Monday, April 30, 2007

Framing A Hip Roof

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 Roof Framer". Not only does it contain all the necessary rafter tables, but also the secrets to cutting a roof. 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

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.

Mike Merisko (C)2007