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 Two-Storey Side Extension?
A two-storey extension to the side of your home, significantly increasing floor space on both levels. Subject to strict PD conditions to prevent a 'terracing' effect in residential streets.
The General Position
This project is usually allowed under permitted development rights without needing to apply for planning permission, provided certain conditions and limits are met.
Generally permitted under Part 1, Class A, but with strict conditions designed to prevent properties appearing to merge with neighbours. Must maintain a minimum 1m gap from the side boundary at first-floor level and above.
Conditions and Requirements
- 1Must not exceed half the width of the original house
- 2Must maintain at least 1m from the side boundary at first-floor level
- 3Roof pitch must match the existing house as far as practicable
- 4Materials must be similar in appearance to the existing dwelling
- 5Side-facing upper-floor windows must be obscure glazed and non-opening below 1.7m from the floor
Size and Dimension Limits
- Width: must not exceed half the width of the original dwelling
- Height: must not exceed the height of the existing roof ridge
- Must maintain 1m gap from side boundary at first floor and above
When Permitted Development Does Not Apply
- Must not cover more than half the curtilage
- Does not apply in front of the principal elevation
- Not permitted development in conservation areas, AONB, National Parks, the Broads, or World Heritage Sites
- Does not apply to flats or maisonettes
What About Building Regulations?
Full Building Regulations approval needed covering structural integrity, foundations, thermal performance, fire safety and escape routes, sound insulation between floors, ventilation, drainage, and electrical work.
Building regulations are separate from planning permission. You may need both, one, or neither depending on your project. Building regulations cover the safety and quality of building work, including structural integrity, fire safety, insulation, ventilation, and drainage.
How to Apply for Planning Permission
Check if you need permission
Review the permitted development rules above. If in doubt, contact your council or apply for a Lawful Development Certificate.
Prepare your application
You will need scaled drawings, a site plan, and a completed application form. An architect or planning consultant can help with this.
Submit to your local council
Applications can be submitted online via the Planning Portal or directly to your council. Select your council below for a direct link.
Wait for a decision
8 weeks for householder planning applications..
Application cost: £258.
What Happens If I Build Without Permission?
Enforcement can require demolition of the upper floor or the entire extension. Two-storey side extensions that create a terracing effect are particularly likely to attract enforcement. Solicitors routinely flag these during property sales.
Find a Builder for Your Two-Storey Side Extension
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Select Your Council
Choose your local council for guidance specific to your area, including links to apply and whether your council has conservation areas or Article 4 directions that could affect your project.
London
South East
South West
East of England
East Midlands
West Midlands
North East
North West
Yorkshire and the Humber
CA = has conservation areas. A4 = has Article 4 directions. These may restrict your permitted development rights.