Is a dormer window worthwhile?
It is quite expensive. It doesn’t usually create any extra floor space. All you get is an alcove in the ceiling space. Doesn’t make the roof any higher. Flat roofs sometimes give rise to problems with leaks. Velux windows provide up to 40% more light. Unless the new room is intended for permanent use as a bedroom for an adult, or you wish to create the additional headroom to qualify as habitable accommodation, a dormer window is hardly worth the extra cost. And, of course, you will need planning permission which may, or may not, be granted.
