The typical roof structure now consists of steel i beam rafters placed approximately 10 feet this varies depending on purlin size and other variables apart with either 4 6 8 or 10 lightweight steel purlins installed horizontally across the rafters.
Light weight roof structure.
In some instances either 6 8 or 10 c purlins doubled back to back can be used to as rafters as a substitute to structural steel beams.
In recent decades an expanding range of construction methods and building products particularly wooden truss roofing systems and wood i joists that together are often termed lightweight construction have been widely embraced by residential builders for their ability to deliver economy and functionality.
Lightweight sometimes a flat roof support structure requires a lightweight green roof.
Slate2 results in a 40 reduction in the overall weight of a similar traditional slate roof easily meeting the standard structural roof specification of less than six pounds per square foot.