B.1 Development not permitted
Development is not permitted by Class B if—
(a)any part of the dwellinghouse would, as a result of the works, exceed the height of the highest part of the existing roof;
(b)any part of the dwellinghouse would, as a result of the works, extend beyond the plane of any existing roof slope which fronts any highway;
(c)it would increase the cubic content of the dwellinghouse by more than 40 cubic metres, in the case of a terrace house, or 50 cubic metres in any other case;
(d)the cubic content of the resulting building would exceed the cubic content of the original dwellinghouse—
(i)in the case of a terrace house by more than 50 cubic metres or 10%, whichever is the greater,
(ii)in any other case, by more than 70 cubic metres or 15%, whichever is the greater, or
(iii)in any case, by more than 115 cubic metres; or
(e)the dwellinghouse is on article 1(5) land.