The following blog post was originally written and posted by Precision Pool Construction https://www.precisionpool.net/ and re-posted here with their permission. I found it to be very informative. I hope you do as well. One caveat, most modern residential decks in Georgia are built to support a 40 pound per square foot live load, not 100 pounds per square foot. If you plan to put your hot tub on an existing deck, we recommend consulting a structural engineer.
There aren’t many people who don’t dream of having a fun and relaxing hot tub in their backyard, but not everyone has the perfect place to install one. In this brief post, I want to go over what will, and will not work as a base for your new portable spa.
The Weight of Water:
Before we get into the materials we use for a hot tub base we need to first understand the characteristics of a portable spa filled with water. A hot tub dry just delivered to your house only ways a few hundred pounds and on its own could sit just about anywhere. The problem arises when you fill the vessel up with water, this makes a few hundred-pound tub a few thousand-pound tub…water is HEAVY!
The weight of the water is producing a lot of force onto that shell, thus the most important part of placing a tub is making sure it is 100% completely level. If the level of the spa is off the force of the water will cause the shell to stretch and warp over time, and this can cause serious damage to the unit. So how do we make sure our beautiful hot tub does not warp and crack? Use the proper materials and construction.
Placing a hot tub on a deck
Watch our new video: “Can I put a Hot Tub on a Deck?”
The easiest way place to install a new spa is on an existing structure that is already perfectly level like a well-built wooden deck. People often worry about the structural integrity of their deck and if it can support the tremendous weight a full hot tub. It is a valid concern but what we have found is that most any built to code deck are plenty strong enough to support a hot tub.
If you have a standard wood deck with 2”x8”’ joists 12” on-center with proper supports you are good to go. Even though the spa weighs up to 4,000lbs full when it is level the weight is evenly distributed over the bottom surface area of the tub at about 100lbs per square ft. This even weight distribution allows the deck to support the weight easily.
Existing Ground Level patios
A lot of times when we sell a hot tub the customer already has an existing ground level patio, made of concrete patio blocks. Just like a deck, this works great for the customer as no additional construction is needed. Unfortunately, a lot of these patios are pitched for drainage or have just buckled over the years and become un-level. If a slight pitch is found where the tubs is going you can get away with using some wooden shims to make sure the tub and water is level.
Paver Patio Installation
As we do a lot of paver patio installation we have recently been doing a few patio hot tub projects. Using a solid base material we install a complete concrete paver block patio using products from Techo-Bloc. Generally, this patio is much larger than just the hot tub base and we make sure the area where the spa is placed is perfectly level and then pitch the patio of rain runoff after the spa area.
Poured Concrete Spa Pad
When neither an existing deck or patio are useable for your new hot tub a lot of times the best option is a poured concrete pad. A concrete pad is great because you can get it to sit perfectly level and it creates a nice solid base for the spa.
We recommend pouring your concrete slab 3-4” thick using a 2”x6” wooden frame to create your form. If it is not a project you want to take on yourself here at Precision we can provide the pad installation for you.
Placing a Hot Tub on Crushed Stone
A simple and inexpensive way to prep the ground for a new spa is by using a crushed stone base. While not the prettiest or the most solid base it can work if done properly. The most important part of doing a crushed stone base to dig up the grass and topsoil and dig down about 3-4”. Try to level the ground a much as possible but it does not need to be perfect at this stage.
You then want to run a couple of 4”x4” stringers completely level across the area spaced about 4’ apart. This will give you something solid to set you level. You can now fill the area with 4” of crushed stone, make sure the area is about 4-6” bigger than the spa itself. Pack the stone down and level it as much as possible.
When you set the tub on the crushed stone the weight should allow it to settle into a level position with the 4×4 stringers helping.
A Prefabricated Spa Pad
Finally another available option is a pre-made plastic spa pad. These usually come in kits that you buy to fit your size spa.
The misconception is that these pads require no site prep which is completely false. You need to prep the space just like you would the crushed stone pad above. Dig up the topsoil and level it out before you put the pad down and place the spa.
It is very important to take your base into account when planning for a new hot tub at your home. The good news is we can help you every step of the way, even do a free at-home consultation to help find the best place to put it and what material will work best for your yard and budget.