On Jul 2, 2:37*pm, Vic Smith wrote:
On Thu, 2 Jul 2009 05:33:59 -0700 (PDT), jamesgangnc

wrote:
On Jul 2, 12:27*am, "SteveB" wrote:
I live in a dry area. *I want to replace some wood on my boat. *Is marine
plywood an absolute necessity, or would a good grade of sanded one side
suffice? *About the only time it would get wet would be when it is outside
and it rains, and we get less than two inches annually.

Steve

Marine grade plywood typically has the voids filled as each layer is
added. *You see the void filler on normal plywood only on the outside
layers. *When I replaced my floor I selected a plywood that was not
pine rather than focusing on marine grade. *Right or wrong, I left the
underside unsealed so that it could dry when it got wet.

Don't know the answer to whether or not to leave the underside
unpainted on a boat floor.
But when I rebuilt an outside porch once with tongue and groove pine I
primed/painted both sides.
Wouldn't believe how fast that floor rotted.
You probably did it right.

--Vic

He did.. In the old days they used to "encapsulate" wood with epoxy.
Water will get in, and the result will be it can't get out..