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The hip jack rafter can be thought of as the lower end of what type of rafter?
- Common rafter
- It is on the same slope, on the same on-centre layout and has an identical birdsmouth
- The tail is calculated, shortened and cut in the same manner as the common rafter.
Hip jack rafters are spaced 400mm on-centre. Moving towards the corner of the building, how much shorter is the run of each hip jack?
the run of each hip jack would be 400 mm shorter than the previous one
The run of a hip jack rafter is equal to its distance from the _______
For laying out the hip jacks, you should use the framing square set up for ___________
- the common rafters
- Because the hip jack is parallel to the common rafters, use the same unit rise and unit run numbers as the common rafters
What is the shortening for the upper end of a hip jack rafter?
1/2 the diagonal thickness of the hip rafter
What is the shortening for the lower end of a hip jack rafter?
Full thickness of the fascia
What type of cut is required for the upper end of a hip jack rafter?
Single cheek cut
How is the ridge line length determined for a hip roof?
Building length - building width
What must be done to the line length of the ridge to find the actual length?
Add 1/2 thickness of a common rafter to each end
Which rafters are laid out first for a hip roof?
- Pin rafters and first common rafters
- Ensure that the distance from their centres to the building corners is equal to half the width of the building.
What is a concern when fastening hip jacks tot eh sides of a hip rafter?
- Ensure that the hip jacks are installed accurately, as opposing pairs on each hip, so that they do not push the hip rafter out of alignment.
- Stretch a string line down the length of the hip to help keep it straight.