Wood movement

[Jay Knoll]

Hi everyone, I need some help/advice!

I'm in the process of a bathroom remodel (pictures later Tyler!) one of the features is a bench at one end of our shower. I found a massive piece of Spanish Cedar, so that is going to be the bench, supported by some "bump-outs" on each of the shower's sidewalls.

I've been carefully fitting the bench this morning, (thank goodness the walls "toe out" slightly from the back of the shower) and trying to get as tight a fit as possible. I'm planning on finishing the bench with 6 coats or so of water based polyurethane gloss varnish and then running a small (I hope) bead of clear caulk around the top edge where the bench meets the wall.

The thickness of the bench is such that I have to slide it into the shower keeping it parallel with the floor until it rests on the bump out supports.

I'm wondering if I'm being too careful with my tolerances.

I seem to recall that wood movement is across the width of a board, not the length, am I correct? The board is 30" long, 14" wide (might become a bit narrower once we see how it feels in place), and 2 1/2" thick.

I don't want to crack the porcelain tile that covers the walls just because I decided to get the bench in as tight as I can,

Any advice will of course be appreciated!

I'm on to another phase of the project while I wait for your input.

Thanks

Jay

[Steve Clardy]

Normally there is no wood movement on the length.
Might give it an 1/16", 1/8" clearance anyway.

[Frank Chaffee]

Jay,
I would design for a caulk joint ~1/8” wide. Then I would route a groove that same distance from each edge to be caulked (yes, including where the bench rests on the bump-outs), and insert backer rod, so the cross section of caulk will be approximately square.
Frank

[Jay Knoll]

Thanks guys

I'm going to do it in steps, I've got it fit into the niche, going to just put a couple of dabs of caulk on the bump-outs to hold it in place and then caulk around the seat/wall joint using the gap that is there. If it fails, then I will try the routed groove approach. Things aren't perfectly square in there and I'm concerned that the routed groove will accent the "construction defects".

I've got plenty of thickness so if the varnish fails, I can always get down to "new wood" and refinish the slab.

Jay

[Jim Becker]

Jay, you're likely going to be unhappy with putting the finish on the wood...as soon as there is any break where water can get in (and you will have that happen...), you're going to get discoloration, etc. Do you really need a finish on it? (I'm not familiar with "spanish cedar" and it's properties)

[tod evans]

jay, yet another thing to think about; caulk will trap water...02 tod

[Jay Knoll]

Yes, I know I'm taking a bit of a risk, but the guy that I bought the cedar from says it is good for 100 years in water! They build boats out of it, in addition to cigar boxes!

I've done a fair amount of varnishing on boats I've owned and know the risk. Thought I'd try this rather than building a slatted bench (which will catch all types of crude -- I know from the shower seat we had on our sailboat).

So, if it doesn't work and/or refinishing takes too long I'll build something else.

The tile guys did a great job of gently sloping the supports so the front edge is lower, should help in drainage and a quick wipe with a hand to get the standing water off.

Here is some information on the wood

http://www.advantagelumber.com/spancedar.htm

Thanks for all the help

Jay

[Frank Chaffee]

Frankly Jay,
I think the best approach here would be to raise the cedar bench slightly from the bump outs on standoffs, and also leave a space to the shower walls.
Frank

[EDIT] …And if bolts were in recessed counter bored, pluggable holes so the bench could be removed….

[Jim Becker]

Further to Frank's comments, a slight slope will also take care of the water without requiring slats.

[Darrick Robbins]

Do you really need the caulking at all or is that what is holding the bench in place. I agree that the caulk would probably hold water, and if there is a slight gap around the outside then water will run down the wall instead of being directed onto the wood. Just a thought. Sounds like a good size shower.
Darrick

[Jay Knoll]

Well guys, great minds think alike! I've thought about everything you've suggested -- here is my reasoning for delaying and trying the "tight fit" approach.

If I leave a gap I'll need something to hold the seat off the side/back walls.

Water will run down and get caught on the bump-outs, and in Florida that is an invitation for mildew

Ditto for soap/hair etc gathering on the surfaces under the seat

The caulk is what will hold the seat in place I don't want to drill the porcelain tile and put plugs in the wood -- that will be an invitation for leaks

If I put something under and on the ends of the seat for standoffs, then we'll be fussing with the seat after each shower, picking it up, drying off the underneath surface etc.

If it doesn't work, then I can try the alternatives you've suggested, all of which mean making the seat shorter.

So I think I'll go with the caulk approach first and see what happens,

Heck, if that becomes too much trouble, we might just slam a piece of granite in there!

Jay

[Joe Jensen]

You don't need marine varnish as you won't be exposed to UV. But, you will want to make sure the varnish is a softer varnish that will expand and contract with the wood. If the varnish is a rock hard bar top type varnish, then it my crack...joe

[Frank Chaffee]

Frank

…If it fails, then I will try the routed groove approach. Things aren't perfectly square in there and I'm concerned that the routed groove will accent the "construction defects".Jay
Jay,
You may well be able to create a caulk joint that does not fail. To make myself clear about the routed groove for backer rod however, please know that this rod-in-groove would be beyond one’s view by ~1/8” on all surfaces that contact the wall and the bump out, and hidden by caulk.
Frank

[Howard Acheson]

>> 6 coats or so of water based polyurethane gloss varnish

I would re-think this. A waterborne finish is not very durable in a high moisture or wet application--particularly hot water. It rapidly deteriorates. You would be better of with a good marine oil based varnish. Nothing you find in a big box will be very good nor very durable. Go instead to marina or marine chandlery. Look for brands like Wolsey, Pettit, Z-spar or Epifanes.

Keep in mind that varnish is very slippery when wet.

[Jay Knoll]

Howie

Thanks for the heads up, I am using the waterbased on the vanity, want the "crystal clear" look on the maple. So I thought I'd use it on the seat as well -- the fast drying/recoat time is attractive!

Yep, checked with Minwax this morning, they agree with you, so I guess I'll break out the Clipper Clear marine varnish left over from varnishing my picnic table.

Jay

PS The tile guys are in grouting even as I type, so I better keep pushing so SWMOB will be happy.

[Ken Fitzgerald]

Jay.........I made an oak backsplash to match the oak vanity top the LOML picked out when we remodeled the bathroom. The water based finish on the backsplash was the first to go bad at the joint where the backsplash met the oak vanity top. The oak vanity top was finished in laquer.........eventually it went bad in the area where we use the waterpic...........:(

Good luck with your project!

[Jay Knoll]

Ken,

That won't be a problem, the top and backsplash are going to be granite -- if I have a water problem I will be surprised! The polycrylic was for the base/doors/drawers on the vanity


Jay