SiteRep

Do I need planning permission for a dormer window?

Yes in most cases. A dormer alters the roof profile and the external appearance, and it is not covered by the standard house exemptions, so a planning application is normally required.

Assessment focuses on whether the dormer is subordinate to the roof, how it reads from the public road, and whether it creates overlooking of neighbouring gardens or windows.

Rear dormers are more readily accepted than front ones. Many local authorities publish guidance on acceptable dormer proportions, setbacks from the ridge and eaves, and finishes.

Design factors that help

  • Set back from eaves, ridge and gable ends
  • Width kept well below the roof width
  • Materials matching or complementing the existing roof
  • Obscure glazing or high sills where overlooking is a risk

Sources

Last reviewed 28 August 2026. General information only — not legal or planning advice.

Related questions

← Back to all questions