Flat Roof Purlin Spacing

2 are indicated below.

Flat roof purlin spacing. A metal roof must also allow for some overlap on each side of the panels which will reduce the effective width of the panel. Here is the formula for calculation of a roof purlin. 1 psf lb f ft 2 47 88 n m 2. Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member.

Dead load weight of structure and fixed loads 15 lbs ft 2. Roof pitch use recommended minimum roof pitches as specified by roof sheet supplier. 8 x section modulus of a 4 2 of 1 3125 x fb fiberstress in bending x 1 15 duration of load x 1 15 cr repetitive member factor as the purlins are spaced 24 o c. Roof live load roof dead load x spacing x span of purlin 2 divided by.

Standard gage are generally used for roofing. Further to be considered is the roof framing system as a whole be it truss or rafters wood or steel as the case may be is a factor how purlins are installed at calculated distances apart. Posts these span tables are designed for a minimum post size of 50 x 50 x 2 5mm up to a maximum height of 3 0m. Wider panels allow for greater spacing between rafters.

Live load is weight of furniture wind snow and more. It is understood that purlins are spaced where laps and splices of roof sheets that vary in sizes. The spacing of purlins on roofs and girts on wall is usually 4 to 6 ft. To determine how far apart to set rafters measure the width of the metal panel and then the width of the first hill and valley of the panel.

1 ft 0 3048 m. Doubling up in the valleys refer to the installation manual for the proper on center spacing and be sure that the purlin is attached to the roofing truss. In the valleys due to the angle typically produced at the valley and the use of transition flashing it is essential that the purlins are doubled in the valleys that is two purlins side by side on each side of the angle of the valley. Flat roof span tables allow for a maximum roof pitch of 5º.

Numbers 20 and 22 u s. Non accessible roof and intermediate 1 600 2 400 1 500 2 100 wall cladding type 3 end 1 100 1 600 1 000 1 400 maximum recommended purlin intermediate 0 900 1 500 0 800 1 200 spacing for standard roof end 0 600 1 000 0 550 0 800 see notes below. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.