Roof Purlin Bracing

Purlin bracing is an angle that connects the bottom flange of adjoining purlins to prevent purlin roll.

Roof purlin bracing.

If you see braces which rest on ceiling joists look for a sag in the ceiling. Roof decking is often also used as a diaphragm to transfer wind or seismic loads to the lateral bracing system below. Roof purlin needs no introduction to anyone in the construction industry. Bracing purlin braces or any other roof braces ridge braces hip rafter bracing along with valley bracing must not be supported off the ceiling joists.

By supporting the rafters they allow longer spans than the rafters alone. To strengthen the roof system truss clustering cross bracing and wind bracing is recommended at both end of the buildings and every 20 for longer span buildings. The decking is sized to resist the bending caused by these loads. Flange braces can also be very useful as an erection aid to align the purlins and eave struts.

Wind and snow load. Structural design example four span metal building z purlin line supporting a standing seam roof. They provide lateral bracing to the compression flanges of the primary frame members to increase frame capacity. Purlins brace the roof panels while girts brace the wall panels.

Bracing must be installed off of walls or beams. Braces that rest on ceiling joists or which somehow pass the roof load to the ceiling below are defective installations. Purlin plates are beams which support the mid span of rafters and are supported by posts. The term plate means a major horizontal supporting timber.

During maintenance services and repairs and environmental loads e g. Purlin plates in wooden construction. Washington dc the american iron and steel institute aisi has published two new cold formed steel research reports. Purlins 24 oc are typical along with the bottom bracing shown.

Cold formed steel bracing design using combinations of discrete and sheathing bracing and rp20 5. In their design life purlins are subjected to dead load e g self weight of sheeting materials and accessories live load e g. Larger joist framing materials for instance 2x10 or 2x12 s can be doubled or tripled up with plywood in between and glued to create a flush. The bottoms of purlin braces should rest on top of a bearing wall.

Corrugated metal deck and siding is used for roofs and walls respectively to span between purlins for roof loads or between girts for wind loads. Like other frame members they are available with a galvanized finish and factory paint.