One of the first questions homeowners in Somerset ask us is "will I need planning permission for my extension?" The good news is that many extensions can be built under Permitted Development rights — meaning no planning application, no planning fees, and no waiting 8–13 weeks for a decision. Here is a clear, plain-English guide to the rules that apply in Somerset.
What is Permitted Development?
Permitted Development (PD) rights are a set of rules that allow certain types of building work to be carried out without needing to apply for planning permission. They are set nationally by the government but local councils can remove or restrict them in certain areas.
When Can You Build an Extension Without Planning Permission in Somerset?
For a single storey rear extension on a house, you do not need planning permission if all of the following apply:
- The extension does not exceed 4 metres in depth (detached house) or 3 metres (semi-detached or terraced)
- The extension is not higher than 4 metres at the ridge
- The extension does not exceed the height of the original house at the eaves
- The extension does not take up more than 50% of the total garden area
- Materials match or are similar in appearance to the original house
- The house has not already used up its PD allowance with previous extensions
- The house is not in an Article 4 Direction area
- The house is not listed
Note:Under the Larger Home Extension scheme you can extend up to 8 metres (detached) or 6 metres (semi/terrace) under Prior Approval — this requires notifying the council but is not a full planning application.
When Do You Need Planning Permission for an Extension in Somerset?
- The extension is two storeys — always requires planning permission
- The property is in a Conservation Area or Area of Outstanding Natural Beauty (AONB) — Somerset has significant AONB coverage
- The property is listed — any extension to a listed building requires Listed Building Consent
- The extension would be visible from a public highway (in some cases)
- Your local council has an Article 4 Direction removing PD rights in your area
- The extension would be on a flat
- You want to extend forward of the principal elevation
- The extension is commercial or mixed-use
Areas in Somerset Where PD Rights May Be Restricted
If your property is in any of the following, your permitted development rights may be reduced or removed:
- Blackdown Hills AONB
- Mendip Hills AONB
- Cranborne Chase AONB
- Any Conservation Area — check with Somerset Council or your local planning authority
- National Landscape designations
- Any settlement with an Article 4 Direction — your solicitor should have noted this on purchase
Does Permitted Development Still Need Building Regulations?
Yes — almost always. Even if your extension does not need planning permission, it almost certainly needs Building Regulations approval. This is separate from planning and covers structural integrity, fire safety, insulation, ventilation, drainage and electrical work. We submit Building Regulations applications on your behalf as part of our service.
How to Check if You Need Planning Permission
The most reliable options are:
- 1Check the Planning Portal interactive guide at planningportal.co.uk — it gives a yes/no answer for common extension types
- 2Submit a Pre-Application Enquiry to Somerset Council (costs around £100–£200) for a written opinion
- 3Apply for a Lawful Development Certificate (LDC) — this gives you legal certainty that your extension is permitted development. Costs around £250 in fees. We strongly recommend this
- 4Ask us — as part of a free site visit we will give you our honest assessment of whether planning is likely to be needed
Book a free planning advice visit
Free site visit — no obligation
What Happens if You Build Without the Right Permission?
Building without planning permission when it is required is a serious issue. The council can issue an Enforcement Notice requiring you to demolish or alter the work. This can be devastating — especially as it will appear on searches when you try to sell. Always check first. We have seen homeowners in Somerset face very expensive rectification works because they did not verify PD rights before building.