How Thick Should A Concrete Slab Be To Hold A Hot Tub?

How thick should a concrete slab be to hold a hot tub? Who doesn’t want a hot tub right in their backyard? No matter what time of year, a hot tub can offer a nice, …

How Thick Should A Concrete Slab Be To Hold A Hot Tub

How thick should a concrete slab be to hold a hot tub? Who doesn’t want a hot tub right in their backyard? No matter what time of year, a hot tub can offer a nice, relaxing soak to take away the stresses of the day.

Not only that, but there are a plethora of health benefits that can be felt by having a hot tub. But it is not as simple as buying a hot tub and sticking it in the backyard.

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You need to have a base for your hot tub and picking the right one is crucial. Here is all that you need to know about having a base for your hot tub: what works, how to acquire one, and what not to use.

How Thick Should a Concrete Slab Be to Hold a Hot Tub?

The optimal concrete slab should be around four inches in thickness. It also has to be rated to withstand about 115 pounds for every square foot. This might sound kind of obvious but a hot tub, let alone one that is full of water, is quite heavy.

That is why it is so important to have a strong base beneath it. Moreover, the base should be level to prevent structural damage within the hot tub over time.

The reason that concrete is the most common choice is that it makes for a great foundational base for just about anything. When laid, that concrete slab can also be made completely level to ensure optimal installation.

The one caveat of concrete is that it can be quite expensive. The good news is that you won’t have to provide much in the way of maintenance. Further, having a hot tub on a concrete slab can provide additional value to your home.

But it is imperative to choose the right slab thickness first. When you have a larger hot tub, this becomes especially important. It is also of the utmost importance that the concrete be fully cured before supporting any weight.

If concrete does not have the proper time to cure, it can lose structural support and crack. If the foundation cracks in any meaningful way, it may not be able to support the weight of the hot tub for very long.

Do I Need a Concrete Slab for a Hot Tub?

The short answer is “no.” A hot tub needs a base for sure, but that base can be one of a number of other materials instead of a concrete slab.

Hot tubs can be placed on paver stones, wooden decks, gravel beds, or simply spa pads. Whatever you do, do not place the hot tub on the ground directly.

If you have a wooden deck, make sure that it has been built to properly support the weight of that hot tub. There’s nothing worse than having a hot tub and a wooden deck ruined.

The most optimal choice, however, is a concrete slab. It can be made completely level and is more than strong enough to stand up to the weight of the hot tub.

How Long Should Concrete Cure Before Putting Weight on it?

Remember, a part of getting a solid foundation is to allow the concrete to cure properly before putting any weight on it. Concrete cures through a chemical reaction between the cement and the water that gets added in.

The reaction between the two is what ultimately binds the gravel and the sand together to form concrete. Fully cured concrete will be structurally sound and should stand up to cracking and other structural damage for a long time.

Concrete that has been freshly poured can take up to 28 days to fully cure. Over this process, which is also known as hydration, the slab requires moisture to remain in the concrete.

If that moisture dissipates, then the concrete will be much weaker at the finish. You may even notice stresses and even cracking throughout.

Over the first few days after pouring the concrete, it is imperative to control the temperature and moisture content of the concrete. You can’t simply pour the concrete and forget it or you may wind up with a structurally compromised slab at the end.

You can improve the structural integrity of the concrete, making it more resistant to cracking, by paying attention to it in those days after the pouring.

Moist curing was one of the more common methods of curing concrete in the early days. That means spraying it down with water frequently to ensure that it stays hydrated.

Hose the concrete down anywhere from 5 to 10 times every day for that first week. The moisture within the concrete will evaporate slowly but concrete that has been cured this way winds up being up to 50% stronger than concrete that has not been cured this way.

If you are pouring concrete during a cold weather period, do not spray. If you can’t do the moist curing, use a cover that will trap the moisture in and slow down the evaporation process.

Polyethylene sheeting, at least 4 mm in thickness, or a concrete curing insulating blanket should both work fine. All you have to do is wet down the concrete thoroughly and then cover it.

Can You Put a Hot Tub on Cinder Blocks?

If you don’t want to shell out for a concrete slab, there is an alternative. Cinder blocks, also known as pavers, can also be used in place of the concrete slab.

The good news is that there are more than a few different types of blocks that you can choose from: cobblestone, brick, concrete, rubber, and flagstone.

That said, there are a few things to be aware of before choosing this method. For one, raised pavers, particularly those with ridges or bumps, can ultimately put stress on the shell of the hot tub.

If you do go for pavers, make sure that they are smooth and that they interlock to create a completely flat surface. Cinder blocks, however, are a very dense material.

They offer more support than wood and even some concrete slabs depending on how flat and even they are. They have a low absorption rate that makes them resistant to some of the common issues that face poured concrete, such as efflorescence.

That is where salt deposits can rise to the concrete’s surface. If that weren’t enough, cinder blocks offer easier access to the underside of the hot tub in the event of issues with plumbing lines or buried electrical.

Just remove them to get to the problem and put them back when you are done. Cinder blocks also offer a wider array of design choices. They come in a ton of shapes, colors, sizes, and textures.

Lastly, you don’t have to wait a month for curing if you have cinder blocks. You can literally go to your home improvement store and have a pad built all in one afternoon.

Can a Hot Tub Sit on Decking?

The short answer is “yes,” with a “but.” It is very common to see hot tubs sitting on wooden decking. That said, there are things to be aware of.

The last thing that anyone wants is to have a hot tub not rated to support a hot tub, leading to damage for both. If you put your hot tub on a wooden deck, know the weight of the hot tub as well as the weight that the deck can support.

You may not have a situation where the hot tub falls straight through right away, but a weight imbalance can weaken the structural support of the deck over time.

Surface-level decks can, in most cases, take on the full weight of a hot tub that is fully-loaded. The further from the ground the deck gets, the more likely the need will be to support it.

There are plenty of ways to estimate how much weight your deck can support and how to reinforce the deck posts should that be needed.

Also, make sure that you have plenty of space around the hot tub so that you can remove the cover. It will be a huge pain if you can’t access the lid to remove it. Not only that, it ensures that you or guests can get in and out of the hot tub with no problem.

Finally, make sure your deck is sanded. There’s nothing worse than stepping out of your hot tub only to be greeted by a splinter!

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