Part 1: Building a Solid Hot Tub Deck Foundation

I recently bought a hot tub, which has been on my bucket list for many years. I've had it for about a month and on most days I use it at least twice - it's truly brought new meaning to the term "think tank" ;-)

This two-part Do-It-Yourself series will walk you through the deck foundation, and installing the deck boards.

Part 1: Building a Solid Hot Tub Deck Foundation.

Hot tubs are extremely heavy when loaded with water and people, and you'll need a solid platform to ensure the hot tub doesn't crack over time. I planned for a deck foundation that would support at least 100 PSI, and ended up with something that I probably could have parked a tank on... although you can never over-engineer when it comes to safety.

You can have a concrete slab poured if you can afford one, but in my case I wanted the beauty of a cedar deck.

First I cleared out the area and raked it so that it was level. This didn't need to be perfect, but I came pretty close with the help of a 4-ft long level I bought at Home Depot for about $20.

Then I bought concrete pavers to reinforce the deck joints, and several pieces of pressure treated 2x4 wood in 10-ft sections, and a few more in 12-ft sections for the outer edges. My total platform dimensions were 10ft by 12 ft, and I found it very helpful to lay out the pavers and boards to get an idea of spacing. 

I ended up making a few trips back to Home Depot to get the right number of pavers and boards, but hopefully this tutorial will help save you at least one of those trips :)

I used a 24-inch distance between the longer boards, and then cut center cross-beams at roughly 20 inches to go horizontal between the long boards... much like a ladder laying on the ground. I then screwed the individual "ladders" together to essentially form 4x4s.

This approach is far easier than trying to cut 4x4s, and the 2x4s can be screwed together to form a foundation that's nearly as strong as actual 4x4s.

I also bought a few bags of pea gravel to provide extra support under the beams, while facilitating good drainage during the rainy season. Pressure treated wood lasts a lot longer when it's not touching the ground and when it's kept as dry as possible.

Be sure you buy a contractor's square and take extra care to ensure that each section is as square as possible. This will help ensure the deck boards fit nicely on top of the foundation - which I'll cover in Part 2 of this series.

Total spend on the deck foundation was around $200 including the pavers, wood, gravel and deck srews. Your mileage may vary, depending on the size of your foundation.

Ready for the deck installation? --> Part 2 - Installing Cedar Deck Boards