These excerpts are taken from message threads at our online forums. To browse — or, better yet, join in the conversation yourself — visit and click on Forums. — The Editors Slab Waterproofing •Posted by Al: A foundation contractor told me that he uses a waterproofing additive in the concrete when pouring a slab-type foundation instead of a vapor barrier. He claims that this is a better procedure because a vapor barrier doesn't seal around plumbing, gets punctured, tears, etc. I am interested if anyone has found this to be effective. •Followup posted by Keith: I'm not aware of any additive that will "waterproof" concrete. Higher-strength concrete will become less permeable