A roof may very well be the most vital part of a structure. A roof protects it from the elements, which can take their toll on a building. There are beautifully crafted roofs of impressive appearance, but the unseen parts underneath -- the roof frame -- are an important part of a roof structure.
One of the main parts of a roof frame is the rafters. Rafters comprise the main framework of a roof; rafters are to roofs what joists are to the floor of a building or what studs are to a wall. Rafters extend at an angle from the top wall plate to form the top of a house. The rafters rest on and are nailed to the top wall plate, and are joined together at the top in one of several methods, depending on the type of roof. The decking of the roof is nailed on top of the rafters, providing a base for the roof surface.
In some situations, a builder will use a roof truss in lieu of rafters. A truss is a prefabricated structure that is used in instances when the distance that needs to be spanned is too long for single rafters. A roof truss is also known as a rafter truss assembly, due to the fact that a truss is actually a set of rafters that are joined together by metal plates and pieces of plywood known as gusset plates and are supported by members known as webs that support the cords (the rafter part of the truss).
An important part of a roof frame is the wall plate. The wall plate is the board that is laid on top of the wall structure. This part is important to roofs since it is the part of the frame that the rafters or roof trusses will be affixed to.
Dormers are an architectural option for a roof. The dormer is a framework of members that are either gabled (with an angled top) or shed-type (with a flat top) and that stand out on the roof usually encasing a window. A dormer adds visual interest to a plain roof.