Expert: Dave Johnson - 4/12/2009

Question
Dave: I am building a pergola on a concrete slab that has been prepped for 6x6 posts (10'high)which are 17'o.c. apart. Will a pair of 2x8 beams for each length (from post to post)secured by carriage bolts be strong enough for hot and dry north Sacramento? I have metal footings inlaid with the concrete, there will be no load other than slats for purlins (it is a very simple design). Will these beams sag or otherwise twist? Thanks, Jonathan

Answer
Hi Jonathan,
Unfortunately, yes, I'm afraid thier own weight could make them sag
over time, but very little.
So, there are 2 choices, either put in an intermediate post or take a chance on little or no sagging.
As far as twisting, if you put your (2) 2x8's together with opposing grain, there would be no problem.
Best of luck,
And if you need more, mail me again...
Dave