Custom deck supporting a hot tub

by CPAnnie

We are building a 24x24 deck out of Azek (vinyl) deck planks and standard spacing of joists is 16" o/c. The hot tub will range from 4000-4900# filled and is going on one corner of the deck.

I know we need to make joists smaller on center for this load bearing application and believe there need to be added posts for support as well, however, I don't know what those numbers are.

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Jul 13, 2011
Use the footing calculator to get started
by: Editor-Rich Bergman

Yes by spacing the joists together you address the inherent strength limits of the joist material itself for that area of the deck supporting the tub.

But in the end all that extra weight is transferred down to the ground and dissipated over the area of each footing that the tub transfers load to. So you have to know the bearing capacity of the soil. You have to check locally what type of soil you have.

Once you know that you have to divide up your deck into tributary areas to determine how much weight is being imposed on each tributary area and thereby to each footing to the ground. This weight carried by the area of the footing must be lower than the maximum soil bearing capacity.

A great tool to use to play with all these variations is the Deck Footings calculator I built and put on the site this year. Check it out.

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