Is it better to waterproof a basement from the outside or the inside? I've heard different things about this. We have a home built in the 40's on a cinder-block foundation. One side of the house is inaccessible without removing our driveway.

  • 3
    It's more difficult and more expensive on an existing home, but outside is always better.
    – Tester101
    Aug 30, 2011 at 11:57
  • 2
    As a note - we followed this advice, and have not regretted it.
    – Kyle
    Jan 30, 2013 at 4:15

2 Answers 2


When applied correctly, I prefer waterproofing from the outside. It keeps the water out of the concrete, rather than permeating up to the interior water proof layer. If it's allowed to freeze in the foundation, you could have cracking.

In addition to water proofing the foundation, you also want a weeping tile or French drain around the foundation anywhere that water may not naturally run away from the home.

That said, as you're seeing, fixing this issue from the outside can be much more difficult, and therefore expensive. Another factor is if you need to use a sump pump to move water from any drains up and away from the home. If that's the case, you also need to consider if you want this pump indoors or outdoors.

  • Could not have said it better, and yes, I did try. +1
    – KeithS
    Sep 6, 2011 at 21:52

If you are getting water as soon as it rains, within 20-30 mins and it stops coming in after the rains stops, within 20-30 mins, then you have a surface problem and should look at your gutters, leaders, and grading.

If water comes in hours later, half a day later, then it's the water table rising and putting hydrostatic pressure on your slab and foundation and you will need French drains to permanently stop it from coming in.

See this article on my company's website for more information: http://www.aridbasementwaterproofing.com/index.php/blog/comments/an-inside-or-outside-problem

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