Construction Purlin Flat Roof

Purlins are 2 by 4 feet and are installed much like metal roofing.

Construction purlin flat roof.

The common 4 on center design is suitable for snow loads up to 60 for most applications. Too high a snow load means the purlins fail regardless of how close together you put them because a 2 4 or 2 6 flat can only span a certain distance between trusses as snow loads increase. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. Purlin plates are beams which support the mid span of rafters and are supported by posts.

Purlin plates in wooden construction. 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. These structural supports run perpendicular across the rafter beams. Metal building roof purlins provide three structural functions.

Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. The higher the snow load the closer the purlin spacing required. Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member. The purpose of purlins.

By supporting the rafters they allow longer spans than the rafters alone. Roof live load roof dead load x spacing x span of purlin 2. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.