Freestanding deck to support a hot tub.

Old 10-17-17, 10:42 PM
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Freestanding deck to support a hot tub.

I am building a 12'x12' section of a deck that will be eventually be built into the rest of my deck (12' x 28', and 16' x 18' L Shaped) when funding and time allows. I plan on digging nine holes for concrete piers 5' OC. I will be using 12" x 48" tubes and concrete set 3" above grade. I will sink metal post bases into the concrete, using 6x6's for the posts. These will be around 10" in length due to the finished deck height of 28" above grade. I plan on doubling 2x10x12's for the beams running with the line of the house across each set of three posts connected with post top brackets, and want to install 2x8x12 joists on top of the beams spaced 12" OC. 5/4 deck boards to finish, running with the house.

The hot tub is a 7x7 tub but I'm not exactly sure how many gallons this tub holds. A similar tub is listed at 350 gallons, which comes out somewhere around 3000 pounds for the water and an 875lb dry weight. I'm estimating around 5000lbs filled with water and people.

Does this sound adequate to you? I always second guess myself with things like this.

I've attached a quick sketch of what my plan is. I have a detailed drawing at home in my workshop, this is just something I threw together quick. It says 16"OC for the joists but I'm planning for 12".
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Old 10-18-17, 05:55 AM
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At 5000 lbs, or 102 lbs per Sq foot, a hot tub far exceeds the weight/ span tables most carpenters have available to them. When that happens, you need a structural engineer to step in and do the math. Sometimes there will be someone qualified at your local lumber yard who will be willing to help you design... other times you have to bite the bullet and pay someone to do it. I doubt anyone here has the expertise to do that for you.

That being said, if you know you will have a hot tub at a certain location on your deck, I don't know why you wouldn't excavate a perimeter footing, form a wall, and pour a concrete pad for it to sit on. Your deck framing could then attach to that foundation (a ledger), surrounding the hot tub. The rest of your deck construction would be normal... it would no longer require the beefy construction.

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