Construction Purlin Flat Roof

The higher the snow load the closer the purlin spacing required.

Construction purlin flat roof.

They give added support to the roof and also provide a nailing surface for the end panels and drip edge. They are installed on top of the roof rafters with a felt underlayment or vapor barrier installed on top. These structural supports run perpendicular across the rafter beams. Purlin plates in wooden construction.

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. The common 4 on center design is suitable for snow loads up to 60 for most applications. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. 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. Purlins are an important component in a pre engineered steel structural kit. Purlin plates are beams which support the mid span of rafters and are supported by posts. By supporting the rafters they allow longer spans than the rafters alone.

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 term plate means a major horizontal supporting timber. Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. Metal building roof purlins provide three structural functions.