Expert: Bruce E. Johnson - 2/24/2009

Question
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, you are better off running your rafters the 14' direction.  22' is a long span for nominal lumber of any size. I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com

---------- FOLLOW-UP ----------

QUESTION: Bruce,
Thanks for your quick response. Just one more question. Since I would then run the rafters the 14' direction could the  2x8 beams (which would sit right on top of the posts) go the 22' direction? Thanks again!

Dan

Answer
Hi again Dan, you are attempting to do something that just won't work.  22' span is pretty much out of the question for material of any size unless you are talking 6x18 beams.  You need to add a post in the middle and reduce the span to 11'. You may be able to add knee braces off each post to reduce the span somewhat but you are better off adding the addtional post.  I hope this information helps feel free to write again regarding this or other matters, sincerely, bruce e johnson..bejohnsonconsulting.com