Planning
Planning permission for house extensions
The first question, and the one that decides everything else. Many extensions need no planning application at all — but the limits are specific, and they are not the same for a terrace, a semi and a detached house.
Of the homeowners who told our quote tool where they were up to over the last 90 days, around a quarter did not know whether they needed planning permission, and most had no drawings yet. If that is you, nothing here assumes prior knowledge.
Start with these
- Do I need planning permission?
- Building Regulations
- Larger home extension route
- Lawful development certificate
- Party wall agreements
- Drawings and who draws them
- Conservation area extensions
- Extending a listed building
- How long does it take?
- Refused? Appeal or resubmit
- Building over a drain or sewer
- Height limits & the 45 degree rule
- When neighbours object
- Extending a leasehold house
Get quotes from extension builders near you
Tell us what you are planning and we will match you with up to three builders who cover your area. Free, no obligation, and you choose whether to go ahead.
Get free quotesWritten and checked by the HouseExtensionExpert editorial team · Last updated: 31 August 2026 · Planning and Building Regulations points are checked against current Planning Portal and GOV.UK guidance; cost ranges come from BestBuilders’ 2026 regional cost model (published national cost guides × a regional labour index, averaged across 519 UK towns). Ranges are indicative, not quotes.Spotted something out of date? Tell us.