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How to Determine If a Deck Can Support a Hot Tub

Can a Deck Support a Hot Tub? How Do I Install One?

Amore Bay Luxurious Hot Tubs

If you are adding a hot tub to your backyard, then the deck is the logical place to put one. Will your deck hold the weight of your hot tub?

A hot tub is an exciting addition to any backyard and may be a viable option for those who live in colder climes or have limited space. So how do you determine if your existing deck will support a hot tub? Here we’ll take a look at some factors that should be considered before installing a hot tub on a deck. 

Let's start with the most important question: how much weight can your deck support?

How to Calculate Your Hot Tub Weight and Deck Load Capacity

The short answer to the question, "Can my deck hold my hot tub?" is to add up the weight of your hot tub, including all the things that go with it.

Here's the list:

  • Weight of the empty hot tub - You'll need to consult your hot tub's manufacturer for this figure.
  • Total weight of the water in the tub - A gallon of water weighs about 8.34 lbs. You will need to account for the total amount of water in your tub.
  • Allowance for the people in the tub - Men weigh about 200 pounds on average, while the average weight of a woman is 140 lbs.

The next figure you need to know is the square footage of the base of the hot tub. You can use the figure to work out the amount of pressure your tub will put on each square foot of the deck it rests on.

Here is the final formula:

[Weight of Hot Tub + (Number of Gallons of Water x 8.34 lbs) + (Number of People Spa Can Seat x 185 lbs)] / # of Square Feet = Pounds Per Square Foot

As an example, a hot tub seating four people and holding 195 gallons of water, with an empty tub weight of 375 lbs and a footprint of 29.17 ft2, would produce 93.97 pounds per square foot.

Can Your Deck Support Your Hot Tub?

There is not a simple answer to this question. People throw out numbers like "decks can support 100 lbs per square foot." Simply put, the only way to know how much your deck will hold is to ask a qualified contractor to calculate this for you.

However, building codes usually specify at least 50 lbs per square foot for the weight the deck can support. 

In addition to the weight the deck can support, the type of hot tub you choose makes a difference to the deck support it will need.

Types Of Hot Tubs for Decks

The type of hot tub you choose determines where the weight of the tub will be placed. There are, generally speaking, two kinds of hot tubs. Choose the one that suits your budget and deck placement.

In-Ground Hot Tubs

These hot tubs usually sit below the surface of your deck and rest on a concrete slab, the ground, or in a small hole excavated for the purpose. They require much less support than an above-ground hot tub.

Above-Ground Hot Tubs

An above-ground hot tub sits directly on the deck. All the weight of the tub rests on the deck surface and supports. These may require additional supports to be added to the bottom of the deck.

There are just a few more things to consider when you are deciding about putting a hot tub on your deck.

A Few More Things to Consider To Put Your Hot Tub on Deck

We've got a shortlist of the extra factors you can think about while you're making plans for putting your hot tub on the back deck. Have a look and think about how your deck and tub will work together to create the perfect backyard space for you and your family.

Weight of the Hot Tub

We've already mentioned this, but it's pretty important. To make it simple, we recommend having an approved contractor inspect your deck. They can advise you of the amount of weight your deck can safely support.

Decking Materials for a New Deck

The material you choose for your deck will determine how much weight it can hold as well as a few other aesthetic matters. You have a few options:

  • Composite decking materials can mimic beautifully the look and feel of real wood. They are also rot and fungus resistant, so they may last longer than an organic wood.
  • Pine, especially pressure-treated wood, may be the least expensive choice for your deck. Pressure treated wood may be prone to warping and discoloration.
  • Cedar, like Western Red Cedar, is a fantastic alternative for decks with hot tubs. It stands up to moisture, insects, and fungi. It is also soft underfoot, which reduces the likelihood of splinters.

Decks can be made of other materials as well, such as concrete or tiles. These may be beautiful surfaces, and you'll need a contractor to look at them with you to determine the best installation.

