Shed roof: the shed roof or shed dormer has an unfortunate name, but when artfully built, proves a cost effective roof frame for an addition, as well as an attractive one. starting again with that inverted �v,� the shed-style addition roof is a flat plane say the shape of a floor tile or square cracker that meets one �leg� of the upside. Dormers. adding one or more dormer windows to a gable roof is an age-old way of adding living space to cramped quarters. "building up" or "finishing the attic" is what it's often called.. This step by step woodworking project is about 8