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Span Tables for wood roof purlins

Span Tables for wood roof purlins

I am working on a design using parallel chord roof trusses @ 7'-6" centers.  The trusses are alrady calculated and confirmed by the manufacturer.  I am looking for a table which will give allowable uniform load on a 4 X 4 (nominal)
spruce purlin.  Design spacing is 26" centers.  Purlins are supporting a corrugated metal roof panel and 45 psf snow load.  Total load on each purlin is 815 pounds assuming 5 psf dead load.  Connectors for wind uplift etc. are already considered - just trying to confirm spacing is OK.



RE: Span Tables for wood roof purlins

Thanks for the link and the tips.  They were very helpful.


RE: Span Tables for wood roof purlins

The beams you selected will not work.  Both delfection and bending are way above allowable.  Need to look at bearing loading to.  You need to consider having someone (professional) help you design the system.

RE: Span Tables for wood roof purlins

I agree, thanks again.  Before turning it over to an engineer I was attempting to get the structure in the ball park, for budgeting.  I pulled the allowable uniform load from a National Forest Products Association Table @ 801#, but as you say there is more to look at.  I do intend to run each purlin over two spans.  I would prefer to keep the 4 X 4 profile and change the spacing to permit this (unless it becomes ridiculous).


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