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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 are to be set back at least 20cm from the original eaves
The roof enlargement cannot overhang the outer face of the wall of the original house.