In the next fields of the calculator, decide whether you want to include the costs of installation in the calculations. Our tool can also figure out the approximate roof truss cost. Input the roof length, the on-center spacing (the distance between the middles of two neighboring roof trusses), and the roof truss calculator will return the number of roof trusses needed. You can input the roof pitch in any of the three formats (angle, percentage, ratio), and our tool will automatically tell you the other ones. You can input any of the two values to get the third one calculated. Here as well, our calculator works both ways. After doing that, you will see the rafter length in the bottom field. If you decided to include roof pitch in your calculations, to get the rafter length, you will need to input the run and the pitch of the roof. That is, you can also use it to calculate the rise or the run! If you already know the rafter length and want to figure out any of the other dimensions, simply input the two you know, and you will get the third one. Please note that the rafter length calculator works both ways. If you picked the rise, all you need to do is input its value, put in the roof's run, and the calculator will return the rafter length in the bottom-most field.

If you want to learn more about the way it's calculated, check out our roof pitch calculator. You can choose the rise of the roof (which is its height), or the roof pitch (which is the slope created by the rafter). Start by deciding what you want your calculations to be based on. In the field above the illustration, pick either 'rafter length' or 'truss count'. To start your calculations, you need to choose from the two options mentioned above. You can use it either as a rafter length calculator, and get the dimensions of your trusses estimated or as a roof truss count calculator, which will also allow you to estimate the roof truss costs and even include the price of installation. Our experts are standing by to take your call now to answer questions about our metal building roof purlins.Our tool has two applications. 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 spacing for metal roofing