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I am building a deck. I have most of things sized out properly I think. I just want to confirm that 12" piers are enough for what I am doing. This is a freestanding deck next to a pool.

Did I draw my areas for loading pretty close? The largest one I have is about 21 sq ft, which means the 12" piers should be plenty.

Beams are doubled 2x8, joists are 2x8. All posts will be > 1' from edge of pool, but I had to get pretty close due to the wonkiness in the lower left corner. (Even still, that last joist has a cantilever of about 1'9", so I could push it back a hair more if needed

Piers

Joists

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    Although there are probably experts on this forum that could provide an answer for you, this is a safety question and you should not rely on on-line answers. Who is responsible if you follow our advice and an accident results? You will need to get a local building permit anyway so you should consult local experts.
    – Barry
    Apr 20 at 22:49
  • Are you asking about 12" depth for piers? Unless your in the deep south a 12" depth for the piers doesn't seem like enough because of possible frost. You need to be sure they're below the frostline. In Colorado, for example, it's 36".
    – HoneyDo
    Apr 21 at 16:23
  • @HoneyDo very valid point, however I assumed (and we all know what happens) that OP was asking about a 12" diameter pier of appropriate depth. Maybe he'll come back to clarify...
    – FreeMan
    Apr 21 at 18:26
  • Yes, I was looking at 12" diameter pads, at about 42" depth
    – Akshue
    Apr 23 at 15:43
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I'm not a expert but the answer likely depends on exactly where you live. When I built my deck in Maryland the footings needed to 30" deep and 18" in diameter (for the bottom 8").

See local ordinances for Howard County Maryland.

If you are lucky your jurisdiction may publish their requirements. If they don't publish them you could give your local permit office a call.

Jonathan

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  • As an aside if your soil is anything like mine (mixed clay and rocks) you might want to consider increasing you beam size / checking maximum spans so you can reduce the number of footings and save yourself some digging.
    – jonathan
    Apr 21 at 0:06
  • I don't see too many posts that could be removed. Maybe convert 4 posts to 3 on the long 15' run or convert 3 to 2 on the right hand 9' run? Everything else is 2 posts, 1 beam...
    – FreeMan
    Apr 21 at 14:01
  • Agreed. Though you could probably also merge the two separate beams with four post on the front right to one beam. At least in my jurisdiction you are allowed a 2' overhang. If you converted the 4->3, 3->2 and the 2 separate beams to one with 2 posts then you would save 4 posts (and the footing underneath). It all depends on how bad the digging is where he lives.
    – jonathan
    Apr 21 at 23:11
  • Fair enough, point.
    – FreeMan
    Apr 22 at 11:47
  • thanks for the insight, guys... As far as combining the 2 beams to 1, I don't think it's possible - I'm trying to keep any part of my holes (14" holes for 12" footings) at least 12" away from the pool edge. Assuming I "nearly" center my post in the holes, my cantilevar on the joist ended up being a few inches more than 2' at the worst case area. (I think just the troubles with working around a pool)
    – Akshue
    Apr 22 at 21:19

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