Construction Purlin Flat Roof

These structural supports run perpendicular across the rafter beams.

Construction purlin flat roof.

Or less x 1 1 cfu the flat use factor for applying the load to the wide face of a member. Purlins are 2 by 4 feet and are installed much like metal roofing. 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. Metal building roof purlins provide three structural functions.

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 higher the snow load the closer the purlin spacing required. Roof live load roof dead load x spacing x span of purlin 2.

The common 4 on center design is suitable for snow loads up to 60 for most applications. Metal roof purlins are installed horizontally under metal roofs. The purpose of purlins. Purlin plates are beams which support the mid span of rafters and are supported by posts.

Purlins are an important component in a pre engineered steel structural kit. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. Also known as sheeting rails purlins create the roofing members of the secondary framing of a steel building. Purlin plates in wooden construction.