The short answer
Most single-storey rear extensions to a house in England do not need a planning application — they fall under Permitted Development Rights (PDR). However, PDR has strict limits, and if your extension exceeds them in any way, a full planning application is required.
Permitted Development rights do not apply if:
- Your property is in a Conservation Area, National Park, AONB, or World Heritage Site
- Your property has had PDR removed by an Article 4 Direction
- The property is a flat, maisonette, or listed building
- You have already used your PDR allowance through previous extensions
Permitted Development limits for rear extensions in England (2026)
Under the Town and Country Planning (General Permitted Development) (England) Order 2015 (as amended), a single-storey rear extension is permitted without planning permission if it meets all of the following:
| Condition | Detached house | Semi-detached or terraced |
|---|---|---|
| Maximum depth (from original rear wall) | 4 metres | 3 metres |
| Maximum height at eaves | 3 metres | 3 metres |
| Maximum overall height | 4 metres | 4 metres |
| Materials | Similar appearance to existing house | Similar appearance to existing house |
| No verandas, balconies, or raised platforms | Required | Required |
| No side elevation facing a highway | Required | Required |
Larger Home Extension Scheme: Under a prior approval notification process, you can extend up to 8 metres (detached) or 6 metres (semi/terraced) in depth. This requires a Prior Approval application to your Local Planning Authority (LPA), and neighbouring properties must be notified. The LPA then has 42 days to object.
When you will always need planning permission
You will need a full planning application if any of the following apply:
Property type exceptions:
- Flats and maisonettes — no PDR at all
- Listed buildings — require listed building consent in addition to any planning permission
- Properties where PDR has been removed (check via local planning authority or Land Registry)
Design exceptions:
- The extension wraps around the side of the house and creates a side extension element
- The extension includes a raised platform, balcony, or veranda
- The extension height exceeds PDR limits
- Materials differ significantly from the existing house
Location exceptions:
- Conservation Areas (no rear extensions visible from the highway without permission)
- National Parks, AONBs, and World Heritage Sites
- Areas subject to Article 4 Directions
What about double-storey rear extensions?
A two-storey rear extension is permitted without planning permission only if:
- It does not extend beyond 3 metres of the original rear wall
- The roof pitch matches the main house as far as practicable
- There are no windows in any wall or roof slope within 1 metre of a boundary
- The eaves and ridge height do not exceed the existing house
- It is more than 7 metres from any boundary opposite the rear wall
In practice, very few double-storey rear extensions meet all these conditions. Most require planning permission.
Building Regulations: separate from planning
Planning permission and Building Regulations are two separate systems. Even if your extension does not require planning permission, it will almost certainly require Building Regulations approval.
Building Regulations cover:
- Structural integrity (foundations, steelwork, floor and roof structure)
- Thermal performance (insulation standards — Part L)
- Fire safety (escape routes, fire doors)
- Ventilation (Part F)
- Damp proofing (Part C)
- Electrical work (Part P)
- Drainage (Part H)
Building Regulations approval is obtained either via your Local Authority Building Control (LABC) or a private Approved Inspector. Your contractor should assist with this or advise you on how to proceed.
Party Wall Act: a third separate requirement
If your extension involves:
- Excavation within 3 metres of a neighbouring building's foundations
- Building on or near the boundary with an adjoining property
- Any work to a shared (party) wall
...then the Party Wall etc. Act 1996 may apply. This requires you to serve a Party Wall Notice on your neighbours and, if they do not agree in writing, appoint a surveyor to manage the process.
Party Wall matters are separate from both planning and building regulations. They are a civil matter between property owners and are not processed by the council.
How to check if your extension needs planning permission
1. Check your property's planning history at your Local Planning Authority's online portal
2. Identify whether an Article 4 Direction applies — ask your LPA or check their website
3. Measure the proposed extension against the PDR criteria above
4. If in doubt, submit a Lawful Development Certificate (LDC) application — this is a formal confirmation from the LPA that your extension is lawful under PDR. Cost: £258 in England (2026). Turnaround: typically 8 weeks.
An LDC is strongly recommended for any extension you plan to sell the property after — it protects against future queries from buyers' solicitors.
Summary
| Extension type | Usually needs planning? |
|---|---|
| Single-storey rear (within PDR limits) | No — PDR applies |
| Larger single-storey rear (Prior Approval) | Prior Approval notice required |
| Single-storey rear in Conservation Area | Yes |
| Double-storey rear | Usually yes |
| Side extension | Depends on size — check PDR rules |
| Extension to a flat | Yes — no PDR for flats |
| Listed building | Yes — plus listed building consent |
When in doubt, apply for a Lawful Development Certificate or consult your LPA's pre-application advice service before committing to a design.