Do you need planning permission for a loft conversion with dormer?

I’ve seen mixed advice online and I’m a bit confused. How do I know if a dormer loft conversion needs planning permission or not? Don't want to start serious conversations with builders before I'm clear on this and a few other things

Asked by Patrick on 31st Jan 2026
Expert Trade Answers
"It depends on a number of different factors Partrick, size, spec, materials used, position of the dorma, your location ect. You can get more information from your local councils planning website or speak to a specialist about what you want to achieve and they should be able to advise you correctly."
Answered on 31st Jan 2026 - Member since Jan 2026 - report
"I think it comes under permitted devolopment. Because u are changing the outside of the property. Will still need plans. Drawn up. If u need a steel put in then yes. Full planning and structual engineer"
Answered on 31st Jan 2026 - Member since Nov 2025 - report
"Yes you fo need planning permission, and before you get a builder its best to get architectural, and structural plans for them to be able to give you the best estimated quotation on materials that are specifically required for your project."
Answered on 31st Jan 2026 - Member since Apr 2023 - report
"Hi Patrick we do a lot of lift conversion around Sheffield and as a rule if you just have velux it’s no but when a dormer is fitted it is altering the roof structure and going out so more often than not they want planning different areas have different rules but that’s what we find Aron Sheffield hope this helps if you require anything else just let me know cheers"
Answered on 31st Jan 2026 - Member since Jun 2024 - report
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