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Porch Decking

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.

Re: Porch Decking

The tongue and groove is not the waterproof surface. There has to be something over it, like roofing or tar. Without seeing it, I'd guess that there's a waterproof surface below the deck. I'd also suspect that the deck is suspended over the roof by supports that penetrate throught the waterproof membrane. Those penetrations must be sealed or you'll get leaks.

The other way it could be done is to build the deck right on top of the waterproof surface. People before you may have just nailed the floor joists to the surface of the roof. Bad. You could get leaks all over, wherever you put the nails into the roof. At least with the first method, above, you would know where the leaks come from and can address them, if you can get to them.

Decks over a roof are a touchy thing, regarding leaks.

Good Luck.

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