Hot Tub Base and Foundation Ideas

Are you planning to purchase and install a hot tub? If you are, you’re going to need a base for hot tub. So, if you’re looking for base or foundation ideas and which would be best for your project, we’re here to help!

A hot tub base needs to provide a strong, solid, stable, smooth, and level surface. It needs to support the weight and accommodate plumbing, electrical connections, and drainage. It also needs to meet building codes, HOA covenants, and warranties. A concrete or gravel pad or pavers typically meet all requirements.

In this guide, we’ll identify and explain the popular base types for hot tubs, including their pros and cons. We’ll discuss whether you need a base, what to put under an inflatable hot tub, if one can go directly onto the grass, and how to level the ground for a spa. Plus, we’ll explain what makes the best hot tub base. Our goal is to provide you with the information to make the best selection for your hot tub project.

Hot Tub Base Ideas

Popular Bases for Hot Tubs

There are many things to consider when looking at bases for hot tubs. You need to consider location, access, building materials, and if it will be a Pro or DIY installation. The weight and size of the hot tub are important too. Hot tubs can easily weigh 5,000 pounds or more when filled with water and people, so a proper base is needed to support all that weight.

Electrical and water hookups may also dictate the location, as may access. Hot tubs should be as level as possible, although a 1/8” slope is acceptable. It is also important to check local building codes and any HOA covenants. The table below compares the complexity and construction costs for some of the most popular bases for hot tubs.

  Complexity Construction Cost
Gravel Base Low $1 to $3 a square foot
Concrete Slab Medium $8 to $10 a square foot
Concrete Pavers Medium $10 to $17 a square foot
Deck High $20 to $25 a square foot
Prefabricated Hot Tub Base Low $8 to $14 a square foot

1. Gravel Base



Gravel Hot Tub Base

A gravel base is easy to make and strong enough to support any size hot tub, plus it offers excellent drainage and is easy to level. It should be between 4 and 6 inches thick of 3/4″ crushed stone, pea gravel moves too easily and doesn’t compact well. The gravel base should be larger than the hot tub so that it catches any spills or splashes.

To prepare the base, remove the grass and any other organic material. Dig down to make a level base into which to put the gravel or build a 2×4 or 2×6 frame with a lesser excavated depth.

A border will help keep the gravel base from spreading out and provide a mowing edge. Spread 2” to 3” of gravel depth, and compact and level it before adding more. It only needs to be compacted enough that it doesn’t leave a footprint when walked on.

Once the tub is in place, consider topping the crushed stone with a couple of inches of pea gravel. The pea gravel offers a more appealing look and is easier on bare feet.


  • Strong and durable
  • Easy and quick to make
  • Low maintenance
  • Good drainage
  • Inexpensive
  • Removable

  • Gravel is hard on the feet
  • Not very aesthetically appealing

2. Concrete Slab

Concrete slab for hot tub

Concrete contains Portland cement, sand, and gravel and can be used indoors and out to make a concrete pad for a hot tub. Concrete is solid, durable, sturdy, and long-lasting, but it can be slippery when wet.

It is common to make the pad larger than the hot tub base for protection from overflows or splashes and to provide a flat surface for access. The concrete pad should be 4” to 6” thick and rest on compacted crushed stone. It also needs to be level, so select a site that is reasonably flat.

To prepare the site, measure out the size of the pad and mark it with string, paint, or a hose. Remove the grass and other organic material and dig down 4” to 6”, making sure the bottom is level and free of loose material.

Build a 2×4 or 2×6 frame around the perimeter of the excavation and make sure it is level and secure. Fill the bottom of the excavation with 3” to 4” of gravel at a time and make sure it is compacted and leveled.

With the site formed and prepared, order the required amount of ready mix or mix your own. You may also want to have precut lengths of 1/2″ rebar to place into the concrete as it is poured. Pour 4” to 6” of concrete onto the gravel until it is level with the 2-by form frame.

Use a board to smooth or screed the wet concrete, and a float or trowel to polish the surface, or use a broom to roughen it once it sets up. You may also want to use an edger to round the concrete at the forms. The forms can be removed within a day or two of pouring.

Pro Note: To prevent crackling or flacking, either use a tarp or curing blanket to slow the curing process. Alternatively, moisten the surface with water 5 to 10 times a day for the first week, especially if the weather is hot.


