Timber roof truss

The roof is the load-bearing part of a roof, its supporting structure. The wooden roof, it is the overall structure, which is necessary for supporting the rafter. Roof trusses are usually wood construction (and then built by carpenters ) and mostly covered by roofers.

Word origin, materials used, use of the term

The word is in German occupied since the 16th century, the word ' chair ' here means " frame ", especially one on which something else rests. So far as the roof truss is considered a " frame on which rests the roof is attached ", as a " carrying the roof skin [ wood ] Construction ".

With truss roof constructions can be addressed from different materials. Often, components and structures made of wood are meant. The term is - even technical language - focus today and for different situations used: With truss can be addressed in the broadest sense, the entire wooden roof structure. In a narrower sense, the wooden roof truss does not carry the roof, but the roof rafters, which are thus not expected even to the roof. The roof is the totality of the rafters supporting wooden structures, which transfer loads from the roof surface to bottom. In particular parallel to the ridge of a rafter roof and Pfettendächern arranged supporting structure can be raised, forming a longitudinal association.

Technical terms in the roof

With a wooden roof (in the narrow sense) the supports or stems are also referred to as a chair or stool post columns. A number of them together with thresholds, Rähmen and braces have a parallel to the first longitudinal standing association, the chair wall. The threshold for load distribution under seat post is also called chair threshold.

A standing chair is a chair with vertical roof pillars chair. If these are arranged in a single chair wall (which then usually located in the middle, under the First ), is spoken by just standing chair, at a symmetric two-sided position of the double stationary chair. Combined constructions are also referred to as a multi- standing chair.

When lying chair the chair pillars are slanted, her foot is in the vicinity of the outer walls. One advantage of this arrangement is in a better usability of the column-free roof space. The lying chair charged the underlying floor joists on the edge, near of the support, and not in the center of the field. This provides a lower bending moment. This static situation was more favorable in historic buildings particularly significant when the ceiling beams had to make do without intermediate support. This was the case when in the basement under the floor joists large column-free spaces should arise, for example, the nave of a church.

The collar beam of a collar beam roof can be supported by chair post. If this happens in the middle, creating a simple stationary chair below the collar beam. The horizontal bar above the seat post and below the collar beam is called Stuhlpfette or Stuhlwandpfette. Previously at great length of the collar beam, two Stuhlpfetten were used as double- stationary chair. Here were the chairs not only the load transfer from the collar beam, but were simultaneously used for longitudinal reinforcement of the roof. Such Stuhlpfette is also called Stuhlrähm.


Roof of the granary floor in front of the castle Castle Mild stone. The base 1394/95 made ​​of pine wood is one of the largest and best preserved medieval roof trusses in Germany.

Roof forms. Overview from Meyers encyclopedia, 4th Edition 1885-90.

Implementation in the Cathedral of St. Blaise