I have a pool house with a t&g fir floor on the covered porch area. the pool house and porch area is above a full basement with a concrete floor. I primed all the wood before I put it down and then painted (the top only)it with oil based exterior floor paint. I am having a problem with the paint peeling off and the the floor is now leaking which is causing more moisture in the basement.

I like the looks of the "old time" porch floor but I need to do something. Should I have painted the underside of the flooring to prevent the moisture from pushing the paint off? Is it too late now. I'm considering some type of epoxy paint or a rubber membrane to go over the flooring and seal it.

Any suggestions? thanks