Taking the Sag Out of Shed Dormers

The shed dormer remains a popular remodeling project because it is such a simple and inexpensive way to enlarge a too-small house. But frequently shed dormers are retrofitted without proper concern for whether or not the structure can handle the new and different loads being introduced. In this article, I’ll examine some of the structural concerns that must be considered before retrofitting a shed dormer to an existing roof. Of course, the same concerns and recommendations apply equally to new construction as well. Shed Dormer Basics Consider a basic frame roof, like the one in Figure 1. Assuming its members are correctly sized, this roof is a rigid triangle. The rafters lean against each other at the ridge with a force equal to