Expert: Dave Johnson - 2/23/2009

Question
I am building a 14'x20' pergola using trated pine. The four posts will be 6"x6". The beams will be 2"x8". Can I use 22' long rafters between these beams? Thank you for answering my question!

Dan

Answer
Hi Dan,
No. The carrying beams need to be much heavier.  The weight of the
joists alone will make the 2"x8" sag and over time they would collapse.

Any chance you could put the joists on the other (14') way? Then you could add another post mid-way on the long side, and use a beam of at least (2) 2"x8" splicing only over the post in the middle.

Best of luck, and if this isn't enough, please mail me again....
Dave