Timber Roof Joists

Let s consider a basic gable wood roof framing design.

Timber roof joists.

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. Continuing on from part 3. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. 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.

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. These span tables apply only to flat roof and roof with a slope of up to 10 degrees. 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. Here we have a wood framed gable roof.

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