Project Breakdown: How to Build a DIY Wood Fired Hot Tub for $2300

Where do you live and what do you do for a living?

Theresa and I live in Priest River, Idaho. I'm a graphic designer and photographer, and Theresa is a stay-at-home mom (for now) and also a creative genius.

Where'd the idea for a DIY wood fired hot tub come from?

Theresa and I grabbed a cheap 2’x4’ galvanized stock tank at a yard sale a few years back and installed it on the edge of the yard near the forest. It quickly became an integral part of our Idaho summers. When the temperatures hit 90°, a quick dip in the cold tank could turn a sweltering slog of a day into a real delight. We’d grab a couple cold Rainiers and a towel, chill ourselves to the bone in the 50-degree fresh water from the well, then pop out and soak up the sun until that cold water sounded nice again. But summers here are short, and soon our thoughts turned to a cold-weather version of the same experience.

What inspired your design? Can you share any reference projects, books, or IG accounts?

We've been talking about a wood-burning hot tub for years, and had been looking at Goodland tubs, which are very cool, but we just couldn't afford the $5,795 base price. Knowing we had access to a woodworking shop and tools that belonged to my late father-in-law, we figured we could make something just as cool for half or a third of the price if we were willing to put in the time and effort

Some friends in Sandpoint, ID (shout out Tanner Welch and Tess Howell) were super helpful early on. They'd created a similar setup a few years back with a four-foot round tub and the exact same Chofu stove as the hot tub’s external heater that I've had my eye on for a while. They let us come by their place to check it out and shared a few tips and tricks for proper setup. We took that basic concept and adapted it to a 2'x6' tub.

Jesse Lenz has a double stove setup for his huge open air tub and also shared some great advice on how to get the heat dialed in.

Also, I've wanted to try the Japanese Shou Sugi Ban traditional wood charring method ever since watching The Birth of a Wooden House and we figured this would be an ideal project for it since it's supposed to be a highly durable, long-lasting treatment for exterior wood. Another source of inspiration was the Soot House episode of Home on Apple TV, which features a home in Maine built by Anthony Esteves and Julie O'Rourke.

Did you have construction or DIY experience going into the project?

In college I had a summer job for several years with a home remodel construction company doing grunt work and basic building work alongside one of the company's primary carpenters. I learned a lot, but was still very much in the entry-level phase in terms of building knowledge. For a job like this some basic building knowledge will be required—I'd classify it as solidly intermediate level.

It'd be a simple project for anyone who builds for a living, but if you've never built anything you might want to call your pal who knows what he's doing. You'll need to know how to level and square a deck, and have some familiarity with basic tools like a chop saw, table saw, drill, jigsaw, etc. That said, if you're comfortable with that kind of stuff it's not rocket science. Think everything through carefully, read the instructions for the tub hookup, measure twice, cut once, and you'll be alright.

What wood stove did you use, why, and how is it performing so far?

We used the Chofu stove from Islandhottub.com. This stove is incredible, high quality, very efficient, and weatherproof. I'd estimate it takes two hours heating time, and four to five pieces of cord wood (split into 2"x2" pieces) in the firebox to heat our 175 gallon tub from cold (50° well water) to 102°.

The Japanese-made Chofu stove.

Cost Breakdown & Time Commitment

Total cost: $2,200-2,300*
- Chofu Stove, $1200 + tax & shipping
- 2'x6' galvanized stock tank, $300
- All deck materials, $700-$800

Total time: Approximately 60 hours (30 hours x 2 people)**

*This would probably be closer to $3,000 without the cost savings from using salvaged siding, and free screws and nails, and could be dramatically more expensive depending on what materials you use. For example, 2x6 fir for our deck was $10/board for an 8' piece. Cedar in the same size & length was $50/board (which is why we used fir).

**This could be significantly less for an experienced builder who doesn't have a four-year-old and seven-month-old to take care of at the same time. Everything seemed to take me twice as long as it should.

Lessons Learned

1. Get in the tub before you buy it!

We got a 4' round tub first after seeing Tanner and Tess’s setup. But I'm 6'2" so when we got it home and I sat down in it we immediately realized it was too short for my long-ass legs and I had to drive it back to the hardware store to swap out for the 2'x6' tank. We think the 2'x6' is the perfect size for two people. We also considered a 3’x8’ tub to accommodate four people, but that was a jump from 175 gallons (two hours to heat) to 300 gallons (four-plus hours to heat), so we stuck with the two-person tub.

2. A cold plunge tank is a must.

We have a 2'x4' galvanized soaking tub off to the side of the deck which we fill with cold well water from the hose. After 5-10 minutes in the hot tub you start to get overheated. A quick dip in the cold tank is invigorating, stimulating, and makes the hot tub feel even nicer when you get back in. After three or four hot/cold exchanges you become extremely relaxed.

3. Call Frazer.

If you get a Chofu, call Frazer at Islandhottub.com directly to place your order, and ask any questions. Expect a 30-day wait time as wood fired hot tubs are growing in popularity post-COVID. Frazer is the sole US importer of Chofu stoves (via Japan) and is incredibly knowledgeable and happy to walk you through everything in detail. The kit he provides comes with all the hardware and instructions you need to get the stove hooked up to the tub.

4. Hand pick your lumber.

Any lumber yard worth its salt will let you hand-pick your boards. Home Depot is fine too, but a proper lumber yard typically has nicer wood. Look for warped, bent, or chipped boards and set them aside. Pick the cleanest, straightest stuff you can find and it'll make your job a lot easier.

5. IMPORTANT: Check your minimum water level.

Before you hook up your Chofu wood-burning stove (or similar stove), fill your tub and get in the water with the maximum number of people you intend to use it at any given time. Then get out, and make note of the water level. Make sure to install your hot tub water inlet BELOW this level.

This step is crucial because of basic displacement principles. Bathers displace water, raising the water level of the tub. This also means that when those bodies exit the tub, the water level drops again. You need to make sure that your minimum water level remains ABOVE your hot water inlet at all times. If the water drops below the minimum level, hot water in your stove coil has nowhere to go and turns into super hot steam, which can rupture the coil and ruin your expensive stove.