The spacing between rafters in a given building is part of the engineering calculations that determine the required structure of the roof.
Is it okay to use 6x2 in roof struts.
The typical live load placed on a structure s roof varies by the building s use and location and weather is the primary concern.
If the bottom chord of a roof truss functions as a floor joist such as in an attic room it carries a live load that also varies by.
Answered 23rd feb 2011.
No need for purlins it would be a steel beam you would need to use but that is not necessery as it is only a lean to roof.
The ceiling joists create a truss to begin with i m suggesting adding another member to the truss.
Roofs are framed with rafters or trusses which are rafters joined by internal braces so they install as a single component.
This scheme is predicated on achieving serious load carrying connections well thought out and installed a 35 or l clips should to it at all joints.
Roof decking is often also used as a diaphragm to transfer wind or seismic loads to the lateral bracing system below.
Other relevant factors include the type of wood being used for the rafters the size of the rafters and the load that the rafters need to support.
The decking is sized to resist the bending caused by these loads.
The minimum plywood for roofing.
Tie to roof rafters at peak tie to ceiling joists roof rafters to ceiling joists at the eaves.
The purlins are supported by vertical or slightly angled bracing.
Load tables specifying safe loads for different spans are available from metal deck manufacturers.
The live loads a truss is required to bear are determined by local building codes.
Rafters run from the peak of the roof.