Timber Roof Joists

Let s consider a basic gable wood roof framing design.

Timber roof joists.

Continuing on from part 3. 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. Here we have a wood framed gable roof. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial.

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. Joists are traditionally made from timber. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Timber to be covered these span tables do not apply to timber which is fully exposed to the elements.

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. Harmony timber are manufacturers of timber frame roof truss kits and open metal web joists based in county wicklow ireland. They are nominally 2 inches thick actual width usually 1 1 2 inches and come in a variety of widths from 8 to 12 inches.