Existing loft conversion, do I still have allowance for permitted development?

26 Mar 2021
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United Kingdom
Hi, i'm looking for advice as cant seem to find the answer easily. I know I have permitted development for doing a single storey 3m extension at the back of our detached house and can even make it far bigger if we wanted. However we did a loft conversion 2 years ago, and seem to remember that this takes some of your permitted development allowance away?

Can anyone advise if this is true?

Many thanks

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Yes you have a set permitted amount of new roof volume, so it impacts on new roof volume or dormer volume and is cumulative.
@ Woods: I'd disagree there;
there are appeal cases on Planning Jungle in which inspectors have determined that a roof enlargement under class B (eg dormer) is separate from the roof of a class A extension (assuming the dormer and the roof of the extension are not in physical contact).

(If the roof enlargements join, which they might do with a side extension or an extension to a bungalow, then 50m³ is the limit for both combined)

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