(1) Length of ridge beam, between supports; ( Lrb )
(2) Horizontal span (length) of rafters (or roof joists) on each side of the ridge beam, from ridge beam to support wall (or other beam) at far end of rafter. Spans are designated S1 and S2.
(3) Uniform dead load pressure in psf (wDL)
(4) Uniform live load pressure in psf (wLL)