The Town and Country Planning (General Permitted Development) (England) Order 2015 No. 596

SCHEDULE 2 E+W Permitted development rights

PART 1 E+W Development within the curtilage of a dwellinghouse

Class B – additions etc to the roof of a dwellinghouse E+W

Interpretation of Class B E+W

B.3  For the purposes of Class B, “ resulting roof space” means the roof space as enlarged, taking into account any enlargement to the original roof space, whether permitted by this Class or not.