Having a sturdy level base for your hot tub is vital to ensure your hot tub functions correctly and does not get damaged. Many dealerships will recommend tradespeople to build the foundations for you, and if you are not confident in DIY, then this is a good option for you. However, building a base for your hot tub is straight forward, and by doing this yourself, you can both save money and construct the base that suits your yard best.
In this article, we look at all the different hot tub bases with details on how you can build them yourself. I will also include some handy tips that will save you money and time! If you are looking to build a base for your inflatable hot tub, you do not need such a sturdy base, but will have to think about heat insulation; I have explored this at the end, so you can scroll down and skip the bulk of this article.
What is the weight of a hot tub?
In the specification of your hot tub, the manufacturer will detail the weight of the hot tub when it is filled with water. This weight will vary between 3200lbs and 4500lbs depending on the hot tub design. (For example, the Cotswold hot tub I reviewed weighs 3370lbs when full.)
After you know the weight of your hot tub when full of water, you need to add the maximum number of people that may be in the hot tub. For a standard 5-6 seat hot tub, the worst case scenario is seven people. The average person weighs 185lb, so the maximum added weight is 185 x 7 = 1295lbs
Is a hot tub heavy…?
A total of between 4495lbs and 5795lbs may seem like a lot (and it is if you were trying to lift it!) but spread out over 49 square foot of a hot tub; the weight is only around 100lbs per square foot! In engineering terms, this is light, so when we build our base, we need to concentrate on getting it level rather than making it super-strong!!
Deciding where to build the hot tub base
Choosing where to construct your hot tub base needs some serious consideration. You will need to be able to access the hot tub all year round so it will need to be near to your home. You will also need room around the hot tub to service it, and you will need space to open and shut the lid.
The area needs reasonable drainage so that you are not stepping in muddy puddles before entering the hot tub. Also, as you and your family exit the hot tub, you will be surprised by how much water drips off you and this will need to soak away as well.
The best position for your hot tub
The perfect hot tub position will not be overlooked by the neighbours and will be landscaped into the garden using screens and potted plants. It will look like a little oasis and will complement its surroundings.
Beware of overhanging shrubs or trees that will drop leaves, flowers, or pollen into your hot tub. Extra contaminates mean that your filtration system will need more maintenance.
Finally, your electricity and water supply will need to be close to the hot tub. This tip is obvious, but I needed to mention it anyway!!
Concrete hot tub base
Concrete has been used to build hot tub bases for years, and as a building material, it is very versatile. It is easy to make level and will out-live your hot tub if built correctly. The disadvantage is it can be expensive, and it is not very environmentally friendly as some of the other options detailed in this article.
Building the frame for the concrete
First, you will need to make a timber frame to set your concrete mix in. The size of the base will need to be larger than the hot tub. I recommend at least a foot longer in each direction.
You will then need to remove any turf and topsoil. I would dig down the same thickness as you are going to make the base – five inches will be sufficient. Having the top of your base level with the surrounding soil makes it easier to position the steps where you need them.
If your base is under 10 foot in each direction, you will not need expansion joints so you can mix and pour all in one go.
What ratio of cement to aggregate should you use for the hot tub base?
As we said before, you do not need to make the concrete mix too strong, so mix to a ratio of 6 buckets of ‘all-in aggregate’ to one bucket of cement; a 1:6 ratio is perfect. I have heard people suggest that you need a ration of 1:3. This ratio is the same strength used in foundations to build houses! We are not building a house, just a level piece of ground to put our hot tub on!
Using all-in aggregate will also save you time as the sand is already mixed in, and the ratios will be excellent for what we are building.
To calculate how much all-in aggregate you will need to use, multiply the length by the width, by the depth and then divide by 27 to get the cubic yard or multiply by 0.0283 to get cubic meters. Then add an extra 10% to be sure you have enough
I find the math too complicated, so I use one of the many websites that will do the calculation for you. I have linked one below, but if you google concrete calculator you get pages of suggestions!
