Building Homes or Extensions/Pergola

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Question
Hi, I'm building a 14'x30' pergola for my patio.  
1. I plan on using 6x6 posts.  With a 1' overhang on each end, the outside posts would be 28' apart.  I know generally a 10' maximum distance between posts is recommended but I happen to have some 2x10 treated lumber left over from another project.  If I double these up overlapping (4x10), can I get away with 3 posts across at 14' spacing?
2. For the rafters, I have a 12' lateral span plus 1' overhang on each end totaling 14'.   Is it better to go with 2x6x16s and cut them down or double up overlapping 2x4s?
3. Finally, to set the posts, I understand the downsides of sinking posts directly into concrete but it seems the standard standoff post anchors are strong on compressibility but have very little lateral rigidity.  Is there a better solution than lots of diagonal bracing at the top of the posts?

Thanks for all your help,

Craig

Answer
Craig. I assume you are planning open wood work with no roofing.

Here is a site that will let you play with beam sag.  It is designed for shelving, but works quite well for beams:
http://www.woodbin.com/calcs/sagulator.htm

A 14' span on the 4" main beams should be fine.  Be aware that outdoor wood may well sag some as the years go by.

That long term sag will probably show with 2x4 spanning 12 and will also show on 2x6.

Wind bracing can be best handled with corner diagonals.  

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Dan Griffin

Expertise

I can answer almost all questions related to the total construction process. My expertise is in commercial construction, though I can field most any residential question. I have hands on experience in concrete, heavy equipment, masonry, all phases of carpentry, interior finishes, and I am fairly strong in mechanical and electrical.

Experience

I have over 20 years experience as a commercial carpenter and commercial construction superintendent. I have another 20 years experience in facility management for a major school district.

Organizations
My favorite hobby for he past 12 years has been singing bass in a The OkChorale men's barbershop chorus and the Mature Moments quartet.

Education/Credentials
I hold a Bachelor's degree in English and Math. I have completed many continuing education hours in the building trades. I hold a Master Carpenter card from the AGC, Associated General Contractors.

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