How Bout a Cedar Ofuro Hot Tub?

Cedar Ofura Hot Tub

Hinoki is the traditional wood for ofuro tubs in Japan. Also named Japanese cypress, this slow growing tree is a rot resistant member of the Cupressaceae family. The timber chosen for ofuros is typically of the highest quality, tight, straight grain without knots. Hinoki wood, especially in North America, comes at a premium, which is big factor in the high cost of traditional ofuros. It is truly a luxury product worthy of the best craftspeople.

Cupressaceae Family

Cypress, Redwood, Cedar, Juniper, and Sequias are all native to the Pacific Northwest. Here in Eugene, Oregon, we are a major milling location for a range of rot-resistant woods, especially cedar. While we do have access to Alaskan cypress, often used in wood ship building, our abundance of both Western Red Cedar and Alaskan Yellow Cedar gives us access to a more local and extremely beautiful wood fit for soaking tubs.

Ofuro Tubs and Hot Tubs

I started out my journey mistaking an ofuro for a wood hot-tub. However there is a big difference between the two.

  • Ofuro tubs are typically small in footprint, relying on the natural buoyancy of being in water to provide relaxation.
  • An ofuro is similar to a bath tub in that it is meant to be filled and drained within a day at least.
  • Ofuros are typically meant for indoors, accompanied by permanent plumbing fixtures.
  • Hot tubs typically have complicated plumbing including air blowers and jets.

There is enough in common between ofuros and hot tubs to inspire a bridge between the two.

  • Ofuros are short but deeper than bathtubs, allowing water to the neckline as a hot tub does.
  • Both are therapeutic spas rather than for washing or cleaning.
  • Hot tubs, soaking tubs, and ofuros are meant to hold hot water and to be sanitary.

The dream for Elemental Works has been to combine the best of both for an ideal and simple hot soak experience. Take advantage of the beautiful, natural rot-resistance cedar, the simplicity of a small tub, the lack of permanent fixtures, with a neck-deep soaking experience.

From Plywood to Cedar

Building an orufo-style plywood tub with screws and resin was a no-leak success, so building a tub from thicker wood should be even better, in theory. However, in practice it is much more difficult.The basic requirements are to:

  • Build a box head-height while sitting with a fair amount of leg room.
  • That box should be able to hold water without leaking. Not just after a couple of hours or days, but continuously for months.
  • Sit outside year-round in sun, wind, rain, and freezing temperatures.

While my resin-sealed plywood tub performed well here, my first attempts at using 1″ cedar often did not last more than a few days to weeks. The combination of the cedar becoming saturated with water weakened its grain enough that it eventually deformed like wet cardboard to open just enough to allow the water pressure to create a leak. Water finds a way. And when reinforcing those leaks worked, the pressure along the sides of the rectangular tub caused cracking along the wood grain as the water tried to turn the box into a more round shape.

This was a good lesson in the power of plywood; Plywood is an engineered product containing many layers of wood grain in both horizontal and vertical directions, allowing it to bend without breaking.

Elemental Cedar Ofuro Hot Tub – Model 1

This was supposed to be it- the final product, just for me. I made full use of 1″ x 6″ x 6′ Western Red Cedar boards for a small ofuro-style tub of 24″ wide x 48″ long 30″ deep, external dimensions. The soak experience was better than the slightly larger plywood. It looked so much better, the water smelled of cedar oils, and I enjoyed the soft wood interior. It was a revelation.

The tub itself was very light, weighing less than 75 lbs, so I was able to move it around my patio fairly easily when empty.  It heated quickly from my tank-less water heater, recirculated from an accompanying pump.

One day after about two-weeks I came out to find the tub mostly empty. The wood softened, and un-reinforced, allowed just enough gap in a corner to let the water find its way to freedom, lower ground, and out of the tub.

Ofuros Are Not Hot Tubs

While we may love the beauty and elegant simplicity of wood ofuros, they are not typically designed to perform like we expect hot tubs to perform, at least in the U.S. Ofuros and similar soaking tubs are meant to be filled and drained within a fairly short amount of time, usually within a day. The water is either heated when filled, like a bath tub, or heated per use and let cool down again.

What I expect from a hot tub in this case is to always have the tub ready, with always-on hot water. For me, this isn’t about jets or bubbles vs relatively still soak, but a tub filled with neck-deep hot water at all times, available for a hot soak with minimal fuss whether I want to soak at 8am, 8pm, or if I wake up middle of the night and want to get in.

So with a couple of tubs of experience I was determined to figure out the long term solution I wanted. Meanwhile, friends caught on to my project, starting a long series of experimental tub recipes, refining all aspects on each iteration….


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