Where is the waterproofing layer in an older (victorian) wood tongue & groove porch deck with another porch or living space below (i.e. you do not want water to flow thru the deck)? Does the T&G wood serve to keep the water out or is there a roofing type membrane below with the wood decking "floating" above it? If so, how is the decking attached?
The porch has a roof above so it does not get direct rain but does get wind-blown rain.