rafter and purlin spacing for metal roof

Determine the load requirements: Assess the expected loads on the roof, including the dead load (weight of the roof covering material) and the live load (snow, wind, or other imposed loads).

The choice of material depends on factors such as the design requirements, local building codes, and personal preference. Common materials include steel, wood, or aluminum.

Identify the material: Determine the type of material you plan to use for the purlins.

Determine the span: Measure the distance between the roof beams or trusses where the purlins will be installed.

Here are the general steps involved in calculating purlin size: Purlins are horizontal structural members that provide support to the roof covering and transfer the load to the main roof beams or trusses. To calculate the size of purlins, you need to consider several factors such as the span of the roof, the type of material you’re using, and the expected loads the purlins will bear. Our experts are standing by to take your call now to answer questions about our metal building roof purlins.Purlin Size Calculator Purlin Size CalculatorĬalculate How do you calculate purlin size?

Pre-welded clips simplify construction and speed up the purlin framing process.Ĭall RHINO today at 940.383.9566 to learn more about the cost-effective RHINO Difference of low-rise construction. Moreover, RHINO rafters have factory-welded clips already installed for attaching purlins. The amount of lapping increases as the load increases. Consequently, all RHINO purlins overlap by design. The greater the amount of overlap between connecting purlins, the stronger the connection will be. However, at RHINO, we design our purlin systems for maximum strength. Some steel building companies provide purlin connections that butt flush against each other on the rafter. Taller purlins also allow room for increased insulation.įor coastal climates where high-humidity or salt corrosion poses problems, RHINO offers optional galvanized purlins, if desired. If your design or local building codes demand extreme spans or snow loads, taller purlins may be required. Traditionally, RHINO steel buildings use 8” to 10” primed red-iron C-purlins and Z-purlins. The heavier the expected load is, the shorter the distance between the purlins. However, engineering determines the optimal roof purlin spacing. On a standard load, most designs call for purlin placement at five-foot intervals. The eave purlin marks the first purlin at the wall connection. When looking at the ends of the rails, the purlins shapes look like the letter “C” or the letter “Z.”

These purlin styles get their names from their shapes.

In general, metal roof purlins come in two varieties: C-purlins and Z-purlins. Consequently, a metal building system saves money on both building material and labor. Steel building purlins eliminate the need for oriented strand board (OSB) or plywood decking. It is also time-consuming to install, driving up labor costs. Wood framing employs decking to tie roof trusses together and support the roof. Thirdly, purlins add additional support between the spans of the individual framing bays.Īs an added bonus, metal roof purlins increase the structure’s resistance to strong winds.Secondly, purlins tie the rafters together, stabilizing and strengthening the structure’s rigid framing.Metal building roof purlins provide three structural functions: These structural supports run perpendicular across the rafter beams.Īlso known as “sheeting rails,” purlins create the roofing members of the secondary framing of a steel building. Purlins are an important component in a pre-engineered steel structural kit. What are purlins on a roof? Let’s get down to the basics of metal building roof purlins. What Purpose do Purlins Serve on a Steel Building?

Rafter and purlin spacing for metal roof