Hi All,

Recently purchased 7'x7' Cal spa. My first question for the salesperson was whether my deck would support the weight. His response was that the spa equals out to 100 pounds per sq. ft, which is quite a bit less than a standing human. (My calculations actually come up to about 115#, and the spa documentation says 150 # per sq. ft.)

This seems to make sense, but I'm not totally convinced. I've asked several people and have heard a variety of responses. Most everyone thinks it will "be OK" but "maybe" extra support would be a good idea.

Thought I'd ask the experts before I put in any water.

Attached is a picture of the underside of my deck. The red square shows roughly where the (currently empty) spa is sitting.

Hoping someone can help me get an idea of what (if anything) needs to be done before I fill it up. Rebuilding the deck is really not an option.

Thanks!

Well, yes and no.

What you've heard is correct. However, do not expect the wood to live much longer in this condition.

You need to install 2-4 support columns underneath those joists. A hot tub, while 100-150 lbs per square foot sounds nice, itself will weigh in excess of 2-3000 pounds overall.

Imagine the effect of that weight after 2-5 years? (think... you're going to park a Volkswagen Passat on your deck like forever).

Yes your deck will sink. The joists will warp, and you'll be kicking yourself for not installing support previously.

Do it now. Get a couple of decent 4x4's with a cement block support to the ground and help your deck before it's forced to support something long term it was never designed to do in the beginning.

You should be able to do this for less than 40 bucks at any home supply store, like home depot or lowes, etc....

2 vertical 4x4's in the middle of your outline will be really great.

you could cut and screw 2x4's on to the 4x4 posts under where the beam is bolted thru. 4x4's had better be in or on concrete sonotubes. Deck should be lagged bolted to sillboard or foundation, if not already. Address those items and you will be fine.

Hi All,

I had a licensed/bonded contractor out to look. He installed 3 4x4's just under the 2x4 joists, with 2x6's right down through the center of where the spa is positioned. One of the 4x4's is right under the center of the tub, with one 4x4 each about 2-3 feet past the edge of the tub. All three are cemented in 24" of concrete.

I'm hoping this is adequate!

Matt