There are two ways to design a hip in traditional French timber framing:
- “L’arêtier sur lierne”
- “L’arêtier sur tasseaux”
I didn’t find any translation for those words.
What they have in common: the sides are plumb, backing cuts (or not) and the principal hip rafter can be thicker than the hip rafter.
“L’arêtier sur lierne”
In French, “une lierne” is an element, often of small size, set against another element.
In this case, the hip rafter is set above the principal hip rafter.
The jack rafters are set against the hip rafter.
The purlins are set against the principal rafter.
Following the chosen wood sections, there can have a claw to the purlin.
Depending on the chosen wood sections of the hip jack rafters and the purlins, the rafter can be designed with one single piece of wood.
“L’arêtier sur tasseaux”
In this case, the hip rafter and the principal hip rafter are separated: the purlins come between these two elements, unlike in the previous case.
The hip jack rafters are set against the hip rafter (and can sometimes have a claw).
The purlins are set on the principal hip rafter, they can’t have a claw but need to be cut at the top, to give a support to the hip rafter.
The top face of the principal hip rafter need to be notched to let the passage of the purlins.
A cleat has to be set on the principal hip rafter to avoid the rotation of the purlins.
Sometimes the support is not wide enough for the hip rafter, in this case the best way is to do “un chevron d’arêtier chanlatté” (translation?).
It’s a rotated hip rafter, composed in two pieces aligned with the top of the roof and supported by the purlins.
In this case the hip jack rafters do not have plumb cuts but square cuts.