Quote Originally Posted by ed21 View Post
T&G boards will always leak unless their is some kind of waterproof membrane underneath.
Proper drainage as mentioned is also needed.
Caulking the boards won't work for long. Too much expansion & contraction.
The type of board is less important than the waterproof membrane & drainage.
Tar paper won't work as a membrane.
Couldn't have said it better. Good answer!