In building an elevated deck over 6x6x6 posts, a beam made of 3 pressure treated 2x8x16' (where the beams are attached to each other with FastenMaster ThruLoks) is too narrow (~5" versus 6" expected) for the galvanized-steel beam holder resting atop the post. I suppose this is due to nominal widths of the lumber, but I read this technique was acceptable if you could not get a beam and wanted to build it yourself with 2x8x16' pressure treated lumber. Where did I go wrong and what can I do to keep doing this right?

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2 Answers 2


Getting the right size bracket isn't a problem, if you go to Simpson Strong Tie web site, or other comparable brand, you'll find a part number to fit your beam and post sizes. Look at the PCZ6. Or on this catalog page, the CC4.62-5.50:


Just make sure that the built up beam you made is adequately sized for the load. A built up beam made from three 2x8's may be strong enough for your deck but it is not as strong as a 6x8 beam.

  • Your last statement seems to ignore the primary benefit of plywood. I'd bet that, on average, a compound beam would be stronger.
    – isherwood
    Commented Dec 24, 2018 at 2:24
  • @isherwood - I don't see mention of plywood, it seems like the OP's plans called for a 3"x8" beam and he substituted a beam made of 3 2x8's, less wood, no plywood. Commented Dec 24, 2018 at 2:32
  • I was speaking generically with respect to laminated lumber of all sorts, such as LVL beams.
    – isherwood
    Commented Dec 24, 2018 at 13:26

If the beam of three 2x8s is sufficient for the load, consider filling out the space in the post connectors with sliced scraps of the 2x8s you used for the beam.

EDIT You could center the beam and put slices on each side.

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