Calculating if Your Deck Can Support the Weight of a Hot Tub

Your deck is where you host your family and friends to relax, entertain, or enjoy a meal surrounded by nature.

Maybe you want to take it to the next level and add a hot tub to your deck, but can your deck support a hot tub? What about if your deck is elevated?

Installing a hot tub on your deck can help maximize your investment. The closer the hot tub is to your house, the more useful it’ll typically be. You can relax after a long day or have friends over to catch up, all within walking distance of your home.

Can You Put A Hot Tub On A Deck

Yes, you can put a hot tub on your deck if it meets certain specifications and has enough support to ensure it doesn’t break through.

Decks on the ground level to two feet up can easily support around 100 pounds for every square foot, but any decks above two feet off the ground need additional support.

The support posts can be 30 inches apart and should be anchored in poured concrete to ensure they don’t move.

Before you take on this project, you need to know a lot more about decks and hot tubs because when they’re full of people and water, your hot tub’s weight easily exceeds 5,000 pounds.

We’ll go over how to calculate how much weight your deck can safely support, how to install a hot tub on your existing deck safely, and where to add additional supports to make the area below safe.

The Average Hot Tub Weight

Different kinds of hot tubs are available, and each hot tub will have a different weight when considered a standalone structure.

There are smaller two-person units, medium four—or five-person hot tubs, large six—to eight-person hot tubs and inflatable options. When empty, a hot tub weighs an average of 500 pounds.

It’s always best to double-check with your hot tub manufacturer about your model. Below is a rough estimate of how much your hot tub will weigh when it’s empty, full of water, and full of water with occupants. They include:

• Two or Three Person Hot Tubs – 600 pounds empty, 2,575 pounds with water, and 3,000 pounds with people and water.
• Four or Five-Person Hot Tubs weigh 750 pounds empty, 3,700 pounds with water, and 4,420 pounds with people and water.
• Six- to Eight-Person Hot Tubs: 800 pounds empty, 4,300 pounds with water, and 5,500 pounds with people and water.
• Two or Three Person Inflatable Hot Tubs – 2,200 pounds with water and 2,700 pounds with people and water.
• Four Six-Person Inflatable Hot Tubs – 2,700 pounds with water and 3,700 pounds with people and water.

How Much Weight a Deck Can Support

Generally speaking, the higher your deck is from the ground, the less weight it’ll be able to support for every square foot. In the following example, we’re going to assume you have a larger six to eight-person hot tub:

Get the weight of the empty hot tub

• 800 pounds

Find the number of gallons of water the hot tub holds and multiply it by how much a gallon weighs

• 525 gallons x 8.34 pounds = 4,278.50

Add your results from step two

• 800 pounds + 4,378.50 pounds = 5,178.50

Multiply the maximum number of people the hot tub holds by the average user weight of 175

• 8 people x 175 pounds = 1,400 pounds

Add your total to the previous total

• 5,178.60 pounds + 1,400 pounds = 6,578.80

Divide your total by the hot tub’s total number of square feet

• 6,578.80 pounds / 64 square feet = 102.79

So, according to your calculations, you can see that the biggest hot tub is over 100 pounds for every square foot if you have eight people in it at once.

This makes it impossible for your deck to support if it’s over two feet off the ground without additional support posts.

Figuring Out of Your Deck Can Support a Hot Tub

Although most hot tubs are relatively small, they can carry much weight concentrated in a very small area.

So, a deck more than two feet off the ground with support posts every six feet won’t be strong enough to hold your hot tub up when it’s full. However, there is good news.

If your deck is higher off the ground and easy to get under, it’s relatively easy to add more support posts and beams to distribute the weight more evenly and keep it stable.

If your deck is two feet or less above the ground, you won’t need to add additional support posts or beams. Still, contacting a professional contractor before you see what they recommend to keep your deck stable is a good idea.

That said, if you have a deck just off the ground, it can support around 100 pounds for every square foot. This is enough support for most medium-sized hot tubs that have both water and people in them.

Additional Factors to Consider

Since you could have a catastrophic deck failure if you don’t do your calculations correctly, you want to be 100% sure about adding a hot tub. Other factors will come into play, and we will highlight the most important ones below.

Material Age

Consider its age if you plan to install a hot tub and already have a deck. The wood on an older deck could be warped or weathered and need to be replaced because it is weaker.

The construction standards may not be up to par with today’s guidelines either if it’s an older structure, and everything from the main beam locations to the joist hangers and lag screws can impact how structurally sound your deck is.

Size

It’s hard to imagine what sounds better than walking out your doorway onto your deck from your bedroom and getting into a hot tub. But, if the hot tub completely takes over space because you have a smaller deck, this can lead to it feeling too cramped to enjoy.

Ensure you’re willing to lose space for your hot tub where you could put a table, couch, or other outdoor furniture.

Cost

A contractor could be happy to give you a plan to help you reinforce your deck to support the weight of your hot tub, but many people are surprised by just how much they have to pay to reinforce an existing deck.

Prices could start as low as $500 for minimal work and easily go up to $5,000 or more, depending on how many support posts you need and how you want them anchored into the ground.

Bottom Line

Now you know that you can put a hot tub on your deck if you’re mindful of the weight and whether or not your deck can safely support it.

You can calculate the weight and decide if you need to reinforce the deck before you add your hot tub. You can also plan out your project to allow you to create an oasis right outside of your door.