Hot Tubs in Garages: What Could Go Wrong?

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One of my neighbors recently put an inflatable hot tub in his garage.

I’ll admit, that’s something I would never have thought of.

Most people don’t have an extra room inside their home or enough deck or yard space to set up a hot tub outside. Plus, there’s a lack of privacy unless you have a lot of land.

However, before setting up the hot tub in the garage, there are some things that you need to know. 

Putting a Hot Tub in Your Garage: What Could Go Wrong?

Whether you add a temporary inflatable hot tub or go all-in and permanently install one, there are some things to consider first.

Here are some ways that putting an indoor hot tub in your garage could lead to big repair bills down the road.

Not Having Enough Ventilation

Putting a steaming hot tub inside your garage adds a lot of additional moisture and humidity to the air. 

Over time, that will damage your garage walls, tools, electronics, and everything else stored inside unless you upgrade your garage ventilation system.

Additionally, the EPA recommends keeping the relative humidity indoors between 30% and 50% to prevent mold growth. 

How much ventilation you need will depend on what area of the country you’re in and the base humidity level. 

For example, here in Florida, I struggle with keeping the humidity level in my garage under 60%, even without the additional moisture of a hot tub. 

In contrast, someone in arid Arizona could easily get by with less. 

At a minimum, plan to install an exhaust fan, dehumidifier, and fans in your garage. That will help prevent damage to your garage interior and avoid potential health risks from mold and mildew. 

Not Having Water and Slip-Resistant Flooring 

Poor ventilation may cause damage to your garage down the road, but a slippery epoxy garage floor can ruin your day pretty quickly. 

Slips and falls are common hot tub accidents, even on an outdoor wooden deck. Inside your garage, a slip-resistant floor is a must.

Most garages have bare concrete or epoxy floors, which can get slippery when wet. If you’re putting a hot tub in your garage, you may need to modify it to make it slip-resistant. 

This may be as simple as adding a non-slip mat around your hot tub. Alternatively, you can re-coat your garage floor to make it less slippery. 

Concrete sealants, rubber, interlocking garage floor tiles, or an epoxy coating are all excellent options. That will help keep you safe while protecting your garage floor as well. 

Mold & Mildew Growth on Insulation

We covered the importance of controlling humidity levels in an earlier section. Still, it becomes even more critical if you have an insulated, non-air-conditioned garage.

Let me explain.

Even with an adequate ventilation system, you can still suffer moisture damage due to excess humidity.

Mineral wool and fiberglass insulation work by slowing airflow and trapping it.

Unfortunately, when there’s a high concentration of moisture in the air, it can lead to mold and mildew growth.

Although this can occur in any garage, the problem is exacerbated in insulated but non-conditioned garages.

Wooden surfaces are also susceptible to mold and mildew growth. Be sure to protect the doors and other similar surfaces.

There are some steps you can take, including different types of insulation, which can help create a moisture barrier on the walls.

For example, you can install waterproof drywall and coat it with moisture-resistant paint.

Not Thinking About Plumbing First

If you’re putting a permanent hot tub in your garage, you’ll need to figure out the plumbing. Even if you have your water heater in your garage, there probably isn’t an easy way to get water to your hot tub. 

Filling up your hot tub with a garden hose can be exhausting. Before bringing in the hot tub, consider installing a water source in the garage to make it easier down the road.

Luckily, most hot tubs have self-contained plumbing systems. So once you connect the water from the line to the tub, you’re ready to go.

Most people forget about a drainage system, however. You’ll need to drain your hot tub every so often, at least for cleaning. Having a drainage system ready will make that process much more convenient. 

Similarly, you should level the flooring to allow water spills to drain away quickly. Here’s where a garage floor drain would be beneficial.

Standing water increases the risk of slips and falls and can be a breeding ground for mosquitoes in your garage. 

Choosing the Wrong Hot Tub Size

There’s always a temptation to buy as big a hot tub as possible so you can accommodate all your friends.

Go big or go home, right?

While that sounds like a great plan, you want to keep the space manageable so there’s room in the hot tub area to move around.

Dealers provide recommendations for the appropriate tub for every garage size. So ensure you install one that fits your space.

You are required to leave at least an extra foot around the hot tub to give room for maintenance. There should also be space for installing hot tub steps and a towel rail.

Naturally, you can customize the space however you want, adding extra amenities. But consider all the options you need before selecting the hot tub. 

What to do Before Installing an Indoor Hot Tub in a Garage

Once you have handled the basics, the next step is buying and installing the hot tub.

Before you do, here are some tips to make your indoor hot tub installation go smoothly.

Measure Your Space

Unless your garage is packed full of boxes, every garage should have enough space for a standard hot tub. 

However, you’re not going to be using all of that space for a hot tub, even if you have an empty garage. 

Before buying your hot tub, measure the area you’d like to use so the dealer can recommend the ideal tub based on your garage size.

I also find it helpful to tape off the size of the hot tub on the floor, so you can “live with it” for a few days or weeks. I’ve done that with garage cabinets and office furniture, and it’s helped me avoid buying the wrong-size items. 

Installation Day

Once you choose your spa/hot tub and have it delivered to your home, all you need to do is set it up inside the garage.

Getting the hot tub in your garage shouldn’t be a problem. Garage doors are between eight and sixteen feet wide, so there’s plenty of space.

The problem occurs when homeowners don’t clear enough space for the installers to work.

You’ll also want to make sure they have easy access to all the basics, like floor drainage and water supply.

Once the hot tub is delivered, you’ll probably need to hire an electrician to connect the electricity.

When working with electricity, I always recommend hiring a professional to connect and test the power to ensure it meets the correct voltage. You may need to add a high-power line and circuit breaker.

That’s usually beyond the capabilities of the average DIY homeowner. 

Post Installation Tips

In the days and weeks after installation, pay special attention to anything that seems ‘off’ in your garage.

Monitor the humidity levels and electricity usage closely and test anything you had to install (ventilation, plumbing, etc.).

For instance, you can use a hygrometer to test the humidity levels and visually check for signs of mold and mildew on surfaces regularly.

Similarly, check whether the drainage is working correctly and react accordingly.

You want to handle any potential problems before you have three hundred gallons of water pooling on your garage floor.

Always Cover the Hot Tub

 Just like you should use a car cover inside your garage, you want to protect your hot tub from dust and debris inside your garage.

Open hot tubs are potential safety hazards, especially if you have small children or pets. 

Curiosity might nudge them to sneak into the garage and take a plunge, exposing themselves to the risk of drowning.

Even if you don’t have young ones or pets to worry about, always use a hot tub cover. It helps reduce the humidity and moisture levels so you aren’t storing things in a damp garage. Plus, it helps keep your family safe.

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Tim Wells

Tim Wells, the founder of Garage Transformed, has been featured in dozens of home renovation publications, including, Home Stratosphere, House Digest, Livingetc, and SFGate. Since 2018, he has helped over two million people transform their everyday garages into something they can be proud of. He lives in Central Florida with his wife and bulldog.