A Dutch truss is a long-established timber roof truss in which the roof planes (the rafters or decking beams) transfer their load through struts and a collar beam onto a cross beam — the tie beam or main beam — which rests on the wall plates. It is one of the classic truss forms in Dutch roof construction, alongside among others the English truss and the purlin roof.
Structure
A Dutch truss essentially consists of:
- Two principal rafters that follow the shape of the roof plane
- A collar beam (cross connection high in the truss) that holds the principal rafters together
- Struts that carry the forces diagonally to the tie beam
- A tie beam at the bottom that takes up the horizontal thrust, so that the walls are not pushed outward
The parts are traditionally joined together with mortise-and-tenon joints and wooden dowels.
Application
The Dutch truss was and is used in dwellings, farmhouses and warehouses with a gable roof. Because the tie beam absorbs the thrust, the roof can rest on relatively light walls. When converting or using the attic, it is important not to simply saw through the tie beam and the collar beam: they are essential for the stability of the roof.
Related terms
- Truss
- Roof structure
- Collar beam
- Tie beam
- Wall plate
- Gable roof
- Purlin
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