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Guide to Leveling a Hot Tub on Uneven Concrete Surfaces

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Are you looking for a way to level a hot tub on uneven concrete? No one wants to halfway drown on one end and sit high-and-dry on the other. Or worrying about water not fully covering jets on one side.

Leveling a hot tub on uneven concrete can be done with simple shims if the slope is less than one inch. For steeper slopes, leveling will require more involved solutions such as custom-built pads of wood, sand or gravel, or even a new concrete pad.

hot tub

We’ve written on how to level a hot tub on gravel, but if your hot tub is situated over an existing concrete surface, you may find that the concrete is somewhat unlevel. Whatever the case, you’ll want to read on for a few useful tips for leveling your hot tub over that uneven surface.

Use Plastic Shims

plastic shims

If your hot tub is out of level by an inch or less, consider using heavy-duty plastic shims to raise the low end. These shims are designed to be load-bearing, at close to 8,000 lbs, and are an economical way to level your slightly off-kilter hot tub.

Be sure to check your hot tub manufacturer’s guidelines on using shims safely. You definitely don’t want to crack the tub by shimming it incorrectly. Also, some manufacturers do not recommend shims at all; doing so may void the warranty on your tub.

Ideally, start with an empty tub (less weight to deal with) and begin tapping in shims on the lowest side. Place shims at regular intervals across the low side, so they provide even support for the tub’s full weight.

Each shim is close to 5/16 inch tall, so you may need to combine several together to get to the correct level height.

Use Wooden Shims and a Platform

For slopes more than an inch, you can build your own shims and a platform from pressure-treated lumber. After moving the tub aside, use pressure-treated 2×4 boards and a sheet of exterior grade plywood and:

  1. Cut the 2x4s into wedge-shaped pieces based on your specific slope.
  2. Insert them every foot or so across the low end of the tub base.
  3. Cut and attach exterior grade plywood to the wood shims with screws.
  4. Return the tub to its new, level platform.

Plastic Resin Base Pad

resin base pad

For added stability, consider topping your platform with a plastic resin base pad. Specifically designed for use with hot tubs, these pads are relatively inexpensive and have a lifetime guarantee.

They are made of heavy-duty plastic and can be picked up and moved if you ever need to relocate your hot tub. (For best results, your platform must be completely level.) These pads can also be used by themselves on any level surface.

Permeable Pavers

pavers

What the heck is permeable pavers? It’s a plastic grid that can be filled with sand, grass or gravel that can hold a ton of weight. To me it’s like a mix between the strength of a plastic hot tub pad and building your own pad. They are used for driveways but people have discovered their benefits for hot tub pads.

You place the pavers in a level area connecting how many you need and then fill them with a base material to make them permanent. They hold dirt’sand or gravel within the circles without fear of it washing away, so no edging is required.

The three main pros to using the pavers is that excess water will drain right through, they cost less than a hot tub pad, and they are easier to install than a custom built pad.

Purchase a Spa Leveler

A spa leveler can be used for a hot tub out of level by any measurement but is particularly appropriate when the uneven slope is greater than an inch, but less than 3 inches.

Several adjustable feet allow you to customize the spa leveler’s height based on the slope you’ve got to deal with.

If your hot tub is already in place, move it aside to put the spa leveler in the right place. You’ll need to know how far out of level your concrete pad is so that you can adjust the feet accordingly before reinstalling the hot tub on the new leveler.

While a spa leveler is a pricey option, typically costing between $600-$800+ not including shipping, it is constructed to last. The design allows water to drain away from underneath, so you don’t get wood rot or mildew under the tub.

An added benefit is its portability. If you ever need to move the hot tub, a spa leveler can be relocated and then releveled to the new spot’s location by simply adjusting the feet again.

Build a Raised Pad

What can you do if your hot tub is off by more than an inch and you don’t want to spend this year’s Christmas budget on a spa leveler or new concrete pad? Consider DIYing a leveler. A raised pad constructed from wood and filled with sand or gravel provides a stable surface for your hot tub.

A custom-built raised pad will require some carpentry knowledge and tools if you plan to do it yourself. If that thought makes you shudder, finding a local handyman who can do the work for you at a reasonable cost should be simple enough.

How to Make a Custom-Built Pad

Build a box frame out of lumber and fill it with small gravel to create a level area for your hot tub. For starters, you’ll need to calculate a few key things:

  • Slope measurement: how out of level is your existing concrete pad?
  • Amount of framing materials needed: 2×4 pressure-treated lumber and screws
  • Amount of sand or gravel needed to fill the frame

Build a Box

Using the 2×4 lumber, build a box frame that is approximately one inch wider than your hot tub base. Each piece of wood should be ripped and tapered on the bottom so that when the entire box is built and placed on the uneven surface, the top boards are level all the way around.

  • Pro Tip # 1: It’s critical that you use pressure-treated lumber to ensure that your new pad will stand up to the weather and any moisture around the hot tub.
  • Pro Tip # 2: Use joist tape along the top edges of the 2×4 lumber to keep water from sitting on top of the wood. If your wood is really wet, wait a few days before installing the joist tape.

Fill the Box with Gravel or Sand

Once you’ve built the box and fitted it to the sloping concrete, fill it with enough pea gravel or sand to come within an inch of the top; this gives you a sturdy base to put the hot tub on.

An alternative and optional filler for your custom-built frame box is cement. However, you should be sure that you’ll never want to move the hot tub before choosing this option since it’s a more permanent solution. This isn’t the best option if it’s already on top of a concrete slab.

Paint or Stain the Wood

If you want your new hot tub pad to have a more finished look, you can paint or stain it to match your tub base. It’s not a necessity but does add a professional, customized appearance.

One benefit to paint or stain is that the wood will have protection from the weather, on top of its already pressure-treated nature.  

Pour a New Concrete Pad

If all else fails and you’re just not satisfied with other leveling options, consider having a new concrete pad poured for your hot tub.

If your current concrete pad is heavily damaged, you may want to demo it and start fresh with new concrete. Just take into account the cost to demo your current pad along with the cost of a new one.

Or, it’s the perfect chance to relocate your hot tub to that spot in the yard where you really wanted to put it anyway. Either way, pouring concrete is expensive, but you may find it worthwhile in the long run. Contact a local concrete mixing plant to determine costs in your area.

Final Thoughts

Leveling a hot tub on uneven concrete is recommended to ensure the integrity of the tub itself and the users’ safety. There are several ways to accomplish this, depending on the tilt’s severity and your comfort level with DIY projects.

Whether you choose to shim it up, build a new pad, or purchase a prefab leveler, you’ll soon be enjoying a relaxing dip in your perfectly level hot tub.

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Jena Slocum Co-Founder

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