How To Reinforce a Deck For a Hot Tub (In-Depth Guide)

This article provides a step-by-step guide on reinforcing a deck to make it stronger and more durable to support a hot tub using simple tools and materials.

A deck is one of the best places to install your hot tub. It provides the most scenic view of the surrounding areas and enhances the overall hot tub experience. However, it needs to be stronger and more durable to withstand the weight of the hot tub, including water and people. If you don't reinforce your deck, it can break under the massive weight of the hot tub.

There are many ways to build a deck, but most of them are costly and labor-intensive. Fortunately, there's a process of reinforcing a deck without spending much and can be done quickly with a few simple tools and materials.

How Heavy is a Hot Tub?

Hot tubs are incredibly heavy. A small hot tub can weigh 400 to 600 lbs. straight out of the showroom. Add water and people, and the weight is more than double. Here's how heavy a hot tub is with water and people to give you an idea.

how to reinforce a deck for a hot tub featured image

Small 2-3 person hot tub

  • Empty: 600 lbs
  • Water Only: 2,575 lbs
  • People & Water: 3,000 lbs

Medium 4-5 person hot tubs

  • Empty: 750 lbs
  • Water Only: 3,700 lbs
  • People & Water: 4,420 lbs

Large 6-8 person hot tubs

  • Empty: 800 lbs
  • Water Only: 4,300 lbs
  • People & Water: 5,500 lbs

Inflatable hot tubs (2-3 people)

  • Empty: n/a
  • Water Only: 2,200 lbs
  • People & Water: 2,700 lbs

Inflatable hot tubs (4-6 people)

  • Empty: n/a
  • Water Only: 2,700 lbs
  • People & Water: 3,700 lbs

As you can imagine, putting a hot tub this heavy on top of a deck will put tremendous stress on the wooden posts and joists supporting it. In other words, you can't put a hot tub on your deck without reinforcing it.

How Much Reinforcement Do You Need?

We know how heavy hot tubs are and that you should reinforce your deck to withstand its weight. But exactly how many joists and posts or how thick and wide they should be is something only a professional like a licensed engineer can tell.

As a rule of thumb, if your deck is not more than two feet above the ground, you don't need to reinforce it. To be safe, consult your local engineer so he can measure your deck's capacity and see if it's up to spec. This is critical, especially for two-story-high decks, because of the substantial risks involved.

Materials Needed

Here's what you need for a deck that's around 4 to 6 feet high. Reinforcing decks 1 to 2 stories high is more involved and is usually done by licensed contractors and engineers.

materials needed
  1. Wooden Joists - This depends on the size and number of joists that need reinforcing and the total weight of the hot tub with water and people. Some hot tub owners use 4x4 or 6x6 cross beams placed underneath the joists instead of adding extra thickness to the joists.
  2. Wooden Posts - For a small 2-3 person hot tub, four 4x4 or 6x6 wooden posts underneath the hot tub are commonly used as reinforcement. As the hot tub gets bigger and heavier, wooden posts are also spread much closer; hence, more posts are needed.
  3. Pre-cast Concrete Block Footings - You can buy these pre-cast concrete block footings from your local hardware store. Choose something that could fit your 4x4 or 6x6 post.

Key Takeaways: Have a local engineer inspect your deck before buying these materials so he can measure how much load it can take and give some specifications about the materials needed to reinforce it.

Reinforce Your Hot Tub Deck In 5 Easy Steps

  1. Fasten the reinforcing joist to increase its thickness or a 4x4 or 6x6 crossbeam under the joists to support it.
  2. Place the concrete block footing directly below the joist or crossbeam supporting the hot tub.
  3. Insert the wooden post into the concrete block footing and tap the posts with a hammer until it fits snugly perpendicular to the joist or crossbeam.
  4. Fasten the posts to the reinforced joist or crossbeam to keep it in place.
  5. Repeat the same for all posts.
reinforce your hot tub deck in 5 easy steps

Key Takeaways: DIY deck reinforcement saves you hundreds of dollars in material and labor costs. However, for decks one to two stories high, you need someone with training experience to do the work for you.


The deck's strength is determined by the material used to reinforce it. Always use high-quality lumber that can withstand enormous pressure from the hot tub's massive weight. Check with your local engineer regarding the strength of materials and how much of them are needed to reinforce your deck.