How to Determine if a Deck Can Support a Hot Tub

Deciding to buy a hot tub is an exciting moment for the new buyer. However, there are many considerations that need to take place before you’ll be able to enjoy the bubbling warmth of your new hot tub’s waters. Where you install your hot tub is one of the first things that you’ll need to figure out. Buying a hot tub is one thing, but figuring out exactly where to put it, and how, is quite another. You’ll have surely noticed that many hot tubs are built on decks. But the fact is that your average deck isn’t built to support a hot tub full of people and water. If you’re looking at how to determine if a deck can support a hot tub, this article is for you.

That said, it’s important to seek the help of an expert when it comes to installing a hot tub on a deck. If the calculations are off or done improperly, there’s a serious risk of damage, injury and possible death. Avoid a disaster and get professional help. At the same time, we believe it’s important to understand the basics when it comes to hot tub installation, so we’ve come up with an article to help you understand how to calculate the load bearing capacity necessary for an on-deck hot tub.

The Hot Tub Base

You will definitely need a flat, level and stable surface on which to place your hot tub. Concrete pads are typically used for this purpose. A four-inch-thick pad is usually enough to support your average hot tub. If you’re getting something that’s oversized or unusually heavy, you may need to pour a thicker pad. It’s best to consult with a professional if this is the case.

Your Existing Deck

The problem with most existing decks when it comes to hot tubs is that they haven’t been designed to bear the thousands of pounds that results from a tub full of people and water. Most decks are simply built to support some people and some patio furniture. The placement of the support beams beneath the deck will also play a role in where the hot tub can or cannot be installed.

Measurements Needed for Calculations

Calculating the load bearing support necessary for hot tub installation is actually quite easy. As long as you know the dry weight of the hot tub, the amount of water it holds, it’s square footage and the maximum occupancy, you can quickly calculate the force your deck will need to withstand.

Load Bearing Capacity Formula

The formula needed to determine the load-bearing capacity of your deck is the total weight of the full hot tub divided by its square footage. To arrive at the total weight of the hot tub, simply add its dry weight to the weight of the water and the weight of the people using the tub. As an example, we’ll say the hot tub itself weighs 1000 pounds, the water weighs 4500 pounds (a single gallon of water weighs 8.34 pounds,) and the occupants weigh in at 1200 pounds. With a total weight of 5700 pounds and a hot tub with an area of 57square feet, your deck will need to be able to withstand 100 pounds per square foot.

Assessing Your Deck’s Capacity

To determine whether or not your deck will be able to withstand 100 pounds per square foot will require the use of some engineering beam-design charts, engineering software or the expertise of a structural engineer. You’ll also need to have a sketch of the placement of your deck’s support beams to help determine its strong and weak spots.

Now that you know if a deck can handle the weight of a hot tub, download a free hot tub buyer’s guide to learn more about our models.