Waterproof/Water-resistant Finish for Bath Shelf

[Richard Amabile]

I recently helped my son make a bath shelf as a gift. It is made of a single 3/4 inch piece of pecan and is 15 inches wide by 29 inches long. Three stringers are across the width to inhibit cupping. The shelf spans the tub from side to side so that people can place a book, or Ipad, etc. on it while soaking in the tub.
The wood (pecan) will not be stained. It has been sanded to 220 grit. What is the best finish to put on such an object given the fact that it will be used in a hot steamy environment, will be handled with wet hands and may have water splashed on it from time to time? Right now I am considering using Waterlox Original and putting at least 3 coats on it with a brush to build it up. My recollection is that such a finish would take at least a week to dry after the last coat before being put into use. From what I have read it appears to have the best water resistance of the various finishes. But, this is the first time we have made an indoor piece that would be subjected to such a wet environment.
Any thoughts on what finish would be best on such a piece would be appreciated.

[Howard Acheson]

First, do NOT add any cross grain support that is intended to prevent cupping. The sold wood shelf will expand and contract with changes in moisture content. Of course, something like you are making will be very subject to changes in moisture. If you have a cross grain support, it will restrict the expansion and contraction of the bottom of the shelf if the cleat is glued or tightly screwed onto the shelf. This will actually CAUSE the shelf to warp. It is probably unlikely that your shelf will warp if you just don't attach and cross cleats. It you fell you must have the cross cleats. attach the cleats with screws in elongated holes that allow the expansion/contraction to occur freely.

It is a basic rule not to use a cross grain construct unless it is designed to allow free movement.

[Richard Amabile]

Howard:

Thanks for the reminder! I completely forgot about needing the elongated screw holes if I do use the cross grain cleats. With your advice I may just leave them out completely.

Thanks for the input.

[Scott Holmes]

Although I generally don't recommend an exterior finish for an interior project... 15" wide pecan may move enough to crack the harder interior finishes. Howie what do you think about Waterlox Marine or Epifanes in this application?

[Howard Acheson]

>>>> what do you think about Waterlox Marine or Epifanes in this application?

Scott, I think either would be fine. I too, am not a fan of exterior varnishes on interior applications. However, the very moist environment will cause movement and, as you know, the primary positive attribute of exterior varnishes is their ability to stay adhere as the wood substrate expands and contracts. I would recommend that the finish be given 4-5 weeks to fully cure before it is mounted in the bathroom.

[Mike Henderson]

Wood is probably not the best material in such an environment. No matter what finish you put on it, water will get through. Eventually the finish will develop cracks and then you'll have water stains under the finish.

You can work Corian (or equivalent) material with woodworking tools. That would be a much better material for a shower.

Mike

[Otherwise, I'd go with something like teak and not put any finish on it.]

[Paul R Miller]

Look into S1 sealer from System Three. This is a very thin epoxy that actually penetrates the pores of the wood and then crosslinks to form about the best seal you can get on wood. I've used it on all sorts of boat applications and never had a failure that I could blame on the material.

[Richard Amabile]

Thanks for all the suggestions. They help quite a bit in determining how to proceed on this project as well as what to consider for future projects of this sort.

Richard