The full hot tub with bathers can weigh up to 5000 lbs. (~2 tons). Choosing a durable and solid base is a must to prevent it from cracking.
While selecting a hot tub foundation, you might get confused with so many options such as concrete, gravel, pavers, deck, or spa pad. To make your decision easier, we will cover the pros and cons of each spa base and provide installation tips.
A good hot tub base should be solid and durable. Below we prepare a short comparison table between the most popular types of foundations.
|Concrete||Pavers||Gravel||Wooden deck||Prefabricated pads|
|Efforts for setting up||Medium||Slightly high||Medium||High||Low|
|Go to the detailed review||Go to the detailed review||Go to the detailed review||Go to the detailed review||Go to the detailed review|
Hot tub base: essential things to know beforehand
There are TWO aspects you should understand and remember while thinking of the hot tub base.
- How much pressure does a full hot tub make per square foot?
You should know it because the bearing capacity of different materials varies. You need to be sure that the base can handle the pressure of a full jacuzzi with bathers.
The calculations are straightforward. You should know:
- Wempty — weight of Empty Hot Tub (depends on your model)
- 1 Gallon of Water = 8.34 lbs (3.78 kg)
- Vw — the maximum volume of water in the hot tub
- Wperson — average Weight of Person = 185 lbs (~84 kg)
- N — max. number of bathers
- Shot tub — square Feet of Hot Tub = Depends on your model
Here is the formula:
(Wempty + Vw8.34 lbs + Wperson N)
2. Foundation should be levelled
This is a golden rule. In case the foundation is not levelled you will get many issues.
- The hot tub may crack because of the uneven distribution of the weight.
- The water level is off which makes sitting uncomfortable.
- It will invalidate the hot tub warranty.
You should use a 3-4’ level to check the evenness of the foundation.
An accurate and easy-to-read 4’ level
Concrete foundation — a classical and durable solution
Pros & Cons
- Strong enough to support the hot tub of any weight
- Customized size
- Low maintenance efforts
- Expensive (around up to $10 per square foot)
- Before placing the hot tub, the concrete should cure for 28 days
- Can crack
How to install a concrete base
As a rule, the minimum thickness of the concrete should be 4-6” (10.16 cm) to support the weight of the full hot tub. You can also add some reinforcement to the slab, however, in most cases, it is not necessary.
The most vital thing about a concrete slap is that it should be levelled. For this reason, many concrete patios are not suitable for setting up hot tubs. They were built a little pitched for better drainage.
📌Pro Tip! After pouring concrete, you should keep it moisturized for the first several days to ensure a proper cure. You can do it in two ways:
- One way is to hose with water 5 and 10 times a day for the first 7 days if the weather is warm. It is best for those who work from home and have free time to do it on a regular basis.
- A second, and much easier way, is to use polyethylene sheeting or special concrete curing insulation blankets to slow down water evaporation. It’s the best for people who spend a lot of time away from home. Just lay it on your concrete foundation and wait a few days. Based on my experience and 100+ user reviews, I recommend this blanket:
- Triple layers construction for maximum heat and moisture retain
- Rust-resistant aluminum grommets for anchoring and staking
How to improve the appearance of a concrete slab?
The sad truth about concrete slabs is that they are not very attractive and barely suit every exterior.
You can improve the look of your slab with deck tiles. You can use it both around the hot tub and put it underneath. One more advantage is that it gives a better feeling to your bare feet while standing on them.
Deck tiles have a different texture and look. Here are our top picks that will make your slab look better. They are also strong enough to support the weight of the hot tub.
| – Easy to set up and sturdy|
– Water-proof and UV-resistant
– Easy to clean
– Can be cut with an oscillating blade
– To cover an 8’*8′ area: 3 packs of 20 tiles
| – Slip-resistant|
– Can be cut with a saw
– Good looking
– Can deform under the direct sunlight
Gravel base — an easy-to-make and cheap hot tub foundation
Pros & Cons
- The cheapest option ($1 – $3 per square foot)
- Easy to set up (3 hours to do all)
- Doesn’t crack (compared to concrete)
- No waiting time (compared to concrete)
- Good drainage
- Suitable for long- and short-term solutions
- Can be hard for the feet
- Not the best-looking option (depends on your tastes)
How to install a gravel hot tub pad
Gravel base is a strong and easy-to-set-up material to support your spa. Actually, it proposes advantages that non-other foundation has.
There are several rules to follow while making a gravel hot tub base:
- Leave a space of a few inches around the hot tub to prevent splitting the water on the grass and for aesthetics.
- You should dig not less or more than 6” (15 cm). Otherwise, the base would have bad drainage and be unstable. Remember! The dug hole should be levelled.
- Fill the hole with medium-grade construction gravel (¾ crushed stone). For the last 2” (5 cm) you can use pea gravel for a pleasant look.
- Compact the gravel every few inches and level it!
📌 Pro tip #1! You can understand that the gravel is compact enough when you can walk on the base without leaving a footprint.
