Hi, Our dormer bungalow was built about 50 years ago. There are 4x2 joists running side to side, and 4x2 joists running on top of these front to back tying into the rafters. Internal walls are solid brick. The stairwell has been trimmed from when it was built, and there are windows upstairs already as well, but the previous owners have never gone upstairs. I want to do a en suite bedroom up there I plan on doing it correctly- i.e correct thickness water resistant floor, correct thickness insulation etc. Can it be done without involving the local authority ? bearing in mind we may sell several years from now?