Timber Roof Joists

Joists are traditionally made from timber.

Timber roof joists.

Timber to be covered these span tables do not apply to timber which is fully exposed to the elements. Here we have a wood framed gable roof. Harmony timber are manufacturers of timber frame roof truss kits and open metal web joists based in county wicklow ireland. Floor beam span tables of residential structural design we will now look at roof rafter and beam design.

The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. Timber joists joists are the parallel horizontal beams that run across an open space joining opposite walls in a building to support both the ceiling below and the floor above. Notches are not to exceed 0 125 of the depth of the joist and are to be located between 0 07 and 0 25 of the span from the support. These span tables apply only to flat roof and roof with a slope of up to 10 degrees.

Usually 400 450 or 600mm but any value can be used up to 610mm max usually 400 450 or 600mm but any value can be used up to 610mm max 1 2 timber strength class and joist size. This is the distance between joist centres. Let s consider a basic gable wood roof framing design.