Japanese Ofuro Soaking Tub

[Rob Sack]

I am interested in building a Japanese soaking tub, but am having difficulty finding any information of what type of joinery would produce water tight joints, especially in joining the bottom to the sides. Any suggestions or sources?

[Sam Murdoch]

Let me know I was getting ready to post a similar question for a 2 person cedar hot tub. Anyone out there (in here) have experience with such a project?

[john lampros]

Rob, I'm in the same boat (tub) you are. been contemplating the same thing. unfortunately I'm no help. what little I've found might be of some help though. It seems the traditional Japanese tub was built like a coopered bucket or barrel in that it isnt watertight till it has had water in it and should not be left to dry (emptied). In that traditional home it was no big deal if it leaked a bit at first as it just trickled past the floor boards and into the dirt until all the joints swelled up and became water tight. I thought of putting a drain in the floor under the tub to capture any leakage. I thought about making it out of 5 or 6 quarter teak or similar with massive sliding dovetails in all the side joints and glued with west systems epoxy but with the bottom which meets all for sides, 2 of them are going to be a cross grain application! cant glue that! Then, I thought from my experience building a stitched up wood kayak where the African mahogany was covered in 1 layer of fiberglass and saturated with a few coats of epoxy. Below the waterline was painted but the top I wanted to show off that beautiful wood so it was just varnished over the fiber glass-epoxy. And it did look like natural wood. you couldnt see any fiberglass unless you got your nose up to it. the fiberglass ( normaly white looking) disapears as soon as the crystal clear epoxy hits it. The varnish is for uv protection. so this was a thought. Line the inside with fiberglass and epoxy and make the sob watertight. This would give the illusion of having a zen like experience in your tub.,,, scratch that idea,, I live in a third floor condo and cant afford a flood to my downstairs neighbors. when I figure this out I'll write you.

[Craig McCormick]

I have a ceder soaking tub and the staves just butt together. The bottom slips into a dado at the end of the side staves. Three steel bands around the tub to snug things down/together. When you first fill them they do tend to leak a lot of water until the wood swells up. This takes three to four days for the leaking to stop. Mine has a submerged aluminum fire box for heat.

AZCRAIG

[Rob Sack]

I should clarify, that the tub I want to build is a tradtional Japanese rectangular soaking tub, so a "coopered barrel" approach won't work. I can't seem to find out how those made in the Japanese style connect the floor to the side and end panels. Also, if the end panels are let into dados cut into the sides and if the joint is tight enough not to leak, will the expansion of the end panel once it gets wet blow out the dado?

[Larry Edgerton]

There was an article some time ago in the West System news letter on a tub. Maybe they have a online archive?

Would be interested to see what you come up with.....

Larry

[Sam Murdoch]

Start thinking "boat hull" - off to work now but more later.

[Eric DeSilva]

I seem to remember the 200+ year old 1 person ofuro at my grandparent's place being circular and made out of iron. You actually built a fire directly underneath it.

[Sam Murdoch]

I should clarify, that the tub I want to build is a tradtional Japanese rectangular soaking tub, so a "coopered barrel" approach won't work. I can't seem to find out how those made in the Japanese style connect the floor to the side and end panels. Also, if the end panels are let into dados cut into the sides and if the joint is tight enough not to leak, will the expansion of the end panel once it gets wet blow out the dado?

I've been thinking that I would be building a coopered barrel type hot tub, but I might rethink that and build a square or rectangular tub. I installed a teak one a few years back for a client and it was a beauty. Sadly, I didn't really study the construction. Building the box, I think, would be pretty straightforward - plank sides and ends T&G or with tight splines.

The planks would all run horizontally so any expansion/contraction would be symmetrical - all free to move to the top edge. Think boat building as I suggested earlier in that the ends could be dadoed or rabbeted into solid wood corner (like planks to a keel/ stem assembly). We could also run the sides or the ends long and connect the mating planks with splines. I think in a pure Japanese example they would not use epoxy between the planks but rather pin through 3 or 4 T&G planks with wood dowels or "trunnels"aka, tree nails. I don't see why we couldn't assemble all the sides and their connections to the corner posts or splines with epoxy though. We could use bronze nails in the corners with nice decorative effect.

Now the bottom has me stumped. My first thought was to rabbet the bottom into the 4 sides much like a drawer bottom. No matter which way we orient the planks they need to expand and contract and locking in a bottom this way doesn't allow for that action. Of course an easy cheat is to use a bottom fabricated with marine ply, hmm ... Then I wonder about building the plank bottom so that it fully overlays the sides. Spline that connection too, all around and easing the edge of the bottom to the side so that (more boatbuilding) we could caulk the seam with tarred oakum (we'd have to keep our heat source away from the tar . Obviously, I am not finished working out this detail. Someone has already invented this wheel - just need more research. Hopefully others here will chime in with ideas.

Mine won't be teak, more likely some type of nearly clear cedar, but, I'm likin' the idea of such a project. This kind of what you had in mind Rob?

[Dick Aubochon]

I am interested in building a Japanese soaking tub, but am having difficulty finding any information of what type of joinery would produce water tight joints, especially in joining the bottom to the sides. Any suggestions or sources?

Check with Chris over at the Carpentry Way blog.

[David Wong]

You can get some ideas of one example of joinery from here.

[Steven Green]

I do know that the floor of the tub in Japan is seated in a dado called a croze and the croze is pasted with rice flour dough prior to seating the floor or the bottom. I got a mashed finger out of that learning experience when I was in the Navy. We filled the thing with water and my host added water every day till the tub stopped leaking like a watering can. Best of luck with it and let us know how you progess please.

[Craig McCormick]

I would love to have that style tub! I do love my snorkle hot tub. I dont need noisy water jets. Just hot water and peace and quiet while soaking. Once I get it hot on Friday night it doesn't take much firewood to keep it hot through Sunday. I love having a wooden tub.

azcraig