Age of the Materials in an Existing Deck

Adding a hot tub to an existing deck is certainly a possibility. However, it is even more important to have your existing structure looked at by a professional. The boards and supports may have deteriorated over time and be unsuitable for use. This is especially true if you are evaluating an elevated deck frame.

An existing deck does not necessarily need to be replaced. It may be possible to replace the deck boards and add extra beams for support. This would help your wooden deck support the thousands of pounds of weight of your hot tub.

Access to Deck

Access to your deck comes via a door or steps, or both. You should position your hot tub close to your home to make it easy to get in and out. This will help you get the most out of your hot tub.

If you have steps leading to your deck, then consider whether you want to position your hot tub close to the steps. Nosy neighbors, noisy pets, and wandering children could all disturb the peace of your home spa. Think about your deck layout and where you want to place your hot tub for the best results.

Size of the Deck and Other Furniture

Your hot tub may fit on your deck, but is it too big? You'll need space around your hot tub to get in and out. Outdoor furniture, a BBQ, and the hot tub pump maintenance equipment may all need room. If you have an existing deck, it may be worth marking out the area of your proposed hot tub. Then you can visualize how all your plans will come together.

Water Source for Your Hot Tub

Hot tubs are generally closed systems, which means they don't lose that much water. However, some water can be splashed out during use and other water may evaporate. So, you'll need a water source to add water back to your hot tub on occasion. Place your hot tub somewhere close to your water pipe.

You're Going to Need Power

Your hot tub's pump, heater, lights, and hot tub filter will all require power. To supply this, install a proper power supply, including weatherproof wiring and an adequate power source. An electrician can help you choose and install the best equipment for your setup.

Make Sure You Can Easily Get to the Access Panel for Servicing

Routine hot tub maintenance, such as changing the filters and servicing the pump, means you will need to access the equipment. If you're placing the hot tub near your home or an existing fence, then ensure all access panels can be easily reached.

Cost of Reinforcing the Current Deck

If the load-bearing capacity of your deck is not high enough, then you will need to add additional support beams. This could be costly, especially if your deck is more than a few feet above ground level. Constructing an adequate deck that meets the building code and supports the heavy load of your tub could cost hundreds of dollars.

Lower decks could be made sturdy enough with concrete footings, new decking boards, and extra supports. This could be less costly and faster to complete.

Designing a Deck to Hold a Hot Tub

If you are building a new deck, then it can be designed for the weight of the hot tub installation. This usually means adding an additional beam or two under the area where the hot tub will sit. There is no need to overbuild the entire deck. Instead, you can just add extra support to the hot tub site.

A qualified professional can help you design a deck that will support the hot tub you want. So, whatever your hot tub deck ideas, you can almost certainly build a deck to suit it.

Conclusion

Now you know the final answer: Add up all the stuff with your hot tub and then work out if it is too much for your deck. If it is, then make a plan for how to reinforce your deck or build a new one.

FAQ

Can My Deck Support A Four Person Hot Tub?

Most decks built to code are only rated to support 50 lbs per square foot. This may not be enough to support your hot tub, especially if you have a second-floor deck. Additional support may be required.

How can I modify my deck to hold a hot tub?

Yes, you can add concrete deck footings, more supports, and other features to increase its weight capacity. These happen underneath your deck. If necessary, you may have to cut and reinforce a hole for the hot tub if you want it to sit below the deck.

Can I put an inflatable hot tub on my deck?

Yes, probably. You still need to calculate the weight of the hot tub and whether the deck can support its weight. The formula we supplied above for calculating the total weight and pressure per square foot is applicable here as well: [Weight of Hot Tub + (Number of Gallons of Water x 8.34 lbs) + (Number of People Spa Can Seat x 185 lbs)] / # of Square Feet = Pounds Per Square Foot. Anything above 50 lbs per square foot may require additional strengthening.

Custom Backyard Spaces is Here to Answer Your Hot Tub and Decking Questions

If you’re thinking about buying a hot tub for your deck, the team at Custom Backyard Spaces is here to help. Contact us today at  919-444-8500 or fill out this form to learn more.