Construction Purlin Flat Roof

Purlin plates in wooden construction.

Construction purlin flat roof.

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. Purlins are an important component in a pre engineered steel structural kit. The higher the snow load the closer the purlin spacing required. They give added support to the roof and also provide a nailing surface for the end panels and drip edge.

Metal roof purlins are installed horizontally under metal roofs. These structural supports run perpendicular across the rafter beams. Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. Purlins are 2 by 4 feet and are installed much like metal roofing.

The common 4 on center design is suitable for snow loads up to 60 for most applications. Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member. Metal building roof purlins provide three structural functions. Purlin plates are beams which support the mid span of rafters and are supported by posts.

The purpose of purlins. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. The term plate means a major horizontal supporting timber. 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.