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How To Level Ground For An Inflatable Hot Tub – Simple Guide

Have you noticed a slight slant in the water level in your hot tub? You may have thought that the ground you’d installed your spa tub on was straight as an arrow, but over time, it’s not uncommon for the earth to shift under the extra weight of all that water. 

You might not have even got round to installing your hot tub spa yet, in which case, you’re here just in time to learn how to level the ground for an inflatable hot tub.

In this article, our team will guide you through the do’s and don’ts of safe hot tub levelling, from the materials you’ll need to the calculations behind the job. We’ve covered everything you need to know about creating a level surface for your hot tub, so let’s get stuck in.

The Best Way To Level A Portable Spa

planks of wood

So, now we know why it’s essential to level a hot tub, let’s get on with the best ways to get the job done. 

There are a few hot tub levelling options to choose from, depending on whether your hot tub spa has already been installed or you’ve got a new hot tub to fit into place. We’ll go over each below and walk you through the process. 

Already Installed / Without Moving

If your hot tub is already in place, creating a level surface will require shims or a spa leveller to make up for the gradient at which the ground is sloped. Whilst you won’t need to move your hot tub too much to get shims into place, it will be easier to pop them under an empty spa, but if you want to go down the spa leveller route draining and shifting, it will be necessary. 

Can you put shims under a hot tub?

If the slope of your hot tub is an inch or less, support shims are your best option to level the hot tub.

You can buy heavy-duty plastic shims specifically for this job or make your own wooden shims from a pressure-treated plywood sheet and wood wedges. 

This method is recommended, so it’s not uncommon to find “shim points” lining the side of some hot tubs.

Shift your hot tub a little and place a few shims along the low end of the base about 1ft apart, then place your plastic or plywood sheet over the top and attach it to the shims with screws. We recommend popping a spa pad over this platform to protect the base of your hot tub.

With your plastic or wood shims in place, you can now slide your hot tub back over the platform and you should have an excellent level base for your hot tub! 

Do I need a spa leveller?

A spa or hot tub leveller works to fix the gradient of any hot tub base and help level a hot tub, though it’ll be particularly effective at levelling a slope of more than an inch. These products consist of a secure platform with several holes to allow airflow under your spa, and at least four adjustable feet that can be used to form a level base.

To use this tool appropriately, you’ll need to know your slope’s gradient, so pop a spirit level on the platform and adjust the feet until it’s level. Once you’re confident that the spa leveller is dialled in, move your drained hot tub out of the way to put the leveller in place.

It’s a good idea to pop a spa or hot tub pad over the leveller to protect the base of your hot tub. Then you’ll just need to slide your hot tub back on top of your new base; now, you should have a perfectly level platform for your spa to sit on! 

Not Choose a Support Base Yet?

This job is made even easier if you’re installing your first hot tub or creating a level base for a brand new hot tub. Hot tub installation can be tricky but at least you won’t need to faff around draining your hot tub or spa tub or shifting it to install shims underneath the base.

Follow one of the two methods explained and install your hot tub directly onto your new levelled ground! This page discusses the different options and what you can put under an inflatable hot tub.

How To Build A Level Platform For A Hot Tub

hot tub sat on decking

Creating a custom platform can be a good option if you want a bespoke base, whether that’s a deck, stone patio or something else. You can design it to look a little nicer than a leveller or plastic shims, and you can fill the base with a weighted material to provide a little more stability for hot tubs, though doing this will require a little carpentry knowledge! 

1. The calculations

Levelling your hot tub is a great idea, but first of all, you’ll need to do a few calculations to work out the dimensions, the cost of construction and the materials required for your new platform; these will include:

  • A slope measurement to determine how uneven the ground is
  • The length and width measurements of your hot tub
  • The framing materials you’ll need, including 2×4 boards of pressure-treated lumber and screws
  • The amount of sand or gravel needed to fill the entire box

2. DIY platform for an inflatable hot tub

Use your 2×4 boards of pressure-treated lumber to build a hollow wooden box that measures one inch wider than your hot tub. The bottom boards should be tapered to the gradient of your sloped surface so that when you lay the box down, the top boards create a level platform. 

You’ll need to use pressure-treated lumber for this job, as your finished box will need to withstand the outdoor elements and the moisture from your hot tub. We also recommend drilling a few holes along the lowest boards to allow any rain or hot tub water to drain away safely. 

3. What to fill it with?

Gravel or sand will be your best bet. A hot tub gravel base is a great option as these materials are inexpensive, provide great stability, allow water to drain away, and can be moved if you want to shift your hot tub later. Just fill the box with one of these materials up to about an inch from the top.

If you’re confident that you’ll never want to move your hot tub again, filling the box with concrete can also be an option, though this is a more permanent solution as once that concrete sets, it’s not going anywhere! 

4. Finishing touches

Now that the hard work is done, you might want to paint or stain your new platform to give it a good finished look! 

This step isn’t necessary, but choosing a complementary colour to your hot tub can make the installation look more professional, and a layer of paint or stain will help further protect the wood from the elements and water from the hot tub.

Inflatable Hot Tub On Sloped Patio or Uneven Concrete

To level out sloped concrete, you’ll need to create a new concrete pad over your existing structure surfaces using self-levelling concrete. To start, clean the existing concrete pad with a chemical cleaner, then rinse any dirt from the surface or foundations.

