The Purlins for a Roof calculator computes the total number and length of purlins (roof support boards) based on the ridge length of the roof, the roof pitch and the span of the roof.
INSTRUCTIONS: Choose units and enter the following:
Purlins for a Roof (RP): The calculator returns the number and length of purlin rows for the roof. To calculate the number of boards needed for purlins, divide the length of the purlin rows by the length of boards you are using (e.g. two boards of length eight feet for each 16 foot long purlin row).
The Purlins for a Roof calculator is meant to help with material estimates for a metal roof. Purlins are typically 1"x4"x12' boards, sometimes called furring strips, that are used under metal roofs. They are typically untreated wood since moisture should be blocked by the roofing material. In all cases, confirm your estimates with a professional estimate and adhering to local building codes.
The calculator uses the ridge length for the length of the purlins. The spacing is used with the total rise and run to compute the number of purlins.