Teak Deck Underlayment

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Narska
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Teak Deck Underlayment

Post by Narska »

Hi All,

I took up my teak deck and replaced the marine plywood at the bow, witch was rotted. Im getting ready to put down the teak again.

Is there some sort of waterproofing membrane that should be painted over plywood before the teak goes down?

I was thinking of RedGard, but have not been able to find any definitive answer.

The guy at the marina shop said that I should paint the plywood with resin.

Thanks in advance for the answers and advice,

-69 Trojan Flybridge
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gitchisum
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Re: Teak Deck Underlayment

Post by gitchisum »

Covering the plywood in resin is good advice. Better plan than using Red Coat. I used that in my shower under the tile, and would still rather use resin for the boat.
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Big D
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Re: Teak Deck Underlayment

Post by Big D »

I'm assuming by the vintage that this is an all wood boat? Regardless, the best thing to use is epoxy. In fact, it's best to lay the teak down into thickened epoxy without using permanent fasteners. Screws and washers are used in the gaps between the strips to hold them in place while the epoxy cures and are then removed, and the holes and gaps filled with epoxy. This way, there are no fasteners penetrating the deck that will again loosen and allow water intrusion. Check out the maintenance manuals available from West System, they're really informative and a must have for the wooden boat owner or anyone contemplating woodwork on board be it structural, cosmetic, liquid proof boxes, etc. Here is a copy of one of them. In the deck section, you'll see the method I'm talking about.
https://www.google.ca/url?sa=t&rct=j&q= ... OLuc9YXR6Q
She was a 1969 36 ft wooden beauty with big blue 440s that we'll miss forever.
And thanks to the gang, 2012 Trojan Boater Of The Year
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captainmaniac
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Re: Teak Deck Underlayment

Post by captainmaniac »

Big D wrote:I'm assuming by the vintage that this is an all wood boat? Regardless, the best thing to use is epoxy. In fact, it's best to lay the teak down into thickened epoxy without using permanent fasteners. Screws and washers are used in the gaps between the strips to hold them in place while the epoxy cures and are then removed, and the holes and gaps filled with epoxy. This way, there are no fasteners penetrating the deck that will again loosen and allow water intrusion. Check out the maintenance manuals available from West System, they're really informative and a must have for the wooden boat owner or anyone contemplating woodwork on board be it structural, cosmetic, liquid proof boxes, etc. Here is a copy of one of them. In the deck section, you'll see the method I'm talking about.
https://www.google.ca/url?sa=t&rct=j&q= ... OLuc9YXR6Q
+1

Big D is the guy to listen to and learn from when it comes to woodies. My folks had a 1969 28' Sea Skiff and we went through similar issues with deck and other wood rot issues that I have some thoughts about that I can share as needed, but Big D is the forum's woodie expert. (and expert in many other areas too!)

Just one comment though - if you do decide to use epoxy to seal things, do not fully encapsulate the wood. If you fully encapsulate it, and a crack ever develops in the epoxy, water can get in and rot the wood inside - and that could be 'not good'. I have seen a wooden mast on a sailboat - encapsulated in resin - snap as water found a way in and the mast itself was actually mush. Use epoxy to seal, but not encapsulate. If moisture makes its way through the epoxy, give it an escape route.
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Big D
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Re: Teak Deck Underlayment

Post by Big D »

There are pros and cons to encapsulation. The con is as CM mentioned; if water ever gets in, it'll never get out on its own. Having said that, if encapsulating is done correctly, proper fastening techniques adhered to, and regular maintenance and inspection performed, you shouldn't have that problem. Hi stress structures are especially vulnerable for obvious reasons, but again, it boils down to the above.

If done right and wetted out properly, even if the outer layer of epoxy cracks, the epoxy's penetration into the wood's fibers basically creates a top layer of plastic in the wood below its outer surface thus forming a protective layer in the wood itself both at its surface and slightly below. How deep the penetration depends on a few factors such as application techniques and wood type/density. Failures, more often then not, are due to compromising this layer. That is typically due to improper fastening techniques. If you don't take proper measures to seal fasteners properly, eventually water will get in past the epoxy penetrated layer in the wood, and that's when the problems begin.

It's common to hear folks say that you shouldn't completely encapsulate a piece of would because you need to let it breathe. NO YOU DON"T! In fact, fully encapsulating makes the wood more stable by preventing outside influences from having an undesirable affect. A perfect example is the fastening discussed above. A fastener in a stable piece of wood will hold its position much better and longer than in a piece of unstable wood. The more unstable the wood, the quicker the seal around the fastener or a joint will fail. This movement and flex, is what kills wooden boats because it eventually leads to loose joints and fasteners that let water into the wood deep enough that it never gets out, this promotes decay. This is why planks on a wooden boat have to be completely refastened once or twice in its lifetime if you want it to last. Some high end wooden boat manufacturers now completely encapsulate every piece of wood in the build before it goes into place. Of course after that, it's up to the owner to ensure he uses proper techniques when he installs something. It's like installing a transducer through a cored hull, or something on your deck, you can simply caulk it then deal with the consequences later, or you can do it right and never have to worry about it again.

Having said all that about minimizing movement, there are circumstances where it's not desirable such as when it's adjacent or a attached to a structure that does still move. That creates a stress point that will likely fail quicker but that's for another thread!
She was a 1969 36 ft wooden beauty with big blue 440s that we'll miss forever.
And thanks to the gang, 2012 Trojan Boater Of The Year
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Narska
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Re: Teak Deck Underlayment

Post by Narska »

Thanks guys great answers.

I used west system epoxy, and that stuff is really amazing and easy to work with.
rickalan35
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Re: Teak Deck Underlayment

Post by rickalan35 »

Great description, Big D

Rick
Trojan 1994 370 Express, 502 Bluewaters
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