Installing a Hot Tub: Can You Put a Hot Tub on Gravel?

hot tub gravel

Considering a DIY spa installation? Here’s what you need to know.

There’s a lot to think about when you are planning for your hot tub’s arrival. But it’s important to start from the ground up — literally. Choosing the right foundation for your hot tub will help you protect your investment and keep your mind at ease.

However, there are a lot of options for your hot tub foundation. You can put a hot tub on your deck or on an existing concrete patio. You can put it inside or create a vault so it looks built-in. But those installations can increase the cost of your hot tub. A hot tub base like pavers or gravel can be an affordable DIY option for new owners.

A member of the PoolSpaForum recently asked if it was OK to put gravel over pavers for a hot tub foundation.

Initially, he wanted to put the hot tub on flagstone pavers. The pavers had settled, though, and the foundation was no longer level. Not only could the uneven pavers compromise the structure of the hot tub, there could be issues with drainage.  

In the post, the member asked: “So what I’m attempting to do is build a wooden frame on top of the existing pavers and fill that now level frame with 3/4 crushed granite. Will this work putting this gravel over the existing pavers?  They would be hard to remove as they are almost grouted in or something. Also do you need to top with the pea gravel or can I just use the 3/4 gravel up to right below the top? Is it hard to level 3/4 crushed granite?”

spa on rock patio
If you want to put your hot tub on gravel, be sure to properly prepare the site.

Installing a Hot Tub on Gravel

Gravel is a popular alternative to a concrete pad for hot tub owners. It might appear to be lower in cost and easier to install, without any permits. The project could take a weekend with some help from friends. 

Putting a hot tub on gravel, though, does not mean pouring the stones onto your grass and walking away. The site has to be prepared properly so that it can support the weight of a hot tub. 

Putting a Hot Tub on Stone

  • Mark the area where you want to put the hot tub. Reference the model specifications for your hot tub on the manufacturer’s website. Be sure to add a bit on each side to make sure the space is big enough.
  • Dig down six inches inside the area that you marked. Why six inches? You want the pit to be deep enough for proper drainage but not so deep that the base becomes too soft. You want to make sure that the bottom is as level as you can. Use a tamper to compact the earth and make it as smooth as possible. Depending on the size of your hot tub, you can also rent an electric tamper to make the job easier. 
  • You will want to use a landscape cloth as a barrier between the dirt and the gravel. 
  • Begin to fill the pit with medium-grade gravel. This gravel should be about four inches deep.
  • Fill the remaining space with pea gravel, or another smaller gravel. Use a rake to smooth out the gravel.
spa on rock
Check with your manufacturer’s warranty to see whether it is OK to put your hot tub on gravel.

Reasons NOT to Put a Spa on Gravel

Most hot tub manufacturers recommend installing a hot tub on a reinforced concrete pad. Not only does it offer a level surface but it can support the weight of the hot tub filled with water. 

When it is properly installed, a gravel pad can support the hot tub. However, there are some downsides to using gravel for your hot tub foundation.

  • Gravel can wash away, depending on where you live and the slope of your yard.
  • You should also consider the type of soil that you have and how it settles. If you live in a colder climate, you also have to factor in the ground freezing.
  • A DIY gravel pad might seem like an easy project but might take up more time than you anticipate.
  • Some DIY tutorials for putting a hot tub on gravel also include constructing a wood frame, which might be unexpected. 
  • Putting your new spa on gravel could also void your warranty. 

Before you choose the base for your hot tub, it’s important to look at what will work for your space and budget while keeping your hot tub protected.

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