Deck to support spa
 

Building a new deck out of PT and want to incorporate a sunken spa. Figuring I'll need at least 100 psf, can someone please give me an idea of how to build the supporting platform for the spa (6x6). The bottom of the spa will be no more than 3 ft off ground. Thanks.

handi, I arrive at a figure of about 225 psf.
4500 lbs water, 300 lbs spa, 4 people @ 150lbs X min. safety factor of 3 = 16,180 lbs total weight and we go back to the post/slab/block construction that you don't like to hear about. In this instance you could cap with 2" PT lumber as heat isn't a factor.

I wouldn't recommend anything less than a slab. The amount of wood you would have to use to support the spa would likely cost you more than the slab. The slab won't collapse, the deck probably will.

I agree with this because I saw it first hand. The deck was only 5ft off the ground so they dropped a spa in with extra wooden supports. During the night (after 2 years) the whole deck came down with the spa. What a nightmare. Spa was ruined, deck was ruined, it pulled a beam out of the stucco which tore from the back of the house. Probably cost the homeowner $20k to fix that mess. Always go with the safe route - if that guy was in the spa, he wouldn't be here today.