We are planning a small narrow "pergola". Actually it is a weird combination structure. My husband wants a pull-up bar, I want it to be a landscape feature that looks nice, and it will be alongside/part of a new fenced veggie garden. So we're talking 3 paired 12' 4x4s (8-9' aboveground) connected by pipes (the pull-up bars), but topped with typical shaped pergola-style side and cross beams for looks and climbing edibles. One side will serve as part of the garden fence as well. As a landscape feature it will feel like an "allee" or tunnel, at 4' wide and 16' long. Since it's detached and small, I have gathered I don't need a permit (SD County). But I looked at their pergola guidelines and they call for 6x6 min posts and 12" concrete footers. We were hoping to do 4x4 posts in 8" concrete. Too wimpy? Or is 6x6 and 12" overkill? (possibly for fire issues, not huge for us here)
After reading here and elsewhere my plan was:
-- Treat ends of (non PT) posts with Coppercoat just past level of concrete footing.
-- [Include bolts in posts to grab concrete?]
-- Dig [8" or 12"?] holes, pour 6" gravel, push posts in 2"
-- Using tube, pour concrete, shaping top for water runoff (level, brace of course)
-- When dry, caulk edge of wood/concrete interface
-- [Add post collar?]
-- Add top beams, fence stringers, etc.
-- paint everything, covering coppercoat too.
I should add being San Diego we get no frost heave -- no frost at all for us! -- and little rain. But clayey soil.
Thanks for your kindness if you can address any of my questions:
-- Are 4x4 posts enough? or 6x6?
-- Are 8" footings enough? or 12"?
-- Are bolts in the posts in the concrete really helpful?
-- If we're using concrete, can we cheat on the 1/3 rule and have 3' in-ground and 9' above-ground?
-- Why doesn't a post-collar hold water against the wood? Because of the glue? Are they really worth it, or overkill?
Thank you folks!