Can You Put a Hot Tub on a Gravel Base?


I’ve moved home quite a few times over the years, requiring me to have to lay a new base for my hot tub each time. So can gravel be used, and does it make a good base for spas?

Gravel is one of the best materials to use as a base for your hot tub. The gravel must be laid with a depth thick enough to support the weight of the spa. Gravel has many benefits such as being easy to install, providing excellent drainage, and is self-leveling. Pea gravel is the ideal size for using under your hot tub.

In this article, I show you:

  • Why gravel makes an ideal hot tub base
  • Which type of gravels are best to use
  • My step-by-step guide to building a gravel base

The 8 Benefits of Using Gravel

Gravel is inexpensive, simple, and low-maintenance. It is everything you want in a base for your hot tub. Gravel comes in an enormous range of styles and sizes and has many advantages over concrete, decking, patios, and synthetic pads.

Here are seven reasons why gravel is the best base for your hot tub:

1. Installation

With the least amount of effort, you can have a gravel pad ready and level for your hot tub to sit on. There is no waiting for gravel to dry as with concrete and, unlike other base materials, you do not need specific skills or specialist tools to lay gravel.

2. Drainage

There is a good chance that your hot tub will sit outside with a cover. But even if you build some sort of housing over your tub, there will be a lot of splashes as people step out.

Gravel provides excellent drainage for rainwater and any overflow should you accidentally fill your spa with too much water.

3. Aesthetic

Gravel helps to keep the area around your hot tub looking organized. Gravel comes in a range of colors and sizes, making it easier to match your home, yard, and tub’s color.

4. Clean

Gravel is the perfect material for separating mud from your tub. It won’t show footprints and is easy to clean. Gravel may need the occasional raking, but you can spray it down with a hose, and it will look like new.

5. Robust

Concrete is prone to cracking, as is wooden decking, and both are difficult to repair. Synthetic pads may wear over time due to splashes and overflow, as well as movement from the spa.

6. Drifting

Large slabs of concrete can begin to move on mud, which can cause the entire platform to tilt or slide downhill.

The growth of grass or other vegetation beneath a hot tub can also cause it to move around or lean. Gravel will self-level, filling in voids in the ground as it shifts.

7. Price

For cost-effectiveness, the price of gravel is hard to beat. The delivery of industrial bags of gravel is a quick and easy arrangement.

The truck should be able to lift the bag to the spot you need it on, meaning minimal work for you to spread and level it out.

8. Mold

Gravel will not rot or go moldy like wooden decking, so you do not need to treat It with special chemicals or paints.

Moisture build-up beneath the hot tub should also be minimal, and gravel will prevent direct contact with standing pools of water.

Which Gravel Is Best for a Hot Tub Base?

The recommendation for hot tub gravel is that its size is around one inch (25mm). Depending on the gravel you use, you may want stones with a smaller dimension.

Too large, and it is going to be uncomfortable to walk on. The drainage will be poor if the stones are too small. Classic gravel choices:

  • Bluestone gravel: More common uses include as an aggregate for cement and landscaping. The larger dimensions are better for drainage, but this type of gravel has sharp edges that make it uncomfortable to walk on.
  • River wash: A more expensive choice than bluestone or pea gravel, but the results are often far better. The colors go a long way to complimenting a hot tub. These stones weather well and offer excellent drainage.
  • Surge gray stone: Surge gray stone is like bluestone, though the dimensions tend to be in inches rather than fractions of an inch. Because of the larger size, the drainage is excellent, and it can be a workable solution for muddy ground.
  • Pea gravel: Diameters range from 1/8 to 3/8 of an inch (3 – 10mm) and look like large particles of sand. The edges are round, which is good for walking on, and you can find it in orange or gray.

You may find that smaller diameter gravel sticks to your feet, and larger chunks appear industrial. Pea gravel is a happy medium and one of the most popular choices. It is inexpensive, drains well, and looks great.

How Thick Should Hot Tub Gravel Be?

