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Clear Span Roof Truss Calculator

Started by Sedgehammer, February 05, 2019, 12:00:58 PM

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Sedgehammer

question though. you mentioned 4-6" on the edges and 12" in the field. On a typical house trusses, they are screwed down only where there are the trusses of course, so why all the extra?
Necessity is the engine of drive

Don P

On the trusses, purlins or rafters, 4-6" along the sides of the sheet to keep the edges down and transfer racking loads. In the rest of the sheet 8-12" along every rafter to keep the sheet flat when the racking tries to pop the sheet out of plane. For the other 99% of the time it keeps the sheets flat on the roof from warping. The roofs with 8 or 10 nails in them are the ones you see heading cross country in high wind, a roof gets down pressure but also lift and racking as wind passes over it.

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