which exterior plywood for false floor

I have read a lot of threads and can't seem to find a straight forward link to the plywood i need to buy from lowes. I am going to coat it in Thompson's water sealer and put carpet over it. Could someone post a link to which 4x8' sheet of plywood i need to buy from lowes. It would make my life so much easier lol

Exterior rated BC plywood should be fine. Just seal it well. half inch or 3/4 inch would work well according to how much support you build in.

I am going to just lay it over the massive ribs on my Alweld. Going to put foam in between the ribs for support

Could someone tell me what BC plywood is. Im looking on Lowes we so and dont see it. All i see is pine, birch, oak, and hardwood?

Wood 101, todays subject BC Exterior plywood
BC is the grade of the plywood not what type of wood it's made from. The higher the grade, the less knots and voids the wood will have. In this case BC means that one side of the plywood is B grade and the other side is C grade. So one side will be prettier than the other. :mrgreen: A = no knots/splits and it's smooth/sanded B = knots with holes/splits filled and it's rough/unsanded C = knots holes/splits and it's rough/unsanded D = don't even go there, max allowed defects. The grade can also affect the strength of the wood since a C grade would have knots/holes/splits, it's obviously going to be weaker as a result of those defects. Exterior in the grade refers to the glue used to bond the layers of the plywood together. A glue that will not break down in moist environments was used in this case so it gets the Exterior rating for use outdoors. Of course you're most likely going to be using pine plywood for your boat project but you can go with a hardwood like oak, birch, or walnut if you really want to blow some bucks. :lol:

Thank u professor. Very informative

erictetterton said:

Thank u professor. Very informative

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LoL being a carpenter all these years has finally been useful for something I guess.

Mention that B/C will be the prettier pine ply. It's stamped B/C right on it.
I would varnish if I was in a hurry. Epoxy if not.
Get the edges good. 1/2 should be fine. I used 1/2 and my supports were 20" apart.
Keep a space between the hull bottom and foam if possible even if it's only 1/4". Hulls hate trapped water.

rabbit said:

Mention that B/C will be the prettier pine ply. It's stamped B/C right on it.
I would varnish if I was in a hurry. Epoxy if not.
Get the edges good. 1/2 should be fine. I used 1/2 and my supports were 20" apart.
Keep a space between the hull bottom and foam if possible even if it's only 1/4". Hulls hate trapped water.

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How would you keep the space?

Jeffrey said:

How would you keep the space?

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I wondered the same thing during my floor installation because I had heard so much about needing air flow to dry the water and drainage so water didn't stay trapped between the foam and floor. I came up with my own solution that I hope will work but only time will tell. You can see what I did in my build thread linked in my signature.