written confirmation from the planning authority that a proposed development is lawful — either because it falls within permitted development or because an existing use or development is established.

An LDC is not required to carry out works that are genuinely within permitted development — the rights apply automatically. But an LDC is strongly advisable when:

• The property is in or near a conservation area where permitted development limits are uncertain
• An Article 4 direction may apply — LDC confirms the position
• Previous works may have used up part of the permitted volume (cumulative additions count)
• A mortgage lender or buyer requires documentary confirmation
• The planning authority has a history of challenging works on similar properties nearby
• The property is listed (LDC confirms listed building consent is or is not required)