Flat roofs the recent and more onerous requirements of approved document l of the building regulations relating to energy conservation have shifted the emphasis for thermal efficiency from the building structure to the building envelope.
Purlins of flat roofs.
How to install metal roof purlins.
Run a tape measure from end to end along the rafters of the roof to determine how many purlins will be needed for installation.
Purlins placed flat will not span eight feet so eliminates this option.
Purlins are non pressure treated 1 x 4 x 12 lumber that is installed on to the roof in a specific layout pattern and screw pattern.
Purlins 24 spacing mike the pole barn guru writes.
Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member.
Lay the first purlin at the ridge.
Roof live load roof dead load x spacing x span of purlin 2 divided by.
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.
In timber construction purlins are nailed to the rafter or supporting trusses while in steel roof construction they are welded or bolted to the rafters or trusses by the means of cleats.
Snap a chalk line horizontally across the roof two feet down from the top.
Trusses most likely on 8 s.
Image copyright belongs to albion sections limited uk roof purlin are members used to directly support roof sheeting materials and could be made of timber or steel.