One of the two most popular roof designs, if not the most popular is the hip roof. Not only
does it add architectural lines to the design of a house, but it also offers more protection
from the elements to walls, windows, and doors, when framed with a generous overhang. It
also lends more to the structural integrity of a home with its rafters tying off to all four
corners and walls of the structure.
A hip roof is a little more complex to frame than a gable roof. Besides a ridge board, a
gable roof has only common rafters (all rafters the same length) as its only components. The
components of a hip roof are the ridge board, common rafters, hip rafters, and jack rafters.
The hip roof does not always have a ridge board. If the building is a square with all four
walls being the same length, there will be no ridge and the roof will resemble a pyramid.
When cutting the common, hip and jack rafters, their lengths can be determined by using a
calculator or a rafter table book like “The Full Length Rafter Framer”. the length of the
ridge can be determined by subtracting the width of the building from its length. For
example, if the building is 30 x 24, the ridge will be 6 feet in length. If the ridge board
is 1 1/2″ thick (which is usually the case), then 1 1/2″ needs to be added to the ridge
length. This is because all common rafters are shortened half the thickness of the ridge or
3/4″. This allows the top of the common rafters to line up with the top of the ridge at each
end.
When framing a hip roof, always start with the common rafters. This will place the ridge in
its proper location. This part of the roof is framed like a gable roof, but the similarity
ends there.
Start by nailing common rafters on one side of the ridge at each end. Now raise the ridge
and nail two rafters on the other side of the ridge opposite the first two rafters. Once
this is done, push the ridge up so the birdsmouth cuts pull in tight to the walls on each
side of the building. These rafters can now be nailed to the wall in their corresponding
locations in relation to the ridge. Now nail the two common rafters to the center of the end
walls and to the ends of the ridge board. This will lock the ridge in its exact location.
The rest of the common rafters can be nailed to the wall and ridge board.
The next parts to be installed are the four hip rafters. These are nailed on the outside
corners of the buildings walls and in the intersection made by the end and first common
rafter where they meet at the ridge. With the hips and common rafters in place, its easy to
see why this makes for such a strong and solid roof.
With the hip rafters in place the jack rafters can be installed. Before nailing on the first
jack rafter, a string must be run from the plumb cut on the hip rafter to just above the
birdsmouth. This can be done by driving a nail in the center of the hip at the above mentioned
locations. Tie the string to one nail, pull it tight, and secure it to the other nail. This
is to ensure the hip rafter stays straight during the jack rafter installation. As the jacks
are nailed on, the string should be kept at the center of the hip. To help keep the hip
rafter straight, the jack rafters should be nailed on in pairs, first one side of the hip,
then its mate on the other. This process is continued all the way down the the hip rafter
till all jack rafters are installed on both sides of the hip. Remove the string and repeat
this procedure on the remaining three hip rafters to complete the framing of the roof.
Collar ties and fascia boards will need to be installed before the roof can be sheathed, but
these are the basic steps to framing a hip roof.
