Loft conversion and permitted development rights –most loft conversions can be built within permitted development rights law, meaning you do not need ‘Planning Permission’.
Permitted development – your right to develop your home
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 of the principal elevation that fronts the highway
No extension to be higher than the highest part of the roof
Materials to be similar in appearance to the existing house
No verandas, balconies or raised platforms
Side-facing windows to be obscure-glazed; any opening to be 1.7m above the floor
Roof extensions not to be permitted development in designated areas which include national parks and the Broads, areas of outstanding natural beauty, conservation areas and world heritage sites.
Roof extensions, apart from hip to gable ones, to be set back, as far as practicable, at least 20cm from the original eaves
The roof enlargement cannot overhang the outer face of the wall of the original house
These permitted development allowances apply to houses.
For more help please visit the interactive loft conversions mini guide on the government planning portal