I am installing a 12' x 12' pergola on top of my deck, it's a PVC kit but uses wood inside the PVC. It uses 4x4 posts. I am re-doing the decking so I can make framing modifications.

I was going to mount the 4x4 posts like I would for a railing post per the blocking guidelines in the image below, however since the pergola will have significantly more vertical weight than a simple railing post, I was wondering if anyone had any better suggestions?

I was thinking maybe mounting the pergola posts using the "Bolt Down Bracket Kit" option I can buy for the pergola, and for the framing underneath, maybe a 6x6 post laid sideways, mounted with throughbolts to adjacent blocking mounted with lag bolts. In my example below, the red lines indicate lag bolds, green lines through bolts, and the blue square would be the "Bolt Down Bracket" mounted with 6" lag bolts.

Here is a link to the Pergola assembly instructions

Blocking idea

Post railing guide

  • Lag screws. Bolts have machine threads. Anyway, your solution seems viable, but your question is fairly vague. That's not ideal for this site.
    – isherwood
    Commented May 3, 2021 at 15:55
  • It's hard to identify what your drawing is. Maybe label some of the lines. Is this supposed to be a drawing of your intended attachment method?
    – FreeMan
    Commented May 3, 2021 at 16:24


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