Permitted development (PD) rights allow homeowners in England to build certain extensions and alterations without submitting a planning application. The rules are set out in Schedule 2, Part 1 of the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended) and they come with multiple conditions that all have to be satisfied simultaneously. This guide explains the key limits in plain terms.
What Permitted Development Covers
PD rights for house extensions fall under Class A of Schedule 2, Part 1. The rules cover single-storey rear and side extensions, two-storey rear extensions, and roof alterations. Each category has its own dimensional constraints, and all must satisfy the general conditions:
- The extension must not result in more than 50% of the garden area being covered by buildings (including any existing outbuildings)
- The extension must not be forward of the principal elevation or side elevation fronting a highway
- Materials must be of a similar appearance to the existing house
- The property must be a house (not a flat, maisonette, or converted building)
- PD rights are removed on many new-build estates by Article 4 Directions — check your title deeds or call the local planning authority
Single-Storey Rear Extensions: The Core Limits
| House type | Standard PD depth (no application needed) | Larger Home Extension depth (prior approval required) |
|---|---|---|
| Detached house | 4 m | 8 m |
| Semi-detached house | 3 m | 6 m |
| Terraced house | 3 m | 6 m |
Depth is measured from the original rear wall of the house — the wall as it stood when the property was built or as it stood on 1 July 1948 if it pre-dates records. Any previous rear extensions reduce what you can add. If a previous owner already extended 2 m into the garden, you have only 1 m of standard PD left (for a semi-detached), not 3 m.
Additional height constraints:
- Maximum eaves height: 3 m where the extension is within 2 m of any boundary
- Maximum overall height: 4 m (ridge or flat roof top)
- If the extension is within 2 m of the boundary, the height cannot exceed 3 m at any point — this is the most commonly overlooked rule and can significantly restrict a side-return infill or rear extension on a narrow plot
The Larger Home Extension Scheme (Prior Approval)
This scheme, made permanent in 2020, allows single-storey rear extensions up to 8 m (detached) or 6 m (semi/terrace) deep without a full planning application. However, it is not automatic — you must:
- Notify the local authority before starting work
- Include a description of the works, a plan showing the site and the proposed extension footprint, and the contact details of any adjoining owners
- Pay the prior approval fee (currently £120 per application in England as of 2026)
- Wait 42 days for the local authority to consult neighbours and assess any objections
If no objections are raised, or the authority is satisfied that the impact on neighbouring amenity is acceptable, you can proceed. If objections are received and the authority considers the impact unacceptable, it will refuse prior approval and you will need a full planning application.
The scheme does not change the height limits above — a 6 m deep extension still cannot exceed 4 m at the ridge or 3 m at the eaves within 2 m of the boundary.
Side Extensions
Single-storey side extensions are permitted under Class A with different constraints:
- Maximum width: half the width of the original house
- Must not extend forward of the principal elevation
- Must not be within 2 m of the boundary if over 3 m high at the eaves
There is no equivalent of the larger home extension scheme for side extensions — the half-width rule is absolute under PD. A full planning application is needed if you want to exceed it. Importantly, side extensions in a designated Article 4 area (common in conservation areas and many pre-2000 estates) require planning permission regardless of size.
Two-Storey Rear Extensions
Two-storey rear extensions under PD are limited to:
- 3 m depth from the rear wall of the original house
- Must be no closer than 7 m to the rear boundary
- Maximum roof height cannot exceed that of the existing house
- Any upper-floor windows on the side elevation must be obscure-glazed and non-opening below 1.7 m from finished floor level
The 7 m setback from the rear boundary eliminates two-storey PD rights for many terraced properties with short rear gardens.
Corner Plots and Wraparound Extensions
Corner plots face additional restrictions because they have two elevations that face a highway. On a corner plot:
- Side extensions cannot be built on the elevation that fronts a road under PD — they require full planning permission
- A wraparound extension (extending both rear and side) must comply with the side constraints on the road-facing elevation and the depth/height constraints at the rear
In practice, most wraparound extensions on corner plots require a planning application, though the local authority will often be supportive because there is no direct impact on a neighbour’s amenity.
Flats and Maisonettes
Permitted development rights under Schedule 2, Part 1 apply only to houses. Flats and maisonettes have no PD rights for extensions. If you own a ground-floor flat with a garden, any extension — however small — requires a full planning application and very likely the consent of the freeholder and management company as well. Leasehold issues are entirely separate from planning law.
Conservation Areas, Listed Buildings, and Article 4 Directions
Listed buildings: All permitted development rights are removed. Any extension — including those that would be permitted elsewhere — requires both listed building consent and planning permission. SPAB guidance suggests early pre-application discussions with the local authority conservation officer.
Conservation areas: PD rights for side extensions are removed in conservation areas (Schedule 2, Part 1, Class A, Condition A.1(g)). Rear single-storey extensions may still fall under PD, but cladding, roof materials, and chimney works have tighter controls.
Article 4 Directions: Local authorities can withdraw specified PD rights via Article 4 Directions without requiring compensation (if made proactively and justified). These are common on post-war estates, in Areas of Outstanding Natural Beauty, and in some urban infill zones. Check with your local planning authority or search the council’s website for any Article 4 Directions affecting your street.
Checking Before You Build
The safest step before starting any extension is to apply for a Lawful Development Certificate (LDC) from the local planning authority. An LDC costs £120 (householder proposed works) and takes up to 8 weeks, but it provides a legal record confirming that the proposed works are lawful under current PD rights. Without one, you rely on a self-assessment — adequate for most straightforward cases but problematic when selling the property if a solicitor raises questions. An LDC cannot be revoked and transfers with the property.
Many planning consultants offer a PD assessment for £200–£400 — useful on awkward plots or where the dwelling has had previous extensions that eat into the permitted envelope.
