Construction Purlin Flat Roof

Roof live load roof dead load x spacing x span of purlin 2.

Construction purlin flat roof.

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. Insert two equally spaced nails into the rafter. Fasten the purlin with 16d common nails into each vertical rafter. Under purlins were typically propped off internal walls.

Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member. The rafters are generally spaced every 16 inches on center. Lay the first purlin at the ridge of the roof down to the chalk line beginning at either corner. A common arrangement is a rafter and purlin system which combines purlins and rafters.

Here is the formula for calculation of a roof purlin. Snap a chalk line horizontally across the roof two feet down from the top. In lightweight timber roof construction under purlins were used to support rafters over longer spans than the rafters alone could span.