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.

Construction purlin flat roof.

Purlin plates are beams which support the mid span of rafters and are supported by posts. 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. By supporting the rafters they allow longer spans than the rafters alone.

These structural supports run perpendicular across the rafter beams. Purlins are an important component in a pre engineered steel structural kit. Metal roof purlins are installed horizontally under metal roofs. 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. Metal building roof purlins provide three structural functions. A purlin plate in wood construction is also called an arcade plate in european english under purlin and principal purlin. The purpose of purlins.

Purlin plates in wooden construction. The common 4 on center design is suitable for snow loads up to 60 for most applications. 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.