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