Building a Curved Bench for a Steam Sauna

Advice on glue and wood choices and assembly methods for a curved bench in a hot, moist environment. July 30, 2009

I need to build a bench for use in a custom steam shower. The shower enclosure is 6' x 6' with a 4' 6" radius curved wall on one side. The bench will be straight for 18", then follow the 4' 6" curve and then go straight for another 18" at a right angle to the first straight. I'm thinking about doing a laminate of 1/4" x 3" slats to form 1" x 3" curved seat slats separated by about 3/8" of air space (or water drainage).

This will be quite a bit of work to construct, so I really want to pick the right wood and the right glue for a steam shower environment. Also, a deeply colored wood would be a nice fit with the decor (Brazilian Teak, Redwood, etc.) Any thoughts on material selection?

Forum Responses
(Architectural Woodworking Forum)
From contributor J:
I'd say teak, ipe, or angelique if you could find it. For adhesive I think I'd go with West System epoxy. Titebond 3 should work, but not sure I trust it that much. I would try to minimize glue joints nonetheless, and use bronze or stainless fasteners where possible.

From the original questioner:
What I read about teak and ipe for strip laminate curves on this forum made me count them out at the get go. I like both woods for the wet environment, but I'm hesitant to consider them (especially ipe) for a bent strip lamination project. What do you think about some clear all heart tight grained redwood?

From contributor J:
I don't know about the redwood. The Finns use a lot of cedar in the saunas, though. What about sawing those curves out of solid instead of stripping? It may use a little more lumber but should take less time. That's a pretty big radius and you can certainly get wide teak.

From contributor R:
Teak is and has been used in boats forever. Why do you dismiss it as a bending/laminating material? A bent strip lamination in teak, using epoxy, will work fine. Cypress will also work well in a wet environment, but is typically pretty light color. Sinker cypress, on the other hand, can be had in darker shades.

From contributor L:
Does it need to be bent? If you can just use boards cut to the curve it would be easier and quicker. You wouldn't have to worry about so many glue joints that may or may not fail because of the hot and wet environment. Redwood would be fine and using the West System would be overkill, but it would work well. You could get away with TBII or III and still have it perform well. And the dry time would be much less.

From contributor A:
The cost of teak is rather high. We all know the epoxy will work. We all do not know if TiteBond3 will work. Why not spend a little time and a few dollars on a product that will work?

From the original questioner:
Thanks for all the great responses. Teak is sounding like a really good option. As long as the finished product is beautiful and has a long service life, I'm not concerned about the cost of material or the time in building. My biggest concern is for stability of the product in a steam shower environment that will have massive swings in temperature and humidity.

From contributor D:
You might consider Resorcinol glue. This gives a dark purple glue line and is the original waterproof glue. I used to make boat doors for the Chris-Craft restoration trade, where teak and resorcinol was the original work and the replacement. As long as the glue was warm and kept warm until cured, it was bulletproof. We never even fussed over wiping down with acetone, etc. Glued for width, thickness and mortise and tenon joints. The glue line is rigid.

From contributor E:
I'm with contributor J - I'd try to minimize or even eliminate any type of glue joint. I'm not sure that any adhesive manufacturer will warrantee their product for a steam shower type application. Mechanical fasteners are a better bet. As for a wood species, I'd stick with what's proven.

From contributor S:
Aside from whatever the species of wood you select (teak) and fabrication method you use (strips, blocks and through bolts), make sure the bench is removable for easy cleaning.

From contributor C:
Weldwood Resorcinol Waterproof Glue is made for such an environment and has been around for decades.

From contributor R:
A lot of work, but mortise and tenon everything and peg the tenons at the legs where the stiles and rails intersect. If you offset the holes by about 1/32 you can use the pressure of the dowel to hole it together. That with some good waterproof glue and you should be fine. You might consider cypress. I know it is light in color but it is pretty much impervious to water. You may find a colorfast stain that will hold up to steam. Water would be less of a concern than the steam that will have the most effect on whatever you use. Also, if you are using this as a shower, remember you need to be able to clean the soap residue off, so some type of finish that will allow you to clean the wood. Sounds like a really cool project.

From contributor T:
So has anyone actually built a piece of woodwork that has been subjected to a steam room environment? Certainly the folks suggesting Titebond 2 or 3 haven't, as it wouldn't last the weekend. Epoxy would work until the wood expands and contracts enough to break apart around the glue joints. Steam isn't quite the same environment as boat work. Last time I checked the ocean wasn't so steamy and didn't get to quite as high temps as in a steam room regularly. Best bet would be minimal glue joints, no laminations and parts cut from solid stock. Even then, plan on replacing them once in a while as they deteriorate.

From contributor B:
I think contributor T hit the nail on the head. I have a steam shower in my bathroom and opted to not build in a stone seat. I built a simple bench made of leftover Cumara 5/4" x 6" stock. Two boards joined with a loose tenon set in mortises. Tenons are 3/4 x 4, also cumara. This assy for two legs and top. Top about 30" long legs at about 18", legs are stub tenoned into top, not through mortised. I left about 1/2" space between the boards for drainage. This was glued up with epoxy and no mechanical fasteners at all. Two years later and still holding. I leave it in there all the time, with steam and regular showers. Color is not so important, as it will go pretty grey on you. Color comes back 80% when wet, though. Still seems very stable and no wiggle as of yet.

From contributor W:
Seems like most of the saunas I see are cedar. CVG western red cedar seems to be the most common. That or redwood. I have some WRC that has some nice dark brown coloring.