The base of the rafter roof: position and function

Different forces act on a rafter roof, so the statics must be well planned and the roof adequately fastened. One point that is responsible for the stability of the rafter roof is the base point.

Where is the base point?

The term foot point includes the word foot, so it must be somewhere in the lower area of the roof. It is like that too. The eaves end (lower end) of the rafters rests on a foundation. Often this is the outer wall of the house protruding above the top floor (knee floor). In some cases, the rafters are also directly on the ceiling (this is called jamming). Some rafters end there, others in turn run further out and down and thus form the roof overhang.

  • Also read - The static system of the rafter roof
  • Also read - How does the statics of the rafter roof work?
  • Also read - An important detail of the rafter roof: the verge

No matter how exactly the rafter roof is constructed - the point at which the rafter rests on the foundation is called the base point.

Attachment of the base

A rafter roof is stable because the forces acting on it are absorbed by a stable triangular connection. The base point is an important detail. The rafters have to be fixed there. If this were not done, the roof structure could spread out below, the roof would simply collapse.

There are two options for attaching it to the base. The first is the so-called rafter foot. It is made of metal and connects the wood to the foundation, in this case the ceiling. Rafter feet are available in different designs, as a rigid element, but also with a joint. If the rafters run over a knee stick, so-called cleats are used for fastening. These are triangular timbers that reinforce and hold the rafter at the base. With this construction, the knee stick must not be flat, but must have a threshold in the form of a triangular point, which prevents lugs and rafters from sliding outwards.