How can you calculate rafters?

The cross-section and the length of the rafters depend on the one hand on the inclination of the roof and on the other from the roofing. But there are other factors in an exact calculation of the rafters into it.

Cross-section of rafters

Even if the exact calculation, taking all the important points for a dwelling house into account, can not and does not itself, one should know approximately what is involved when rafters are calculated.

The cross-section of the rafters depends in part on how much weight should later weigh on the roof. Then the inclination of the roof must be included as well as the question, in which height the purlins are attached, which intercept the rafters.

What is important in the calculation?

Here is a small overview of the aspects to consider, which are important for a calculation of the rafters. But you should always remember that even for a carport a verifiable statics must be present.

  • roof pitch
  • distance of the purlins to the ground and to the ridge
  • weight of the roofing
  • snow load (the average amount of snow in Central Europe is required)
  • possibly the weight of a solar system
  • wood quality

Which wood is used?

A naturally grown softwood, for example, does not carry as much weight as a BSH gluelam, even if it can also be made of coniferous wood. Therefore, this aspect must also be included in the calculations of the rafters.

Glulam glulam is a glued laminated timber, which is first dried as well as laminated beams in individual parts. Only after drying, this beam is made with glue and great pressure from the individual parts.

Tips & TricksIf a rafter size comes out in the calculations, which is approximately between two common cross sections, you should always choose the stronger cross section. However, you may also have to consider the weight of the stronger rafters.
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