There is little point in making your gravel patch too thick unless you are trying to set your hot tub on mud. A depth of around a half-foot (15cm) of gravel is enough in most situations. This allows for settling and plenty of airflow for moisture release.

You can get away with a couple of inches of small pea or river wash gravel if you lay it over concrete. A landscape cloth may also help to reduce the amount of gravel you need to use.

How Do You Build a Gravel Base for a Hot Tub?

As with every building project, laying gravel goes much smoother if you have a plan. You want to finish with a level, smooth, and sturdy base that you can be sure is stable enough for a hot tub containing a few hundred gallons of water and people to sit on.

Step-by-step instructions for laying a gravel base for your hot tub:

  1. Ground – Find the driest and most level areas of your land where you could put the hot tub.
  2. Safety – Cross-off any locations that are near or over hazards, such as under power lines, over drain covers, near large panes of glass, or near trees with wide roots.
  3. Power – Your hot tub will need electricity, so try to locate it near your home. Most hot tubs need access to over 40 amps, so longer power cables for this level of power can get expensive.
  4. Water – You will want your garden hose to reach the tub in order to fill and top up the water on a regular basis.
  5. Landscaping cloth and frame – A landscaping cloth will prevent weeds from growing under the hot tub, which is a small, optional step that can save you grief later. You may also want to build a wooden frame around the area to keep the gravel in.
  6. Digging – It is worth spending time digging up a few inches of topsoil and grass to expose any roots or holes. You can also do some leveling so that the gravel layer is more consistent.
  7. Leveling – You can level the area out with gravel, which will give you a flat drainage platform to set your hot tub on. Four to six inches of gravel should be plenty for standard-size hot tubs.

I encourage you to read my guide on avoiding hazards when choosing where to locate your hot tub. There is a lot to consider besides practicality, with many dangers lurking in places you wouldn’t think to consider.

What is the Best Hot Tub Base?

Most hot tubs weigh less than 300 pounds (136kg) when empty, making them surprisingly light. But add the water and two or three people, and you are approaching 3,000 pounds (1360kg).

A six-person spa can be double this, which means you need to set it up on a strong and immovable surface to avoid disaster.

It’s a tough balance between having a strong enough base to cope with all that weight and something that fits the mood you are trying to achieve.

Gravel is a hot favorite because it is cheap and simple, but concrete is also a strong and popular base material. Here is a list of the most popular hot tub bases:

  • Concrete – A concrete pad may also need a reinforcing metal grid to help prevent cracking and separation. The best thing about concrete is that if you do it right, there is no limit to the weight it can support.
  • Gravel – Laying gravel is quick, and you do not need to be a professional to shovel gravel over a pad. Gravel is inexpensive and great for drainage.
  • Decking – Wooden decking looks the part, and you can find inexpensive boards that are strong enough for the job. You may need to add extra strengthening to support and level the deck. Decking may also take longer to install than the other methods.
  • Pavers – A simple and cheap method of laying a base, but these can sink. You want to make sure that they offer even support to prevent bending and damaging your hot tub.
  • Hot Tub Pads – If you already have a solid flat surface, you may want to consider hot tub pads. These are snap-together plastic pads that form a foundation and a barrier for your hot tub over grass, sand, or gravel.

What Is the Cheapest Base for a Hot Tub?

Gravel is by far the cheapest base material for a hot tub, as well as for ongoing costs. Leveling gravel is simple, and it offers the best effect for the least effort.

But beware that cheap is not always good, as false economies can end up costing you a hot tub. The first thing you need to do is to look at the ground you will be setting the hot tub upon. It may involve building a concrete foundation if the ground has a steep incline.

The roots from trees can cause problems with decking, so you will want a way to raise the hot tub up and onto a wooden platform. Cement can have the same issues, and roots will break through given time.

A hot tub set up on mud and sand may sink and slope, meaning you need to dig down further and replace more soil with gravel. Even if a root begins to push through a gravel base, it is easy to dig out so that you can deal with the problem.

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