# Marine plywood



## hmdomn (Sep 22, 2008)

Anyone know where I can get a good deal on marine plywood in the Lansing or within 30 miles of Portland/Lansing? Is there a difference between the wolmanized wood and marine wood? The local marina is trying to get me to buy their 'marine plywood' for $120 for a 4x8 sheet! I know it isn't cheap, but $120 is a bit outrageous. :yikes:Looking to build a floor in a project boat.


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## jpollman (Jan 14, 2001)

Don't use pressure treated plywood in a boat!

I'm assuming it's an aluminum boat. If so, the chemicals in the treated ply will react with the aluminum and destroy it. If you're talking flooring, don't waste your money with marine plywood. Just use some BC exterior grade plywood and you can get it cut to size and then brush on some epoxy sealer and you'll be fine. It would be a complete waste to use marine ply to redo the floor of a boat IMO. For 4x8 3/4 BC ply you're looking at about $25 per sheet give or take a buck or two.

John


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## hmdomn (Sep 22, 2008)

Yes, it will be for a floor of an aluminum boat. I can live with $25 per sheet....what is BC? I just don't want something that is going to rot/bend after a year. The boat will see the elements about 50% of the time, so do would you still recommend the 3/4 BC plywood?


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## jpollman (Jan 14, 2001)

BC is just the grade. One side "B" is sanded fairly smooth and the "C" side is sanded but not as much. Just use the B side up and you'll be fine. If it's a floor and not decking, you may be able to use 1/2" but it's not going to be as stiff but will be lighter than 3/4. I was thinking deck and not floor. I got rid of a boat a couple years ago that had 1/2" BC exterior plywood floors and they were just bare ply and not treated with anything. They were in good shape and I had the boat for about four years and they were just as good when I picked it up.

Like I said, I was thinking 3/4 for a small section of decking but if you used 3/4 for a good size section of floor that would be pretty heavy. See if you can work out a way to use 1/2" and you should be fine for a floor. 1/2" BC exterior should be about $18 a sheet if I'm not mistaken but haven't bought any recently.

John


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## jpollman (Jan 14, 2001)

I was just thinking about it. The boat I had was a basic 16' open aluminum fishing boat. It had two sections of floor in it. One between the rear bench and the center and one between the center bench and the forward one. A previous owner had installed a home made side console so I couldn't remove the center section of floor but it was many years old and in great shape. The rear section of floor was just two or three 2x4's cut down to take the shape of the lower portion of the hull but the tops were flat and straight. Then the 1/2" plywood was screwed to the 2x4's and it worked great. I could just pop the rear section out if I wanted to. It worked very well and it was light and cheap to build I'm sure although I wasn't the one who built it.

John


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## jward (Feb 16, 2009)

Ok Let me see if I can explain this and not screw it up . There is wide range of "treated wood" there is different levels of preservaties in the wood depending on the rating of the wood . Most of the treated wood that can be found around here has a level of something like .05 % in it and it is rated just just for outside exposure. While its not commonly available around here you can buy a treated lumber that is rated for continuous salt water exposure and has a level of 5.0 in it . As you can guess the higher the rating the more it cost . True marine grade plywood is insanely expensive and as JP said the chemicals in new treated lumber will eat aluminum. You would be better of to buy standard ply and seal or paint it . Just my .02 . 


Jward


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## Sling (Aug 2, 2005)

go to iboats.com search the boat restoration threads....enough info for anything you need


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## MEL (Jul 17, 2005)

From my days selling Plywood for a Detroit based Wholesaler:

Marine grade will not have any voids other plywoods have voids.
Marine uses a special water resistant glue between the plys.
Marine will use other species of wood in its construction.

If you use other grades of plywood, make sure you fill in any voids with water proof filler. Make sure the edges are sealer really good!!


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