Construction Purlin Flat Roof

Fasten the purlin with 16d common nails into each vertical rafter.

Construction purlin flat roof.

A common arrangement is a rafter and purlin system which combines purlins and rafters. Lay the first purlin at the ridge of the roof down to the chalk line beginning at either corner. The rafters are generally spaced every 16 inches on center. For example an 8 x 4 under purlin would support the center of a row of 6 x 2 rafters that in turn would support 3 x 2 roof purlins to which the roof cladding was fixed.

Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member. Here is the formula for calculation of a roof purlin. Under purlins were typically propped off internal walls. Roof live load roof dead load x spacing x span of purlin 2.

Insert two equally spaced nails into the rafter. 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. The roof support system is a ridgepole and either rafters which run perpendicular from the top of the walls to the ridge or purlins which run parallel to the ridge.