Tables providing size selections for various beam spans and loading combinations for Southern Pine dimension lumber and Southern Pine glued laminated timber are available for the following applications:. For example, Douglas-fir is difficult to buy in some eastern markets. The table below shows an excerpt from a maximum span for built-up Douglas fir floor beams table for supporting not more than one floor. There are several beam span tables for all the species of wood.
Using span tables to size joists and rafters is a straight-forward process when you understand the structural principles that govern their use. I’ve excerpted the relevant sections from tables for hem-fir, Douglas fir-larch, and spruce-pine-fir (Figure 4).