📌 Pro tip #2! You shouldn’t use only pea gravel as a base. It is not strong enough to support the hot tub. Put medium-grade gravel under and then add some pea gravel above.
Pavers — strong and good-looking base
Pros & Cons
- No waiting time (compared to concrete)
- Many design variations (patterns, colours, shapes)
- Easy access to electrical or plumbing lines if they go under the hot tub.
- Resistant to efflorescence
- Cost-effective (Starts from $3-6$ for concrete pavers, with the average around 10 – $17 per square foot, and can reach up to 30$ for flagstone)
- Can be a little time-consuming while laying them down
How to install a paver
Pavers are another popular hot tub foundation. It is sturdy and looks fantastic.
To lay down a paver, you will need to use either sand and gravel or a concrete slab as a base.
As the first option is more cost-effective. Here are some points to make it right.
- Dig into the ground for about 12”.
- Fill 3” with sand. Level it a little, wet it, and compact it to make it flat, and hard.
- Fill 3” with gravel. Compact it to make a level surface.
- Put pavers on it. Lay it down with no gaps and check over time.
- If you get gaps or unleveled surfaces, take a few steps back and redo. The final result will be worth your time.
- After you lay down all pavers, fill minor gaps with sand to fix the pavers in place.
Bury in mind, that selected pavers should create an ideal flat and leveled surface to install the hot tub securely.
📌 Pro tip #1! The common material for the pavers is concrete, cobblestone, brick, flagstone, and rubber. All of them have features you might need to know while selecting.
- Concrete is the cheapest paver and is more durable compared to a concrete slab. If it is coloured it can fade due to sun exposure.
- Cobblestone is hard to work with and costly, however, very durable.
- Bricks don’t fade and are extremely strong (can hold up to 12,000 pounds per square foot).
- Flagstone is durable, good-looking, and stays cool under the sun, however, it is expensive.
- Rubber pavers are maintenance-free and non-slip. They are made of recycled material.
📌 Pro tip #2! The ideal thickness of the pavers to support a hot tub is around 2-3” (5 cm).
Truegrid Pro Lite Pavers
The world-strongest gravel grids made the gravel construction even more solid. Truegrid Pro-Lite Pavers are designed for hard-duty use and can easily handle the hot tub weight even with 8 bathers.
It is made from recycled plastic, so it is a nice option if you care about ecology. To cover 8’*8’ (64 square feet), you need to get one pack of the Truegrid Pro-Lite Pavers.
For installing the Truegrid, you should first put 3-4” of cracked stones and level it. Then put the interconnected grids onto it.
After that, you can put the hot tub just on the bare grid. However, most users prefer to fill it with pea gravel to make it look and feel better.
Wooden deck — luxurious solution
Pros & Cons
- Looks luxurious
- Usually placed just near the home that increases your comfort and privacy
- The reinforced deck can handle 7-8 person hot tub
- The most expensive option (around $15 – $30 per square foot)
- You need to consult with a specialist to be certain the deck can support the weight of the hot tub.
- Can rotten
How to build a wooden base for a hot tub
The main rule about placing the spa on the deck is that it should support more than 100 lb per square foot. The bearing capacity depends on the material, joist spacing, joist overhang, soil type, and other factors.
It is a lot of math and calculations. However, there is a simple rule for a rough evaluation:
📌 Pro tip! If the new deck is not higher than 2 feet above the ground, in most cases it can handle the hot tub weight and doesn’t require reinforcing. If it is higher than 2 feet, it will need additional support. Usually, posts should be no more than 30 inches apart.
Reinforcing the deck is not a DIY project, especially for beginners in construction and building. You should at least consult or hire a professional to make sure you will get what you want.
Additionally, if you want to place the hot tub on the existing wood deck foundation, you should check the followings:
➡️ Condition of the existing deck. Is it old, broken, has splintered, or shows signs of rotting?
➡️ Level. The surface should be flat with no imbalance. Check it at the 3-4 feet level.
➡️ Location that will ensure free access to the motor for service.
Prefabricated hot tub base — time and effort saver
All previously reviewed options require some manual work or have waiting time or risks with getting an uneven surface. If you don’t want anything of this, the prefabricated hot tub foundation is for you.
It is made from hard plastic and can easily support the weight of the filled hot tub.
Our top pick from Amazon among hot tub bases is a Confer Handi Spa Pad.
Pros & Cons
- Durable and waterproof
- Less manual work
- Moderate price ($8-15 per square foot)
- Does not require a permit for placement
- No waiting time
- No hard calculations
- Appearance (depends on taste, but it is not so stylish as other options)
- No size adjustability: most spa pads are quite large, so it is hard to adjust the size just for the size of the hot tub.
Confer Handi Spa Pad
The most affordable spa pad
1 pack of 6 pieces covers 8’*8’ space
There are two things to note about the Confer Handi Spa Pad.
- It should be put on a levelled surface. According to the installation manual, you should place the pad on the 1’-2’ tamped sand.
