Can your deck handle the weight of a hot tub? We're here to shed some light. 

Decks and hot tubs make a fantastic duo. Still, it's important to remember that a high-end home spa can weigh as much as 100 lbs per square foot—that's double what a typical deck is designed to handle. So, before you start planning your hot tub deck project, examine your deck's structure to avoid any injuries or property damage. 

Let us explain how to determine whether your deck can handle a hot tub and how to prepare for deck installation.

Understanding Hot Tub Weight & Deck Load Capacity

Before introducing a luxurious hot tub to your deck, weigh a few key considerations. You need to be well-versed in the structural requirements for hot tubs and the specific load-bearing considerations related to their installation.

First, let's understand the weight of a hot tub and how it can significantly strain your deck's capacity. Here's how the hot tub weight sums up:

  • Dry or empty hot tub weight, which you'll need to get from your hot tub's manufacturer
  • The water's weight, considering that a gallon of water weighs approximately 8.34 lbs
  • Occupancy weight, averaging men's and women's weight at 200 lbs and 140 lbs, respectively

Calculating Pounds per Square Foot

Take a hypothetical hot tub that seats four people, holds 195 gallons of water, weighs 375 lbs empty, and occupies 29.17 ft². To find the pressure it would place on your deck, use the following formula:

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

After a simple calculation, you'll find that the hot tub would put around 93.97 lbs per square foot of pressure on your deck. 

Getting a professional hot tub deck evaluation before proceeding with any hot tub deck installation is crucial. An expert will assess your deck's weight capacity and determine whether any hot tub placement reinforcements are necessary.

Types of Hot Tubs & Their Requirements

Choosing a suitable hot tub model can also significantly influence your deck's structure and appearance. Hot tubs fall into two broad categories: recessed and on-deck.

  • On-deck hot tubs sit directly on a deck, so it's necessary to understand your deck's strength and determine whether it needs any modifications for this spa type.
  • Conversely, recessed hot tubs sit below the deck's surface, resting on a concrete slab or in a small hole you've excavated for them.

Remember, both of these hot tub types have unique hot tub deck framing and deck foundation requirements. Discuss these with your deck installer to ensure you meet all the necessary building codes. In both cases, the deck must have space for the access & control panel so that you or a technician can perform maintenance checks and repairs if necessary. 

Assessing Your Deck's Structural Integrity & Support

Installing a hot tub on an existing deck has become popular among homeowners striving for a luxurious spa retreat in their backyard or patio. However, the type, size, depth of foundations, joist size, general construction practices, and, more importantly, the deck's age are vital factors determining whether the deck can shoulder the hot tub's weight.

If you have a standard wood deck with 2x8 joists placed 12 inches in the center and constructed with proper supports, you shouldn't have much to worry about — even with a spa that weighs up to 4,000 lbs when full. Thanks to the hot tub's even weight distribution, when level, it can spread the weight over its base, exerting approximately 100 lbs per square foot.

Consider again the hypothetical hot tub that produces 93.97 pounds per square foot. This should be well within the load capacity of the well-constructed deck described above. However, while making rough estimates based on size and materials is feasible, not all decks are created equal. Considering the many variables influencing deck load-bearing capacity, booking a comprehensive professional deck evaluation is still the best route. The contractor or engineer will assess each deck component, from its foundation to its materials, construction, and age.

How to Prepare Your Deck for a Hot Tub

If you're determined to add a hot tub to your property's deck, here are some critical steps to take before you do so.

Reinforce the Deck

Deck modifications may become necessary if your deck lacks sufficient strength to bear the combined weight of your spa, the water, and the occupants. Reinforcement might involve:

  • Additional beams will be installed under the hot tub area.
  • Reinforcing the deck's joists.
  • Even replacing worn-out deck boards.

Consider Access 

When designing and reinforcing decks for hot tubs, the position of the deck is a vital factor. Easy access to the hot tub is essential and shouldn't obstruct walkways or common areas. Remember prevailing winds, trees, and other environmental aspects that can influence your comfort.

Keep Privacy in Mind

Open views and privacy are necessary for creating a relaxing environment. Remember local building codes for hot tub decks when you're planning any deck modifications around this, such as a fence or privacy screen.

Think About the Layout

Considering layout options early can save you from costly hot tub deck framing modifications. It also helps guide aesthetic choices like deck colors, materials, and lighting options that will make the space uniquely yours. Seek a professional deck evaluation or use design software to visualize your layout.

Ensure Proper Drainage

Hot tubs require a 4-inch (100 mm) concrete base to stabilize them, control drainage, and avoid pooling. If you install your hot tub on a slope, remove the soil where the pedestal support will go and pour a small concrete pad, about 30 x 30 cm, beneath each pedestal. Avoid placing the pedestal directly on grass or mud, which may sink under the hot tub's weight over time.

Determine the Plumbing & Electrical Setup

A nearby garden hose connection will be necessary to fill the hot tub. At the same time, electrical outlets will be essential for power needs. The demands of even the best luxury hot tubs can be pretty heavy-duty — think pumps, heaters, lights, and jets — so a proper energy setup is crucial and must comply with local safety codes. 

Hire a Professional Installer

Whether the installation is at ground level, above ground, or recessed into the deck, a professional installer can advise on the best strategies for hot tub placement on decks, assess your deck's strength, and ensure all the specifications adhere to the required building codes for hot tub decks.

Enhancements & Modifications for Your Deck

If your current deck isn't up to load capacity, you have two options: upgrade it to offer more support or scrap it and build a new one.

Upgrading Your Existing Deck

Your exact strategy may involve anything from installing extra joists to conducting extensive structural framing and foundation work, and the costs may vary. Consider having a professional assess your deck's weight capacity and evaluate its ability to support your chosen hot tub model.

Designing a New Deck

Planning the hot tub installation from the start could save you considerable hassle if you build a new deck. Work with your designer to create a deck that will directly support the weight of the home spa, negating the need for any reinforcements later. This might mean adding an extra beam under where you plan to place your hot tub. They will be able to walk you through different hot tub deck ideas and ensure you comply with all necessary building codes.

Frequently Asked Questions

How much weight can a deck safely hold?

To calculate your deck's support weight, multiply the total area by 50 psf (pounds per square foot). For instance, a 100 sq. ft. deck should safely support 5,000 pounds. Please note, however, that this is only an estimate.

What should be placed under a hot tub on a wood deck?

If your deck is close to the ground, consider placing your hot tub on a concrete slab near the deck's edge. This provides a stable base, and you can then build deck tiers around the hot tub for easy access.

Can a deck support a spa?

Yes. Spas can be safely installed on top of or built into decks. However, the deck's structure must be confirmed to support the weight and comply with local council rules and regulations.

How do you reinforce a deck for a hot tub?

Reinforcement involves adding additional joists and beams to your deck. Consult a professional builder or structural engineer to ensure your deck supports your hot tub model.

April 09, 2024 — andrei newman