Can I put a portable hot tub on my second story deck? The deck has 8x8 posts and 2x10 joists. it is lag screwed into the sill plate between the basement and first floor of my walk out. The joists are 16 inches on center and from the ledger plate that is lagged to the house to the 8x8 support posts on the other side there is a span of 10 feet. The weight of the full hot tub with 2 people in it will be less the 2000 pounds.
Several assumptions are at play with this question. I going to assume that the hot tub is a 50" X 50" and you are using Douglas-fir for the 2X10X120 beams
Based on my research a douglas fir has a modulus of rupture ranging from 7 to 10 ksi
Using simple beam theory I calculated a maximum bending stress of approximately 1800 psi
that would be at the center of the beam
As you add more beams the load will reduce; this will depend on how big the platform area is
If you assume a 10' X 10' area then that is approx. 7 joists over the 10 ft span
so you load is rather low based on teh assumptions and my understanding of teh question
you shouldn't have any issues with the hot tub being placed on the deck that you have proposed
My calculations assumed a worst case scenario; meaning, I assumed one beam with a concentrated load at the center; then based on simple beam equations that calculate a moment of inertia based on a rectangular cross section; i calculate the bending stress (Stress = Mc/I)
I hope this helps; however, if you have additional info that may clarify any misunderstanding on my part please add if necessary.