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Community and Q&A

Exterior foundation waterproofing

Chrisroche | Posted in General Questions on

I recently had my foundation wall treated with a spray on waterproofer. I noticed a week later that there were little pin pricks throughout the black layer. Some of the pin pricks you can see concrete through. Is this a typical occurrence or should I have the company spray the wall again? I am mostly worried that it will cause the waterproofing to be defective due to moisture instrusion. Thanks!

[Editor’s note: Photo below.]


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  1. Chrisroche | | #1

    I took a picture of what it looks like. I may just be overly cautious. I hosted the picture on

  2. Expert Member

    Asphalt-based emulsion, and most other exterior foundation treatments, are really better called Damp-proofing, not Waterproofing. They are designed to stop large amounts of moisture migrating through the concrete, but not all of it, so small imperfections like you see are pretty common.

    What will materially affect it's efficiency is the way you backfill and how diligent you are in installing your perimeter drain system. Pay attention to these any you will be fine.

  3. Chrisroche | | #3

    Thanks for the advice. I was told it was waterproofing liquid membrane, but it sounds like there is some ambiguity to what products are out there and how they should be classified. It was House Guard

  4. Expert Member

    Sorry - from the picture I thought it was typical asphalt damp-proofing, not a liquid membrane.They are designed to stop hydrostatic pressure, so holes matter. I'd have the installer back to look at it.

  5. Sal_123 | | #5

    I looked for a true spray-on waterproof product that I felt would work and found none. The word "waterproof" is thrown around very liberally when it comes to spray-on foundation products. I ended up going with Grace's Bituthene. It is a peel and stick membrane applied to a primed wall. Was applied on a hot day in Aug last year. The material adhered well beyond my expectations. I ran it long and gave myself a 3" overhang on the inside of the foundation wall all around using it as a sill gasket membrane and capillary break. It was not cheap, but highly recommend it. In your situation see what the installer says, consider re-application vs going over it with a membrane product. If you go over with a membrane product, check the with manufacturer regard the compatibility and adherence of the membrane with the spray-on product.

  6. RobInNorCal | | #6

    Years ago, I built a home using Thoroseal, a brush-on cementitious coating now owned by BASF. The product is marketed this way: "MasterSeal 582 is...a waterproof portland cement-based coating for below-grade exterior concrete and masonry surfaces. Polymer-modified with MasterEmaco A 660, MasterSeal 582 creates a cost-effective durable waterproofing barrier
    Recommended uses: Exterior, Below and above grade, Foundations, Exterior above-grade as a waterproof base coat for high-build acrylic coatings, Concrete, Masonry."

    It seems to have done the job for me, but what do I know? Do any of you have a POV about this product or its similar competitors? It's quite a bit less per sf than some of the crystalline compounds that are often referenced elsewhere on this site: materials cost is ~$.30/sf, and labor seems to be comparable to all of the other brush/roll on compounds.

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