Top Tip: Buy a cement mixer on eBay!
Mixing this much concrete by hand is too much hard work. Buy a cheap mixer on e-bay and then sell it afterwards. Look out for auctions that are ending on random days or when events like the Super Bowl are on. There will be fewer people bidding, and you may get a bargain. When you go to sell the mixer, make sure the auction ends on a Sunday evening when there is likely to be more people bidding.
Gravel hot tub base
Building a gravel base is the easiest option, but some say it is not cosmetically pleasing! I think they look fine and if you do not like the color of the gravel that is exposed, then you can buy ornate gravel to cover it. The main advantages are gravel bases provide excellent drainage, and they are cheap to install. Out of all our options, this is also the most environmentally friendly solution.
Unlike the concrete base, the wooden supporting structure will have to remain, so it is vital that this is made from pressure treated wood, and that any cut ends are treated with a wood preserver. Depending on where you live in the world, this frame will last between 2- 4 years. The problem is the underside of the wood is in contact with microbes in the soil, and they will eventually eat the wood.
Building a gravel hot tub base
The process is initially the same as making a concrete slab. You will need to remove any turf and topsoil and build a timber frame. Use pressure treated wood and secure with 10/12 inch galvanised lag screws; the type used to construct decking. 12inch nails will also work but will make the job harder, in my opinion.
Before you lay the gravel, put down a water permeable landscaping cloth. This cloth will stop any weeds growing up through the gravel. Use a medium/course gravel (crushed rock), making sure it is packed in tight. You can finish with pea gravel to get the base perfectly level. However, if you have domestic cats that visit your garden, do not leave the pea gravel exposed or they will use it as their litter tray, which detracts slightly from the hot tub experience!!
Prefabricated hot tub bases
There are a number of prefabricated hot tub bases on the market, and they fall into categories.
Plastic lattice bases
These generally come as 12inch tiles that you join together to make the size of base you require. They are marketed along the lines of you can assemble them anywhere without any preparation. Although this is true if they are placed on a completely flat surface, the bases work and look better if you put a little work in.
The plastic lattices can be used without gravel, but I think they look better with gravel. The gravel also provides extra strength and shields the plastic from the sun’s UV rays. Unlike the wooden joists we used above, they will last for many years.
Look for products that are made from recycled plastic. They are as good as non-recycled and are of course, better for the environment.
Building a base with pre-fabricated plastic tiles
Remove any turf and dig down to the same depth at the plastic lattice – typically only a couple of inches. As with the gravel base, I would lay the water permeable landscaping cloth to stop weeds growing. Once the plastic tiles are in place, fill with gravel before installing the hot tub.
Another option would be to install the hot tub and then fill the exposed lattice with a mixture of topsoil and coarse sand. You could then sow grass seed, giving the impression that the hot tub was just put on the lawn. The sand will ensure there is adequate drainage around the hot tub, so puddles that could damage the hot tub’s cabinet shouldn’t form. You could do a similar thing with wooden bark or decorative stones.
The other type of prefabricated base is a solid plastic base
These are designed to lay on flat turf, compact soil, gravel or paving, and help distribute the weight of the hot tub evenly. As with the plastic lattice tiles, the manufacturers claim they will mean you have less work to do, as you do not need to prep the ground. This claim is only valid if the soil is entirely flat; if this is not the case, then you will have to level the ground first.
I do not recommend you place your hot tub on flat turf or compact soil unless the drainage is impressive. When people exit the hot tub, a lot of water drips off of them, which will cause puddles and potentially damage the surrounding lawn.
If you want to give the impression that the hot tub is directly on the lawn, then I would recommend you use the plastic tiles, detailed above, with a sand/soil mix that will aid the drainage.