Wooden Base

Now build a wooden frame around the area using 2×8 lumber boards secured with nails at least 2 inches thick. The inside of the boards should be sprayed with vegetable oil to prevent the levelling compound you’re about to apply from sticking!  

Use wooden stakes placed 2ft apart around the outside of the boards to hold the frame in place, then prepare and dilute a concrete bonding agent to be applied to the existing concrete with a paintbrush.

With the bonding agent applied, you can now mix your self-levelling concrete in accordance with the instructions on the packaging and pour the mixture into your wooden frame. 

Once poured, allow time for the concrete to level and smooth the edges with a trowel. Once dried, you should have a new level concrete pad for your hot tub! 

Can a hot tub be on a slight slope??

Ideally, you don’t want any degree of sloping under your hot tub, as even a slight gradient can eventually cause tears, cracks and breaks in the hot tub or spa’s shell. If your water line looks even a little wonky in the hot tub, at least consider installing shims under the base to prevent any issues! 

How To Level Out A Hot Tub Installed On Pavers

If you’ve chosen a paved base for your inflatable hot tub, it’s a good choice. You may still need to tweak levels. To do this, you’ll need to ensure that the pavers are not raised, are smooth and interlocking, and are set on a level sand or gravel base to help evenly distribute the weight of your filled hot tub spa.

  • Create a sand or gravel base a little larger than your hot tub spa at the installation site
  • Compact and level this base using string lines to check there’s no gradient
  • Place the pavers down and make sure they’re level.
  • Install your hot tub on top of your new levelled base

Does an Inflatable Hot Tub Have To Be Perfectly Level?

There are several reasons why installing hot tubs on sloping concrete or any other uneven surface is a bad idea. For starters, you’ll have a wonky water line which could mess up your air jets, and the uneven weight distribution can cause cracks and tears in your hot tub’s shell. 

Let’s take a closer look at why you’ll want a flat surface for your spa tub and how to level a hot tub correctly.  

Weight distribution

Possibly the most significant reason you’ll want a perfectly level base for your hot tub is so you can distribute its weight evenly. A sloped or uneven surface will lead to more pressure on a smaller area of your hot tub spa, increasing the likelihood of the hot tub shell fracturing or tearing.

A filled hot tub can weigh as much as 2500kg, and that’s before you add in your guests, so hot tub manufacturers have designed these things to spread the stress of all this weight evenly across the entire shell, which can’t be done if the base isn’t perfectly level! 

Safe usage

An uneven surface can damage your hot tub and make it unsafe for you and your guests to use. Picture yourself trying to safely get out of a wonky hot tub and doing your best to not slip over on wet, sloped concrete slabs; that’s an accident waiting to happen! 

You’ll also end up with one end of your spa hot tub being deeper than the other, which can pose a serious risk of drowning if you have kids around, so it’s a no-brainer that a stable surface is a must if you want to stay safe whilst enjoying your hot tub.

Hot tubs are noisier on uneven ground.

If your hot tub has a massage system, the air jets must be below the water line to work properly. You might think these things are noisy enough when they’re bubbling away, but take it from us, they’re at least twice as loud when there’s no hot tub water to muffle the sound.

The uneven ground also poses an issue for your hot tub’s pump, as without a stable base, it can vibrate freely, making quite a racket as it tries to escape from the main body of your hot tub spa! 


Speak to any manufacturer and they’ll recommend you drain and clean the thing at least once every 3-4 months. This is vital to eliminate the built-up body oils, sweat, bacteria and spent sanitisers that can lead to all manner of mucky gunks and slimes ruining your spa.

Most hot tubs drain from a single valve in the base of the shell, which works perfectly when it’s sat on a level base, but is utterly useless if the water all pools in one end! If you want to avoid scooping that water with a bucket, you’d better think about levelling your hot tub.

Long-Term Effects Of A Hot Tub Not Being Level

Failing to fix a sloped base for your hot tub spa can lead to plenty of avoidable problems, many of which will cause more pain than simply taking the time to resolve the issue; these include: 

  • Cracks, tears and fractures in your hot tub shell
  • Damage to your concrete pavers or slabs from uneven wear
  • Broken/noisy air jets operating out of the hot tub water
  • Difficulties in fully draining and cleaning the hot tub water
  • An increased risk of slips and falls when using the hot tub or spa tub

Last Word

There you have it! Our comprehensive guide covers how to level a hot tub on pretty much any sloped surface. Consider how much of a gradient your hot tub is currently sitting on, and decide whether a simple set of shims or an entirely new base will be necessary to help level a hot tub.

For hot tubs on sloped concrete, it’s best to lay a new base using self-levelling concrete, and if your hot tub sits on concrete slabs or pavers, you should try re-laying the surface.

There’s a method for any budget, and the results could save you a lot of time and money in the long run, so if you’ve got a wonky hot tub sitting in your garden, it’s time to get out there and fix it!

John Devlin

Hello, Welcome to my website. I’m John, and I created the InflatableHotTubGuide while researching these spas nearly a decade ago. Since its creation, the site has become the leading UK resource for many models. As a passionate hot tub user, I love to test and explore all the latest machines this industry keeps creating. I hope you find our content helpful.