The Roof Framework
The roof framework should be able to support itself and the roof covering. Additionally, the roof structure has to resist the pressure of wind and snow. The roof framework has to be anchored to the masonry, so that the wind cannot lift the roof or blow it away.
For that purpose the rafters are joined to the beams or purlins with nails or metal bonders. The beams and the purlins are then fixed with embedded anchor bolts, flat steel link plates or mounting brackets on the substructure. The most important types are the rafter roof, the collar beam roof and the purlin roof.
The roof framework in any case consists of rafters and roof battens. The cross section of the battens should be chosen according to the distance between the rafters (DIN 4074). Up to a distance of 1 m between the rafters a batten cross section of 40/60 mm is sufficient. Generally, the distance between the battens depends on the roof pitch, the wind suction force of the roofing and the type of reed used.
Very commonly the distance between the two lower battens (at the eaves) measures 10 cm, whereas the distance between the bearing edge of the roof covering and the first batten and between the first and the second roof batten should not exceed 20 cm.
As the reed bundles should be fixed with two ties, when
short reed is employed, the distance between the battens has to be smaller than when using long reed. For a roof pitch of up to 60° the distance between the roof battens should not exceed 0.35 m. If the roof pitch is higher than 60° the distance between the battens should not exceed 0.3 m.
It is important that roof has a pitch of at least 45° (according to
Rules for Reed Thatching).
