What is the Best Base for a Hot Tub?

I's say contained gravel would be fine.

Yes, stake it, on the inside so they don't show.

Happy soaking.

an engineer is never going to suggest cheap or flimsy! get out the I- beams and piledriver

As any true hot tubber will tell you, it's not what you put under the hot tub, it's what you put in it....

I would use crushed stone rather than gravel, gravel tends to migrate, the pebbles slide over each other too easily, something akin to seating the tub on a bed of marbles.

Gravel (comics) - Wikipedia, the free encyclopedia

OOPS wrong button.

I wanted permanence and the 2-person Jacuzzi Tub manufacturer suggested a fine concrete mix (this is an indoor tub/shower). 2x8 supports on 8 inch centers with 1-1/4" plywood on top, then builder's paper and then the cement poured on top of that and spread out so it was just a bit taller than the bottom of the tub.

Set the tub on top if that and jiggled it until the tub edge supports grounded on their structural supports.

15 years later the tub is still solid with no bottom flex anywhere.

Saving money on construction materials is, in my opinion, a bad place to save. Labor is the big ticket in most cases in the U.S. A building will last at least 50 to 100 years and it would be nice to have the infrastructure last as long as possible.

I have foam supports under the plastic tub in my motorhome. The bottom flexes everywhere. Bad idea in my opinion to use foam.

Possible problem with gravel sand or and form of crushed stone subbase unless compacted properly it could settle and cause the tub to become unlevel causing problems for the pump. That's why usually wood decks and concrete pads are the better choice. You might also want to check with your local government they usually will tell you what the local regulations and permits are.

TCMTECH had a great suggestion with the 2" foam under the tub. We have used this as standard procedure for installs for quite a while. One really should construct a rigid level platform for the tub to rest upon. Concrete is probably the best but a well constructed wood deck will do fine. Any differential settlement under the tub could wreak havoc with the plumbing connections etc. For my tub I precast a concrete deck and placed it on two concrete footing strips so it could be re-leveled in the future should the sheltering trees cause problems with their root structures. Probably overkill, but if building a wood platform you can purchase support brackets with leveling screws that would afford the same flexibility. Whatever the case, the most important thing is to get it installed, filled and enjoy.

What is the connection between Cement, Gravel, Concrete and Mechanical Engineering? ROFL

Pls move this crap to Civil Engineering section!

Better yet, move to another forum.

I'm going to guess you're artsmith in the AP1 troll suit.

Thanks for the input! I never thought about putting foam down. I am assuming a lack of consensus means any of the above will be OK. I will go with CR6 which costs $20/ton and the delivery is cheap being only a few miles from the closest source.

I put crushed stone and gravel in the same category. I have used CR6, a road foundation, for a shed base over 10 years ago. The deepest parts are over 18". I live on a hill and have little level ground. The shed is 25' long. The high edge of the ground where the shed now lies was removed and the low points were filled. I double-checked the settling last evening. The bottom of the shed is a framework of 2x4s set edge-wise. Where I could see the 2x4s settled into the crushed rock, it was surprisingly uniform, about a half inch whether the 18" or 6" deep. The foundation had been sitting for about a month before the shed was laid. Crushed rock tends to solidify over time and rain speeds up the process. The foundation probably have at least a dozen thunderstorms before the was delivered. Our area usually has a short violent thunderstorm every evening in June and July. The shed manufacturers suggested finishing the foundation before starting the work order. That gives the foundation about a month to harden.

This is a tiny project about 1 ton of CR6 vs 7. I will rent a vibrating compactor to speed up the settling process. The best part about a gravel/CR base is if we or the next owners want a bigger hot tub they will not need jack hammers to remove the old base. We are over sizing the base by a few inches for this and other reasons. Anyone can add and possibly remove some of the base to accommodate a new spa height. This is replacing an old hot tub sunk into a deck but supported from a base. The old one had a wooden base custom made to support the hot tub supports. This new design allows us to use a freestanding hot tub.

By the way Mr Anonymous, I searched for something like concrete in both Civil and Mechanical Engineering and there were many more hits in Mechanical so I placed the query here.

after you pour your stone (assuming you're passing on concrete) make sure to use one of these.

Jumping jack is another tool that will give you compaction.

you should put it in my yard for about a year to test run the system. you are welcome to come by every couple of months and try a different base until you find the best fit.