As I write this, it has been raining for a month and many who have a perpetually wet basement or garage are fed up to the point of doing something about it.  I hope I caught you in time to advise against one of the many ineffective waterproofing schemes out there.  Waterproofing by itself is rarely effective, and waterproofing applied on the inside of a slab or foundation is never effective.  Water is relentless and inexorable.  Even a system 99.99% effective will not keep you dry.  The water will eventually find the flaws in the system, and to my knowledge (forty years experience), there is no perfect system.  This was made apparent to me when I had the opportunity to visit the interior galleries deep inside the Glen Canyon Dam.  We were over 100 feet below the surface of the lake and even with 20+ feet of high quality concrete between us and the water the walls leaked and the water had to be pumped out.  Waterproofing applied to the outside has a better chance to succeed, for the pressure of the water pushes it into the wall, but anything applied inside will be pushed off by the pressure of the water.  The only way to have a dry basement is to give the water someplace to go other than your basement.  The walls and slabs must be drained.  There is no other way.

The traditional drainage system is a French drain on the outside at the base of the wall.  In an urban area such as ours, with zero lot line building, there is no way to install such a system, so many homes in the Bay Area don’t have any drainage system at all.  The subterranean space was never intended to be living space and seasonal wetness was acceptable.  With our modern lifestyles we often want to utilize these basement spaces.  In my next post I will describe the scheme I have used with great success, retrofitting it into existing buildings, even those with water visibly flowing through the space.  They are dry as a bone year after year, no dampness, and no mold,


  • Michael,

    You make an excellent point about the evolving intended use of basements. One of the more difficult “load cases” an engineer or designer might consider is the unanticipated re-purposing of the facility by some future user. Sometimes, if an engineer designs for an unanticipated use, such as including effective drainage and waterproofing in a basement not originally programmed as living space, there are accusations of “over-engineering.” But when that same basement is later converted to habitable space and no expensive retrofit for waterproofing and drainage is required, very significant savings are realized.

    Another point of yours I agree with: Subterranean waterproofing without drainage is incomplete. I don’t think waterproofing in and of itself is bad, though. It is part of a system that includes drainage and other aspects of protection that, taken as a whole, are effective in keeping the outside outside.

    – Joshua B. Kardon, SE

    • michael

      I agree Josh waterproofing never hurts but without drainage it rarely works and with good drainage it is usually not necessary. However when possible I apply waterproofing to the outside. Belts and suspenders never hurt.

  • Without proper drainage all that work of waterproofing may not be of much benefit.
    I agree that the outside needs to be carefully considered if you find you have a problem with leakage in the basement.
    A friend of mine who has an old house, about 60 years old, just had to re-seal his basement. It ended up costing him $17,000 to get the job done properly. They had to dig a trench all the way around the outside of his house to seal it up.

    Problem today is that people are unwilling to spend that kind of money to get the job done right.

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