I would like to place a hot tub on my balcony, and need help to double check if my floor joist can handle the load. I have have 2 x 12 floor joist @ 16" o.c. with 3/4" plywood decking and 1/2" drywall on the underside. My floor joist sits on the full 8" of the block wall below and sits on top of the full 8" of the 16" concrete lintel on the outside which leaves a clear span of 6' - 4" for the 2 x 12 floor joist @ 16" o.c.

According to the manufacture specification, the hot tub when filled with water weights 125 lbs per s/f dead load, this does not include the live load. The hot tub Model is called Softub Legend 220....This 125 lbs per s/f does not include up to people 4 people. I will have a total of 2 adults and 1 child. Can someone help me verify if the floor joist can handle the load of the hot tub.

  • I presume the 125 lbs per sq/ft includes water... Are you including factors for the live loads of people who may want to use the hot tub? Don't forget that these may be over used (more people than the recommended capacity) or people in the tub and more people on the deck outside the tub, especially if there are younger people around.
    – FreeMan
    Commented Jun 11, 2020 at 14:09
  • 3
    Given that this is a CRITICAL structural calculation, meaning people could DIE if you get it wrong, it's not really appropriate for you to use anonymous internet sources as a substitute for paying a structural engineer to do this for you. You must also deal with local building codes, seismic aspects (if any) in your area etc. etc. etc. We have no way to know any of that.
    – JRaef
    Commented Jun 11, 2020 at 17:00
  • "Assuming the worst case having 2 x 10 floor joist" Do you mean you do not know what size the joist's are? There is no place for assumptions here; you need to know. Where does the 125 lbs per sq/ft come from. You need to know the water weight by cubic foot, ( or by gallon at 8 lbs per gallon ) the weight of the tub and the people in it.
    – Alaska Man
    Commented Jun 11, 2020 at 17:03

1 Answer 1


Balcony = Supported by hidden joists under its floor. Deck = Supported by joists or/and piers.

Now if you have a balcony and given your question with lack of some information...

You are capital letters CRAZY for installing a hot tub on a balcony. For something that heavy you would have to be assured metal joists or deep span (that might not be enough). I would surely get an engineer OK (which no engineer would with this info) before doing so.

Even if you get past the fact that something that heavy could trigger a quick collapse on a balcony (decks are more apt to give you lots of clues if they are collapsing), collapsing isn't the only thing you have to worry about. If this thing is so heavy it bows the support joists you could be looking at 10k+ in damages. Super costly to repair something like this on a finished unit.

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