New roof lights or skylights will not normally require an application for planning permission providing:
However, if additional volume is created it may be treated as an extension and separate rules will apply.
If you live in a listed building or designated area (conservation area, national park, area of outstanding natural beauty, etc…) you should check with your Local Planning Authority before carrying out any work.
Details taken from: https://interactive.planningportal.co.uk/terraced-house/outside-terraced-house/roof-window
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