Hip Roof Load Path

Understanding the load path.

Hip roof load path. Some of that load will be transferred down to wall at the bottom of the hip rafter and some to the ridge the hip is definitely carrying a load and so is the ridge now that its a hip roof it is carrying what has been transferred by the hip rafter. The continuous load path from the roof to the foundation has to resist uplift pressure that can rip roofs away from walls shear forces in the walls that brace the building sliding forces that tend to push the house off the foundation and overturning forces that tend to tip the house. In the above example the supplier specified a humongous beam that did not appear justified. Loads are contributed.

A uniform loadis a continuous load along the entire length of a member and is expressed in plf. 20 psf x 6ft 120 pounds per lineal foot. Again this house has the same width dimension but it has 2 levels. There are no gable ends on a building with a hip roof.

Horizontal load path as the roof load pushes downward vertically the rafters tend to spread outward at their lower ends pushing against the walls of the house. A hip roof is a roof in which the roof slopes upward from all four exterior walls to meet at a central ridge. A partial uniform loadis also expressed in plf but does not run the entire length of the member. Dropping a hip lowers the heel of the hip rafters while backing a hip involves beveling the top edges of the hip rafters.

To what extent do the opposing forces of a symmetrical hip roof system relieve the point load resulting from a roof brace. Hip rafters must be dropped or backed so that the edges of the rafter won t interfere with the roof sheathing. 1020 pounds per lineal foot. The forces on the hip rafter jack rafter connection consist of the tributary roof load transfered by the jack rafter plus a force along the axis of the jack rafter which also changes the perspective of the stresses at the bottom of the jacks from straight down to sliding off the plate.

16 inches 12 1 333 ft. 10 psf x 6ft 60 pounds per lineal foot. In hip roof designs all four exterior walls support the ends of roof rafters so all exterior walls bear a weight load from the roof above them. Its not just a frieze block anymore its holding up some weight.

If hips are self supporting why are braces required.