Expert: Dave Johnson - 6/22/2008

Question
Why other than cost on a stick built roof do framers use 2ft. centers on roof rafters instead of 16in. centers the roofs I have seen are all on a 8/12 pitch or greater does this relieve outward weight to the exterior walls are is it just cost effective? Is there any reason why you should not use 2ft. centers on roofs of this pitch?

Answer
hi jason,
usually, 24" centers are used with pre manufactured trusses, and 16" centers are for common on-site rafters.
the sheathing has to be thicker on 24" than 16".
there is little difference on the bearing weight.
there is no reason not to use 24" on this pitch, even with on-site rafters, as long as they are big enough.

Best of luck,
Dave