A hip rafter truss is the assembly of timber members that supports the hip rafter — the sloping arris that runs upward from the eaves to the ridge where two roof planes meet at an external angle. You find it on a hipped roof, a pyramidal roof and on roof extensions where one sloping roof plane joins another.
How it works
The hip rafter is the heaviest sloping timber of the roof: onto it rest the short jack rafters of both adjoining roof planes. Because the load of two roof planes comes together on this arris, the hip rafter is sized more heavily than an ordinary common rafter. At the bottom the hip rafter bears on the wall plate or on a trimmed opening; at the top it meets the ridge or a strutting truss.
Application
- Hipped roof and pyramidal roof — where the roof planes meet at the corner of the building
- Dormers and extensions with a hipped or angled roof plane
- Restoration — on historic roofs the hip rafter often has to be fitted to size with mortise-and-tenon or notched joints
The contractor should pay attention to a good bearing and to sealing the valley rafter (the reversed, internal variant): it is precisely along these sloping lines that leaks otherwise occur.
Related terms
- Hip rafter
- Rafter
- Valley rafter
- Truss
- Roof structure
- Hipped roof
- Ridge
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.