  • Solid, strong, sturdy, and durable
  • Concrete can be colored
  • Low maintenance
  • Customizable

  • Expensive
  • Can crack or chip
  • Difficult to remove if the future
  • Should cure 28 days before filling hot tub

3. Concrete Pavers

Concrete Pavers

Concrete pavers come in a variety of sizes, thicknesses, and colors, so they can be used to make a decorative patio upon which to place a hot tub. The pavers can be placed on concrete, sand, or gravel, but they should be level where the spa will be placed. Pavers should be at least 2 inches thick and laid on a well compacted, supportive, level base.

Remove the grass and any organic material, and dig down 8” to 10”. Smooth and level the bottom of the excavation. Spread 3” of crushed stone on the soil and compact and level it, and then spread another 3” of stone and compact and level it too.

Spread 3” of sand on top of the gravel, dampen it, and compact it so it is smooth and level. Lay the pavers in the desired pattern, ensuring they are level and there are no gaps. Dust the pavers with sand to fill the joints between the pavers, and sweep off any excess.


  • Easy to build
  • Strong and durable
  • Aesthetically pleasing colors and patterns
  • Non-slip


  • Time-consuming
  • Higher maintenance
  • Expensive

4. Deck

Deck base

Decks are often used to provide easy access to hot tubs directly from a building and also offer a level base where the ground may be difficult to level. They are customizable and can support a hot tub or be framed around a hot tub, however, decks must comply with building codes.

Decks may be ground or near ground level, or they may be elevated. If they are attached to a structure, their support post footings need to extend below frost level. The further off the ground, the greater the structural requirements and expense.

Most decks are designed to support 40lb/ft² of live load and 10lb/ft² of dead load for a total of 50lb/ft². Depending on the size of the hot tub, the deck structure may need to support a 100lb/ft² or more, and require more calculations, materials, and money. However, only the section of the deck under the tub needs to be built that strong. The greater the elevation, the closer together the support posts and joists need to be, and the more important bracing becomes.

Existing decks may need to be reinforced or rebuilt to accommodate a hot tub, plus, they usually aren’t level. Many homeowners choose to place the hot tub on a gravel pad next to the existing or planned deck if the ground can be leveled, and build or extend the deck to or around it. However, it is important to ensure mechanical access points are accessible too.


  • Customizable and aesthetically pleasing
  • Electrical and other connections easier
  • Easy access from the dwelling
  • Ideal for unlevel ground


  • Very expensive
  • High maintenance
  • May require consultation with a structural specialist

5. Prefabricated Hot Tub Base – Ez Pads

There are numerous prefabricated hot tub pads; some have interlocking components and others are one solid piece. Most are fairly easy to install, and the bases range from $100 to $500 or more. Most can be placed on an existing patio of pavers or on grass, dirt, sand, gravel, or concrete. The important thing to remember, though, is that the base needs to be level, smooth, and well supported to ensure all warranty conditions are met.

Ez-Pads are one such product available in different sizes for use under hot tubs or spas but require some assembly. Manufactured of mold-blown HDPE plastic, a typical pad consists of four hollow 4’x4’ by 2” thick sections that are connected with butterfly straps and screws.

Although they can go directly on grass or dirt, it is recommended that the grass and any organic material be removed. Smooth, level, and compact the soil before covering it with several inches of 1/4″ to 3/4″ crushed stone, pea gravel, or sand that should also be compacted, leveled, and smoothed.

If placing the Ez-Pad directly on soil or grass, place garden cloth down first to prevent grass and weed growth. Most lawns are not perfectly flat, so spreading sand or gravel will help fill small depressions for a smooth surface. It is recommended that a border be used to keep the gravel or sand in place too.


  • Mildew, chemical, and slip resistant
  • No building permit required
  • Lifetime warranty
  • Portable and movable
  • Maintenance free
  • Easy to clean


  • Shipping costs
  • Only available in gray
  • Corners may curl or lift if unweighted
  • It still requires a smooth, level surface
  • Expand and contract with temperature

Do You Need a Foundation for a Hot Tub?

A hot tub can weigh several hundred pounds to more than a thousand pounds. A 6’x6’ 4-person hot tub typically holds 300 gallons of water and an 8’x8’ 8-person up to 675 gallons.

A gallon of water weighs 8.34 pounds and the ‘average’ adult 175 pounds, so that can add up to a lot of weight. That means a hot tub should have a base under it to help spread the load and prevent it from sinking into the ground.

It should be noted that a hot tub needs to be placed on a smooth level surface, which means some type of base preparation needs to be done. If the tub isn’t level, the waterline deviation will be noticeable, plus the jets should be below the water surface level.

