In general, 2x4s can be up to six feet long, but there are a few things to consider. How far can a 2×4 Rafter span without support?.Can I use pressure-treated wood for rafters?.What type of wood is used for ceiling joists?.What is the best wood to use for rafters?.Can I put a metal roof on without sheathing?.Do you need a vapor barrier under a metal roof?.How far can a 2X4 span for a metal roof?.How far can a beam span without support?.Higher quality applica- tion for raw materials like poplar wood can be part of a cascading strategy. In this case, more use is made of the resource potential of poplar, as it is applied as a structural component with a long life span. … The vapor barrier built into such insulation helps to minimize the amount of condensation that drips down from the roof, and the insulation itself can help to keep the interior of the building at a comfortable temperature.Īs an example of a high quality application a purlin made out of poplar is chosen. Rafters may be spaced up to twelve feet, dependent on purlin size, when purlins are turned edgewise.Ĭan you put metal roofing directly on rafters? Metal roofing can be installed directly on open rafters. A ten-inch purlin can span 30 feet.Ģ×4 purlins may also be nailed on top of the rafters with one 60-d nail or attached with metal clips at each rafter. Spacing is typically 24″ on center in low snow loads and is reduced based upon truss span and snow load.Ī four-inch purlin can span 12 feet. The purlin are ultimately used to fasten the roof steel providing a diaphragm effect, along with the siding, when properly engineered and installed.

Rafter spacing for metal roof