How to Build a One Person Hot Tub

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Furo is the Japanese word for a single-person hot tub.
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How to build the simple, practical and incredible Furo hot tub.
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Photo 1: Building a one-person hot tub.
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Photo 2: Building a one-person hot tub.
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Photo 3: Building a one-person hot tub.
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Photo 4: Building a one-person hot tub.
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Photo 5: Building a one-person hot tub.

This do-it-yourself project shows you how to build an affordable one person hot tub.

How to Build a DIY One Person Hot Tub

Back when Yuppies were “in,” a hot tub was the pinnacle of western civilization. It was letting go of inhibitions of the 60s, partying of the 70s and materialism of the 80s. Now though, we have the Karma of the 90s. Somehow (probably due to all that collected karma), group hot tub experiences have faded from popularity, but it still feels good to sit in hot water to soak away the stress and tension of the day.

Unfortunately, the standard Anglo-European household bathtub design is so obtuse that you have to be a contortionist to get any benefit. It was obviously designed for a parent to bathe a toddler, and no one else. Even if you can lie in it without your legs protruding, the large water-surface area causes the heat to evaporate within just a few minutes, thereby causing a cold tub, which is almost as effective as a cold shower for diminishing your interest in life in general.

Several years ago, however, I found a single-person hot tub invented in the Orient and now I am psychologically dependent upon it. It is small enough to be heated by a standard hot water tank, fits inside a standard bathtub, and is easily portable.

The discovery came through a chance visit to an inn in Cork, Ireland, which has made its fortune catering to Japanese tourists. In my bathroom was this amazing little bathtub. At first I thought it had to be a very deep utility sink, but being desperate, I tried it out. It was just barely large enough for me to sit upright with my legs crossed. But with the flotation of the water and the cocoon-like feeling, it was just right.

The brochure on the nightstand explained that it is called a furo. Furo is the Japanese word for a single-person hot tub.

The term “low tech” doesn’t begin to cover the simplicity and functionality of the design. No bubbles, no jets, no electricity, nothing to break, just deep hot water up to your neck. Asians have known for thousands of years the benefits of sitting alone immersed in hot water. And, as I have since learned, the favorite place for Japanese college students to study is in the furo.

Basically, it is just a plywood box with a cool Oriental name. At first glance it seems like you may have your knees in your mouth, but this is not the case, due to your natural buoyancy — you feel so good you just don’t care. I’m tall for a short person, over 5 foot10 inches, and I fit very comfortably. You get the same benefits of a hot tub, but none of the contamination consequences, plus you get to be alone and not feel completely antisocial. Try to remember, did you ever take a tub all alone and not feel self-conscious and wasteful? I did it once and felt as if I were driving a Winnebago to the grocery store.

By getting the temperature to as hot as you can stand, usually around 104 degrees Fahrenheit, your muscles relax so totally that you feel disconnected from your body. Your lymph system drains. Sweat glands open and all toxins dump like crazy. You will be clean as a whistle when you are done. And when you do get out, you will feel like human jelly for about half an hour. And you will be sweating. Put on a comfortable bathrobe and sit in an easy chair with a tall glass of water.

You can fill the furo with your shower, but it is more energy efficient to buy a $20 hand-held shower adapter so you can let the shower nozzle dangle in the bottom of the furo and fill it without letting the hot steam escape. It is best to get in it while it is filling, because you can stand the heat better if it is a gradual, rather than a sudden, entrance. To empty it, just pull the plug and the water goes into the tub and down the tub’s drain.

Adding a cup of Epsom salts to the bath can make for an even more pleasurable experience. For a total sinus opening adventure, add eucalyptus oil. To feel like King Tut, add flower petals.

One Person Hot Tub Assembly

  1. Buy wood and other supplies, and get the wood cut at the lumber yard.
  2. Take your two 26 inch by 28 inch sides and screw a 2 by 2 along the 26-inch sides; make sure the 2 by 2 is flush with the top of the panel. Insert the screws every 4 to 5 inches, at about 3/4, of an inch in from the edge. Don’t worry about an imperfect fit, the waterproof coating will fill the internal gaps later.
  3. Now take your two 20  inch by 26 inch side panels and screw them to the 2 by 2s mounted to the 26 inch by 28 inch side panels. The 20-inch sides should be the top and bottom, thereby making the width 20 inches. Just to double check, when you finish this step you should have a rectangular box that has the 2 by 2s mounted on the outside, with the internal dimensions somewhere near 20 inch by 24 inch. If it doesn’t fit, don’t worry, be happy, wood is very forgiving, just take it apart and start over. I did.
  4. Now make the bottom. Take the 20 inch by 24 inch panel and screw the two 20-inch 2 by 4 pieces to them along the 20-inch side, and then screw the 17-inch pieces along the remaining sides, so that the bottom looks like the one in the photo. Then insert the bottom into the box, with the 2 by 4s facing down, and screw through the plywood sides into the 2 by 4s to complete the basic structure.
  5. Now is the time to get some pretzels or chips to see you to the summit of this project.
  6. Mark and cut the hole for the drain. You can use a hole saw, jigsaw or ax (depending on your disposition at the moment). The drain assembly should fit perfectly, so tighten it down to about 800 ft/lbs to make sure it’s snug.
  7. Drill screw holes in the ends of the 1 by 2s and then assemble them along the top lip of the furo to make it comfortable to enter and exit, and to give it that finely crafted look of a turn of the century shipping crate.
  8. Now slather up the entire interior with either fiberglass resin, polyurethane, or marine-quality paint. To make it strong enough to withstand hurricane forces, you may wish to line the corners with fiberglass cloth and then slap on a final coat of fiberglass resin. Apply the chemicals outside, in a strong wind, while wearing a respirator to make sure that you do not breathe the fumes, which are very dangerous.

This little beauty is designed to fit inside your present mass-produced standard American bathtub. Make sure you get out when your fingers start to look like prunes. You may want to try a variation on the Scandinavian method by taking a cold shower between each hot soak.

Hot Tub Materials

  • One 4 foot by 8 foot sheet of 36 inch plywood, (4-ply if possible; you can buy a better grade of plywood if desired)
  • Cut into 2 pieces that are 20 inches by 26 inches for the front and back
  • And 2 pieces that are 28 inches by 26 inches for the sides
  • And a single 20 inch by 24 inch bottom piece
  • One 8 foot 2 by 4 cut into 2 pieces 20 inches long and 2 pieces 17 inches long, to support the bottom
  • One 8 foot 2 by 2 cut into 4 pieces that are 24 inches long to join the sides together
  • One 8 foot 1 by 2 cut into 2 pieces 28 inches long and 2 pieces 18 inches long to trim the top and protect your bottom when you climb into and out of the furo  
  • One tub-drain kit, with plug
  • One pound of 1 1/2 inch Sheetrock screws
  • One quart of fiberglass resin or polyurethane for the waterproof coating inside the faro 

Hot Tub Tools List 

  • Electric drill with Sheetrock screw bit 7/64
  • drill-bit for pilot holes in the 1 by 2s (otherwise they will split)
  • Jigsaw, or 2 1/2 inch hole saw, or ax depending on your attitude.
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