This is general guidance based on standard permitted development rights in England. Rules differ for listed buildings, conservation areas, and properties with Article 4 directions. Always confirm with your local planning authority before starting work.
Do I Need Planning Permission for a Single-Storey Rear Extension in Dorset?
A single-storey extension built to the rear of your home, typically used to enlarge a kitchen, dining room, or living space. One of the most common home improvement projects in the UK.
Planning in Dorset
91%
of planning applications granted
94%
decided within the statutory or agreed time
78%
of householder applications decided within 8 weeks
In the year to December 2025, Dorset decided 2,785 planning applications. 1,235 of these were householder projects such as extensions, loft conversions and outbuildings, of which 94% were granted.
Planning statistics: MHCLG planning application statistics, the year to December 2025. Conservation area and Article 4 data: planning.data.gov.uk, © Historic England / Crown copyright. Open Government Licence v3.0.
Important: Additional Restrictions May Apply in Dorset
Dorset has 310 conservation areas. These include Abbotsbury Conservation Area, Almer Conservation Area, Alton Pancras Conservation Area, Ashmore Conservation Area, Belle Vue Road Conservation Area, Bere Regis Conservation Area. If your property is in a conservation area, some or all permitted development rights may be restricted. For example, you may need planning permission for changes that would normally be permitted, including alterations to the roof, cladding, or extensions visible from a public highway.
Dorset has 77 recorded Article 4 directions. These include Avon Castle & Matchams Park Estate; Bell Hill, Ibberton; Bradford Abbas; Bunkers Hill, Shipton Gorge. Article 4 directions remove specific permitted development rights in defined areas. If your property is covered by an Article 4 direction, you may need planning permission for work that would normally be permitted. Contact Dorset planning department to check whether an Article 4 direction applies to your property.
Check with Dorset planning department before starting work to confirm whether your property is affected by any special designations.
Permitted Development Rules for a Single-Storey Rear Extension
Generally permitted under Part 1, Class A of the GPDO. Standard permitted development allows a maximum projection of 3m (semi-detached or terraced) or 4m (detached). Under the Larger Home Extension scheme (prior approval), this increases to 6m and 8m respectively.
Conditions
- 1Must be to the rear of the original dwelling
- 2Must not extend beyond the rear wall of the original house by more than 3m (semi/terraced) or 4m (detached) under standard PD
- 3Under prior approval (Larger Home Extension), maximum depth increases to 6m (semi/terraced) or 8m (detached)
- 4Materials must be similar in appearance to the existing dwelling
- 5Extension must not be built on land forward of the principal elevation fronting a highway
Size and Dimension Limits
- Maximum height: 4m
- Eaves height: maximum 3m if within 2m of a boundary
- Depth from original rear wall: 3m (semi/terraced) or 4m (detached) under standard PD; 6m or 8m under prior approval
When Permitted Development Does Not Apply
- Must not cover more than half the area of land around the original house (curtilage)
- Does not apply to flats or maisonettes
- Restricted or removed in conservation areas, AONB, National Parks, the Broads, and World Heritage Sites
- Listed building consent required separately for listed buildings
- Article 4 directions may remove these rights locally
What About Building Regulations?
Building regulations approval is likely required
Building Regulations approval is required covering structural stability, foundations, damp proofing, insulation (Part L), ventilation, fire safety, drainage, and electrical work. Building control will inspect at key stages.
Building regulations are separate from planning permission. Even if your project is permitted development, you may still need building regulations approval. Contact Dorset building control or use an approved inspector.
How to Apply in Dorset
If you need planning permission for your single-storey rear extension, you can apply through Dorset's planning department or via the national Planning Portal.
If your project is permitted development and you want written confirmation, you can apply for a Lawful Development Certificate (LDC) from Dorset. This provides proof that your project does not need planning permission, which can be helpful when selling your property.
What Happens If I Build Without Permission?
Building without permission when it is required can result in an enforcement notice from the council, requiring you to alter or demolish the extension. The council has up to 4 years to take enforcement action for building works. Unauthorised extensions can also cause problems when selling your property, as solicitors will check for planning compliance.
Frequently Asked Questions
Do I need planning permission for a single-storey rear extension in Dorset?
Does a single-storey rear extension in Dorset need building regulations?
How do I apply for planning permission in Dorset?
How long does planning permission take in Dorset?
What percentage of planning applications does Dorset approve?
Find a Builder in Dorset
Browse local builders on Tradesfolk. Read reviews, compare quotes, and hire with confidence. 100% free for homeowners, always.