Installing the solid plastic base
To get the best out of this product, I would remove the topsoil from the area that I wanted to position my hot tub. I would line the hole with permeable landscape cloth and fill with crushed rock. This cloth will stop any drainage issues and will allow us to get the surface completely flat before we cover the gravel with the solid plastic base.
Placing the Hot tub on a patio
Placing a hot tub on an existing patio is a sensible, cost-effective way to install your hot tub. Patios are generally constructed at the rear of a property, which is ideal for easy access to your hot tub. You are more likely to use the hot tub if it is easily accessible.
The winter is the most fabulous time to use the hot tub, but you need to take some precautions to make sure you stay safe. Having your hot tub on the patio will make jobs like removing snow from the hot tub cover and ensuring clear passage to the house easier. For more details on winter hot tubbing, click here.
Disadvantages of placing your hot tub on a patio
Unfortunately, many patios are constructed at a slight incline to allow for the water to drain away. If this is the case, placing your hot tub on this surface may damage it in the long term.
Patios that do not have an incline tend to get puddles forming after rainfall. If your patio does this, you could use a plastic base, which will raise the hot tub out of the water, so it is less likely to be damaged.
Paving stone base
You can build a paving stone base for your hot tub; effectively building the hot tub a patio! I am not a fan of this as the work involved is more than gravel or even a concrete base, and the result may not be as good. Paving stones are more likely to move independently of each other, making the base uneven.
Hot tub decking base
I think hot tubs look fabulous on wooden decking. It softens their appearance, and, when built well, makes the hot tub blend with the landscape. Building simple decking is straight forward even for a novice DIY enthusiast.
Intricate decking designs, where the hot tub appears partially sunk with multiple raised decking areas, will need to be at least planned by a professional structural engineer. However simple flat decking designs can be designed with a ruler, some paper, a pencil and a measuring tape!!
Building a decking base
When I constructed my decking, the planning took a couple of hours, and the decking was built over two weekends. It took a long time because it needed to fit around the rear of the house and around four trees! A simple eight-foot square decking construction can be quickly completed in one afternoon by one person with the correct tools.
Getting the correct spacing of the joists, beams and footings is vital to the stability of the decking. The resource I used to help me plan out my decking was www.decks.com. They have thousands of articles to help you build your decking. They have some fancy builds, but if this is the first decking you are making, maybe keep it simple!!
Tips for building a decking hot tub base
The primary advice I can give is to get the frame right. Many people are in a rush to start to lay the decking planks, but spending the time to get the base flat and secure is the most vital part. I over-engineered mine, having more footings than required and putting the beams closer than needed, but what this has resulted in is incredibly durable decking!!
The other tip that will save you so much time is to use an electric drill and have at least one spare battery. If possible, it is handy to have two drills. Having two drills will stop you having to change the drill bit for the different screws.
Inflatable hot tub base
Inflatable hot tubs should be installed on flat surfaces like solid hot tubs. However, a slight incline 1-2 degrees is not a problem. My first hot tub was an inflatable, and I placed it on some existing paving, which was on a very slight incline to allow for rainwater to run off. The slope caused no issues whatsoever.
If you are planning to use your inflatable hot tub in cold weather, you may want to think about a base that is insulated. Inflatable hot tub manufacturers sell a base that has some insulation qualities, but it is mainly designed for comfort.
There are thick rubber tiles on the market that make an excellent insulated base, but before you go and spend a lot of money on them, think about how much they will save you in energy. I would suggest, not a lot because most of the heat is lost from the surface of the water so you might be better off buying something to insulate that more effectively. I have detailed some ideas for this in the following article – cold weather hot tubbing tips!
What is the best base for a hot tub?
The best base will depend on where you are planning to place your hot tub and what your budget is. The most cost effective is a crushed-rock / gravel base, and I think this, combined with the plastic tiles, provides the best long-term solution.
If you want any more information, please feel free to contact me directly. If you can add to the conversation, leave a comment below!
Enjoy your day!