Loft conversion planning permission under permitted development

Planning permission is required where you extend or alter the roof space and it exceeds specified limits.

There are different rules for “any alteration to the roof of a dwelling house

A loft conversion for your house is considered to be permitted development, not requiring an application for planning permission, subject to the following limits and conditions:

  • A volume allowance of 40 cubic metres additional roof space for terraced houses
  • A volume allowance of 50 cubic metres additional roof space for detached and semi-detached houses
  • No extension beyond the plane of the existing roof slope. No extension to be higher than the highest part of the roof
  • Materials to be match in appearance to the existing house
  • You can’t have verandas, balconies or raised platforms
  • Side-facing windows to be obscure-glazed and also any opening to be 1.7m above the floor
  • Roof extensions not to be permitted development in listed or conservation areas
  • Roof extensions, apart from hip to gable ones, to be set back, as far as practicable, at least 20cm from the original eaves and some area has to be 50cm from the original eaves.
  • The roof enlargement cannot overhang the outer face of the wall of the original house.

Any previous roof space additions must be included within the volume allowances. Although you may not have created additional space a previous owner may have done so.

The permitted development allowances described here apply to houses and not to:

  • Maisonettes & flats
  • Other buildings
  • Converted houses or houses created through the permitted development rights to change use
  • Areas where there may be a planning condition, Article 4 Direction or other restriction that limits permitted development rights.


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