Flat roofs use solid wood compound beams connected with nail-plates or some other type of beams – I-beams, laminated timber or Kerto-wood beams, sometimes also nail-plate roof trusses with girders. The choice of beams depends on the width of the spans and the loads exerted on the roof. The flat roof elements have been prepared at the factory in such a way that on the construction site they only require installation and subsequent sealing of the seams.
With flat roofs the load exerted by snow has to be considered as well as the water released by the melting of snow and making sure that rainwater is transported away from the roof. Flat roof elements are designed and produced with the minimum necessary gradients to ensure that water will be transported away from the roof.
Flat roofs are very often also designed with a roof terrace, which sets out extra demands on the structure – the load exerted by the movement of people, trample resistance of the roof covering, the need for additional layers (floor elements for the terrace) and roof terrace barriers as well as the requirements regarding the safe fastening of the above-mentioned structures.
The accompanying image shows a principal solution for a flat roof.