Civil Engineering Reference
In-Depth Information
Nailing the hip in position
Before fixing the hip in position, hold it in position to ensure that the birdsmouth
checkout is allowing the hip to sit neatly on top of the external wall. If there is a gap
between the back of the birdsmouth and the outside of the corner of the wall it will have
little effect, as long as it is not more than 10 to 15 mm. Fix the top of the hip to the rafters
and the end of the ridge, and then fix it at the birdsmouth checkout using two 75 mm
skew nails into the top of the external wall. Repeat this process for each of the hips.
Cutting and fixing the creepers - the rafters fixed to the hips
The rafters that are fixed to the hips are called creepers. Creepers have a birdsmouth the
same as the common rafters, however the top of the creeper, or plumb cut, will have a 45-
degree undercut so that the face of the plumb cut will sit against the hip for fixing. Use
the roofing boat to mark the face of the creeper, and then with the circular saw set for a
45 degree undercut, cut the plumb cut of the creeper. As you stand below the hip, the
creepers to be fitted to the left of the hip will have a left-hand cut and those on the right
will have a right-hand cut. As you look down on the top edge of a cut creeper, the left-
hand creepers will have the long point at the left side of the creeper (see Figure 8.31).
Figure 8.31
45-degree angle cut at the top of the creepers to enable fixing them to the face of the hip beam
The length of the creepers can either be established mathematically or by physically
measuring them on the job. When measuring them on the job, ensure that the
measurements are taken with the tape parallel to the common rafters. Your building
consultant should be able to supply you with the details on the calculation for the length
of the rafters. This is known as the shortenings of the creepers. It will be a figure that
represents the reduction in the length of each of the creepers from the length of the
