Teak expansion and shrinkage

[Charles Mercer]

Hi,
I am laying a teak veneer deck over ply at the warmest driest part of the year here in northern California. Is it necessary to anticipate expansion between the 2 inch wide strips when the wet rainy season arrives, or should the strips just be butted tight? The seams will be filled with a two part poly sufide. The area I am working on is the cockpit and the widest section is about 30 inches. I just want to avoid any buckling between the planks.

[Andrew Craig-Bennett]

I was about to say "Hooray, something I know about, at last!" but actually I don't know the answer to this one, save that the Gougeon Brothers say that THIN teak (I fancy they say up to 3/16") can be laid with no allowance for movement, because the glue overcomes the tendency to move in the thin strips. I don't quite understand you when you say you are using a 2 part polysulphide in the seams, yet you are butting the strips tight.

[Jamie Hascall]

I think you might want to give just a little space between the planks when you lay them, say the thickness of a piece of posterboard every so often. That way you will not have any possibility of buckling. That said, the amount of expansion you'll get over 30" is probably pretty negligable. Since you will be filling the rabbets with two part polysulphide while the deck is very dry, it will always be under a certain amount of compression and thus very unlikely to fail due to the shrinkage of the wood. I happen to really like the Smith's two part Poly with CPES as a primer. Two part is a pain to work with, but after doing my deck twice, I can say it's worth the trouble.

Good luck,
Jamie

[ 09-18-2002, 02:11 PM: Message edited by: Jamie Hascall ]

[Scott Rosen]

Since it will not be a true laid deck, you will be depending on the polysulfide, not the fit of the joints, to keep the water out. I agree with Jamie.

[Bruce Hooke]

Picking up on a couple of points that others have raised:

1. How thick is the teak? This will make a very big difference in how much it will actually shrink and expand.

2. How is it attached to the ply? I would expect it to be epoxied down but if that is not the way you are planning to go this would also be an important issue in relation to your question. If it is epoxied down then I don't think you need to worry about the edges lifting no matter how it is cut.

[Charles Mercer]

The teak is 3/8 thick and just over 2 inches wide with verical grain. I haven't yet decided to go with epoxy or bedding the strips in some sort of polysufide and screwing them down. The previous deck lasted almost 30 years without the epoxy. The boat is a Mariner32 ketch. Fiberglass hull and wood cabin.

[Bruce Hooke]

IIRC 3/8" is a good bit thicker than what Gougeon recommends as the maximium thickness for epoxying down teak deck strips so that would suggest that polysufide might be the better way to go unless you want to consider going a good bit thinner on the teak strips. If I were using 3/8" teak strips in set in polyglop I think I would still coat the plywood with 2 layers of epoxy so that if water makes it through the seams and the bedding it is prevented from getting into the plywood...

[Meerkat]

Art, that's beuuuutieful! A Haven 12 1/2?

Always did like straight laid decks smile.gif

[Art Read]

Charles... Your teak strips are just about exactly the same dimensions I went with. What Bruce suggests:

"...polysufide might be the better way to go unless you want to consider going a good bit thinner on the teak strips... If I were using 3/8" teak strips set in polyglop I think I would still coat the plywood with 2 layers of epoxy so that if water makes it through the seams and the bedding it is prevented from getting into the plywood...",

is exactly the way I did it. She isn't launched yet, of course, but the deck "seems", (no pun intended), to be holding up beautifully so far... No signs of movement.

http://www.imagestation.com/picture/sraid21/p6160b6f097116509be6b3edc4674ac78/fdb12197.jpg

There were a few, odd dips and hollows that the teak had to comform to in some of the transition areas around the cockpit opening, but that 5200 bedding I put it down with appears to be holding those strips with a death grip. (I did "scuff up" the cured epoxy coating on the plywood subdeck a bit and treated the undersides of each teak strip with CPES before buttering it up with the goop, and then I "cleaned up" and filled the seams between each plank with a purpose made deck seam compound.)

[Art Read]

Whoops! Sorry, Meerkrat, I pulled an "edit/delete" on you... Actually, she's a Dark Harbor 12 1/2. I've taken a few "liberties" with the cockpit layout and deck construction, but otherwise she's as designed. Here's a link to an "Imagestation" page I've been fooling around with, if you're interested.

http://www.imagestation.com/album/pictures.html?id=4292219521&show_all=1&start=1

I like straight laid decks too. (Don't hurt that they're a lot easier to put down any either! ;) )

[ 09-19-2002, 03:03 PM: Message edited by: Art Read ]

[Bill Perkins]

I'm curious : If a builder decides to shim between boards is there any further reason for the rabbet ? Just use square edge stock and thicker shims ? My thought was that the point of the rabbet was that it registered directly against the previous plank without the need for shims .

[ 09-19-2002, 04:47 PM: Message edited by: Bill Perkins ]

[Jamie Hascall]

I agree with you on the issue of not shimming a rabbeted plank deck. My previous recommendation was inview of everything being put together in a very dry state and then heading out into a wet No. Cal. winter and doing a belt and suspenders approach. A little extra room for expansion couldn't hurt. Doing a spaced plank deck probably gives more adhesive surface area on the sides of the joint and thus a greater overall tenacity. It's just more of a pain to do. Smith's recommendation for new decks is to bed the whole deck on a layer of their polysulphide and shoot the seams with it too. That way you have a continuous membrane of the stuff with the wood protecting it against wear. I think it sounds like as bulletproof a method as I can imagine. The stuff's expensive but a sealed deck is priceless.

Jamie