How to Determine if a Deck Can Support a Hot Tub?

How to Determine if a Deck Can Support a Hot Tub?

For those renovating their backyard, hot tubs can often play an important role.  But planning for your new addition is a very important job.  A hot tub filled with water and people will weigh several thousand pounds.  Without proper support, this can be a recipe for disaster.  If you are looking at how to determine if a deck can support a hot tub, our initial advice would be to seek the help of a professional.  This is not something that you want to get wrong – the results could be life-threatening.  However, there are some very basic calculations which can be made to determine the support necessary for a hot tub.  In this article, we’ll go over these calculations so you can make an estimate for yourself.

Concrete Pads

Hot tubs need to be placed on a flat, stable and level surface.  Concrete slabs are often used for this purpose.  Depending on the size of your hot tub, concrete pads that are 3.5 to 4 inches thick are usually installed.  Larger hot tubs may require a thicker concrete pad. 

Existing Decks

If you already have an existing deck, it’s very likely that it wasn’t built with the weight of a hot tub in mind.  Most decks are designed for people, patio furniture and a grill, not the thousands of pounds of weight found in a hot tub full of people.  If you already have an existing deck and want to install a hot tub on it, you will likely need to add support to allow it to bear the weight.

What Does A Hot Tub Weigh?

Of course, the weight of your hot tub will depend on the model, size and its construction materials.  But once filled with water and people it can easily weigh several thousand pounds.  As an example, if you have a six-person hot tub, the tub itself will likely weigh in the area of 1000 pounds.  The water needed to fill it would weigh just over 3500 pounds (420 gallons multiplied by 8.34 pounds per gallon equaling 3502.8 pounds.)  Add the weight of six large people and you’re looking at a total weight of around 5700 pounds.

Calculation of Load Bearing Requirements

Once you’ve figured out the total weight of a full hot tub, you’ll need to know its size.  To make this example easy, we’ll assume your hot tub is 57 square feet.  Divide the total weight of the hot tub by its square footage and you’ll come up with the load bearing weight per square foot required for your deck.  (5700 pounds divided by 57 square feet equals 100 pounds per square foot.)

What Next?

To determine whether your deck will be able to support a load of 100 pounds per square foot, you’ll need to consult a structural engineer or use some sort of beam-design chart, calculator or other software created for deck building.  You’ll also need some sketches of the existing deck frame to help understand where the main support beams run.  You’ll also want to take into account the load-bearing abilities of the soil in your region.  Unless you live on unusually swampy land, this is normally not a concern, but it still needs to be addressed.

Other Factors

When deciding on where to place the deck you should also keep in mind some other factors which could affect your enjoyment.  This includes the wind patterns in the area, proximity to leaf shedding trees and bushes, the amount of sunshine received, space for the hot tub cover and accessibility and privacy issues.

Now that you know how you can tell if you deck can support a hot tub. Download a hot tub buyer’s guide to learn more about our models.

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