It is recommended that the hot tub warranty section be checked to ensure requirements are followed so the warranty isn’t voided. Additionally, many building codes and HOA covenants have set requirements for hot tub installation, so check them out too.

What to Put Under an Inflatable Hot Tub?

A 4-person inflatable hot tub weighs around 90 pounds empty and between 1800 and 2800 pounds when 80% filled with water depending on its size. The base under the tub needs to be able to support the weight. Concrete pads, paved driveways, pavers, the ground, sand, or even crushed stone or gravel are good choices.

Most decks can handle combined loads of 50lb/ft². A 6’ square inflatable hot tub with 210 gallons of water and 600 pounds of people in it is almost 68lb/ft². So, unless reinforced, a deck isn’t a good choice.

An inflatable hot tub can be used year-round, is portable when empty, and can be placed on almost any smooth, reasonably level, supportive, stable surface. To protect the bottom of the inflated tub, it’s recommended that a protective material be placed under it to prevent punctures, tears, abrasions, or other damage. The softer and smoother the material between the inflated tub and the base or ground, the more comfortable it will be on feet, knees, and bottoms.

Interlocking foam tiles, reflective bubble insulation, carpet, or foam underlayment are excellent choices to put under an inflatable hot tub to protect it from damage. One of the best choices I’ve experienced is pink or blue rigid insulation. It doesn’t compact much under the weight, offers great protection, and is soft on the feet, bottom, and knees.

Some other options are 6 to 20mil plastic sheeting, tarps, or even boxboard with staples removed. They will protect against abrasions and tears, but don’t offer much in the way of padding.

Can You Put a Hot Tub on Grass?

Can You Put a Hot Tub on Grass

Most hot tub warranties, building codes, and HOA covenants require a permanent hot tub to be placed on a smooth, stable, supportive prepared base. Grass, although it may feel supportive, isn’t usually compacted, smooth, or stable, and it retains moisture which can damage the hot tub framework. Plus, the grass is the home of worms, insects, frogs, and rodents, so placing a permanent hot tub on grass is strongly discouraged.

Grass and bare ground don’t provide a good base for any hot tub. However, inflatable hot tubs can be temporarily used on grass but should have a protective barrier placed down first.

It should be noted, though, the hot tub will flatten the grass and leave a depression in the ground which may cause problems in the future. Additionally, it is more difficult to keep grass clippings and dirt out of the hot tub if it is on the grass or ground.

How to Level Ground for Hot Tub

Once you have selected the site for your hot tub, measure and mark the location. It is common to make the area larger than the tub to allow for splash outs and to support steps and a foot wash bucket.

Once marked, use a string level or level on a straight board to identify the slope of the ground in different cardinal directions. This will identify where the ground needs to be lowered or raised, and by how much.

Gravel, crushed stone, and sand bases typically require a border to keep them from spreading, which can be used to provide a level frame reference when making the base. Concrete requires level forms to contain the pour, which can also be used to level the ground and gravel underneath.

Pavers or paving stones usually require a compacted crushed stone base covered with tamped sand, and may even have a border too depending on the elevations, and aesthetics.

For most bases, it is necessary to remove the grass and other organic material and remove 4” to 10” of soil depending on the type of base being constructed. Smooth the soil as levelly as possible and remove any loose material.

Tamp or compact the soil and then spread 2” to 3” of crushed stone and compact it. Spread another 2’ to 3” of gravel, and compact it so it is level and doesn’t show a footprint when walked on. A level crushed stone base can be used directly for the hot tub or for a sand, concrete, or paver base.

What Is the Best Base for a Hot Tub?

Before installing a hot tub, check with your local building department and HOA for any restrictions or requirements. Additionally, check the warranty for the types of bases acceptable for your hot tub. You want the base to last and meet all requirements.

It is interesting to note that concrete pads or slabs, pavers, and many prefab pads commonly require compacted crushed stone to provide a strong, stable, solid, level base underneath. Even wooden decks typically have gravel spread under them. So, if compacted crushed stone is required to form those bases, then logically, it would be the best base.

Compacted crushed stone or gravel is the best base for hot tubs, and it is DIY-friendly. It is strong, stable if it has a border, durable, solid, offers excellent drainage, and won’t crack. It is inexpensive, quick, easy to install, compact, and level. It is also easy to place electrical conduits or plumbing in the gravel too. Plus, it can easily be removed when no longer required. Crushed stone can also be topped with pea gravel or other materials to improve its aesthetics.

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