Rafters - the usual dimensions


Rafters are beams that are used to build a roof truss. They have to carry heavy loads, especially when heavy roof tiles in a snowy area load the roof. Therefore, the structural engineer must calculate the required dimensions accurately.

Roof rafters - roof beams

The rafters run from the ridge to the eaves, ie the gutter. They carry the entire load of the roof, therefore, their strength must be calculated sufficiently large also in relation to their length. This is done by a structural engineer or the architect.

He must take into account which roofing should be carried by the rafters. Conventional roof tiles, for example, weigh around three kilograms apiece.

Rafters - the usual dimensions: usual

That does not sound like much, but even with a rather small roof, over 1,000 of these roof tiles are on the construction. Considering the potential snow load in winter, these three to four tons can gladly double again.

Dimensions for rafters in the overview

These sections are used depending on the statics as rafters, you get them in the timber trade in different lengths as needed.

  • 60 x 120 mm
  • 60 x 160 mm
  • 60 x 180 millimeters
  • 80 x 160 mm
  • 80 x 180 millimeters
  • 80 x 200 mm
  • 80 x 240 mm
  • 100 x 200 mm
  • 120 x 200 mm
  • 120 x 240 millimeters

Supporting or cantilevered

The calculation of the correct dimensions also depends on whether the rafters are intercepted on their length again, by an upright pillar or a crossbeam. Then rafters with a smaller cross-section are usually used.

Tips & Tricks

Even with a small structure, such as a garden shed or a carport, you should not try the calculation yourself. Always ask a specialist for the dimensions of rafters you should use.


Video Board: How to calculate the length of roof rafters (captioned)