- The connectors between the pads can frequently pop out when you will try to turn the assembled construction over.
Lifehack! You can use drywall screws to secure stable connections.
Hot tub base for the inflatable hot tub
Inflatable hot tubs weigh less than hard-surfaced ones. They also have no frame, so the requirements of a perfectly even foundation are not so strict.
However, if the base isn’t level, it will cause discomfort for bathers as the water level will be higher on one side. Moreover, the concentrated pressure on one side decreases the hot tub’s lifespan.
One more factor to consider is that many owners of inflatable hot tubs tend to buy a solid option over time. Preparing a good base will save you many nerves and time in the future.
The perfect base for the inflatable hot tun is solid, and smooth, with no pecky and sharp edges. The latter can damage the vinyl. Below you can find the list of suitable bases:
- Wood deck. As we wrote above, be sure that it can support the weight of the full hot tub with bathers
- Concrete. Solid, but you need additional insulation with a mat or flooring protector to make sitting in the hot tub comfortable and prevent heat loss.
- Existing patio or paver base. A fine option, just make sure that the pavers have a good foundation to support the weight of the hot tub. The same as for concrete things about good insulation.
- Spa pad. They are specifically designed to support the hot tub weight.
- Gravel base. Not the best option. It should be perfectly levelled and you should use an extra-thick pad to avoid damage from stone edges.
Placing an inflatable hot tub on the grass
In contrast with solid-frame hot tubs, inflatable ones can be placed on the ground. However, you should consider this option only for a short-term stay.
If you want to set up the tub for longer than a month, it is better to select more solid construction.
The ground is rarely even and not strong enough to support the hot tub. After some time you will end up with an uneven surface. It will shorten the lifespan of the hot tub. Moreover, the hot tub will damage the grass.
❗ Grass is a bad insulator, so you will lose a lot of heat from the bottom.
Whatever base you select, you need to place it on the protective and insulating layer. Usually, it is made of synthetic foamy material. On the market, you can find both a specifically designed mat for a hot tub and some good and cost-effective alternatives.
CosySpa Hot Tub Flooring Protector
If you are looking for a pad that perfectly matches the footprint of the round hot tub then the CosySpa Hot Tub Flooring Protector is your favourite. It is suitable for placing a hot tub with a diameter of up to 80.7 in (205 cm).
Foam flooring tiles are easy-to-assemble and do what they suppose to do. The product makes sitting in the hot tub comfortable and provides insulation.
The product goes in two thickness options 1/4″ and 1/2″. The latter one is better for more insulation and durability.
ProsourceFit Extra Thick Puzzle Mat
If you look for better protection of the hot tub button and want to save money on preventing heat loss then you can buy a thicker alternative.
Many owners use ProsourceFit Extra Thick Puzzle Mat to protect their hot tubs from hard surfaces as this product is made of durable EVA foam and goes in two thickness options 3/4” and 1”. Moreover it is waterproof.
Compared to the CosySpa Hot Tub Flooring Protector you can also adjust the size of the pad and cut through it easily. One pack of 72 pieces is enough to cover 8’*8’ area.
Choosing the base type and its construction are aspects you should consider before installing the hot tub. The main rule for any base is to be solid and level to support the hot tub weight and prevent cracking.
Along with traditional concrete slabs, some options can save you time and money. For example, gravel and pavers are cheaper and give good drainage. A wooden deck is an elegant and comfortable solution. Prefabricated spa pads save you time and money on construction.
If you prefer an inflatable hot tub, then you can place it on smooth ground for a short-term stay. However, it is better to prepare a sturdy base to avoid any problems. Bury in mind, that you will need to buy a mat to protect the bottom from damage and decrease heat loss.
🥇 What is the best hot tub base?
It depends on what you expect from the hot tub base. If you look for something simple and durable then you should choose between a concrete or gravel base. If something authentic then the pavers or wood deck is your favorite. If you don’t want to put much effort and time into construction then the prefabricated base is a must.
🤔 What to put under an inflatable hot tub?
You can put a hot tub on concrete, pavers, wooden deck, prefabricated bases, and gravel. If you look for a short-term placement you can set it up even on gravel. Bury in mind that you need to put the inflatable hot tub on the protective and insulation mat made of foam.
☘️ Can I put a hot tub on bare ground?
No, one exception is inflatable tubs for a short-term stay. The ground is not solid enough to support the weight of the hot tub without deformation. While the surface becomes uneven it causes additional pressure on one side of the hot tub frame. As a result, it can crack the spa and void the warranty.
⛱️ Can I use sand as a base for the hot tub?
Sand is not the best option for the hot tub base. It is easily displaced and washed out with water and winds. As a result, the surface becomes uneven which may crack the hot tub.
🙂 Can I put a hot tub on the existing patio?
Only in some cases. Firstly, you should be certain that the place is leveled. Many patios are built a little pitched for better drainage. This is not acceptable for a hot tub. Secondly, the foundation of the patio should be strong and thick to support the weight of the hot tub. If you have any doubts, it is better to make a new base.
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