Oak trusses are a connection where a few rafters together with the ridge beam of a wooden ceiling create a three-element truss attached to the outer building walls. Beams that create a wooden ceiling can be attached straight to the wall or on the wall. Rafters leaning against the wall are connected in the roof ridge and are attached to the roof crown. In this case, truss consists of only two elements, and therefore the function of the third side of the triangle must be taken over by the ceiling (for example reinforced concrete or prefabricated).
Oak trusses, rafters and purlins are most often planned in family houses. On more complicated roofs, the structure is a result of many variants. Sorting individual elements such as the cross-sections are the results of the strength calculations which take into account the building dimensions, its location (and accordingly the snow and wind load zone depending on it), the angle of inclination, the arrangement and dimensions of skylights and the type of roofing.
Rafters – the simplest type of the rafter construction. It is used if the span of the roof is less than 7 m, the inclination is 30-50°. For light roofing, the length of rafters should be 4,5 or 5 m. Oak trusses have only two supporting points – in the roof ridge or on the wall, laid on the ceiling or on the knee wall.
Grooved rafters – made on roofs with a span of 7-11 m and an inclination of 35-60°. In this solution, the rafters are additionally reinforced by horizontal grooves that are attached to the middle of the rafter or slightly above their half (around ⅓ of the distance from the roof ridge). If this construction is used in houses with a residential attic, they can serve as ceiling beams above its room.
The strength and stability of the roof structure depends on the correct performance of the carpentry work. The installation on site should be done relatively quickly. Long elements tend to change linearity if they are not assembled quickly. Oak trusses will be resistant to water, wind and snow. Oak beams must be of high quality to carry several tons of load.
Before ordering, it is necessary to prepare all pieces of oak wood needed – the number and the length of elements and their cross-sections. They must not have unnecessary cut outs, notches or holes that were not agreed on with the building manager or superior. All components must fit well during assembly. There must be no gaps greater than 5 mm or cracks between the joints. The elements are interconnected only at points provided by the designer.
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