Concrete Waterproofing Alternatives

Crystalline concrete technology eliminates the need for separate membranes
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Sponsored by Xypex Chemical Corporation
By Peter J. Arsenault, FAIA, NCARB, LEED AP

Using Crystalline Technology in Existing Buildings

Water leaks often happen in concrete walls in existing buildings, particularly below grade. Of course, that means, the “positive side” (exterior) of the concrete is likely buried and not readily accessible. Hence, “negative-side” (interior) waterproofing is typically undertaken on the inside face of the concrete. Although water may still penetrate the exterior surface of the concrete, with this approach, it will be prevented from reaching the inside surface without impacting the interior of the building or any spaces/functions/materials found there. Of course, protection against concrete deterioration is not achieved as with positive-side treatment, but water penetration stops at the interior side of the concrete so the inner surface is protected. The degree of protection and the effectiveness of the interior coating will depend on the product used. Some are simply painted applications that may hold up for a while but are not guaranteed for more than a few years.

A crystalline waterproofing system was used on the negative-side interior walls of this below-grade parking structure. A fountain complex is located above this garage, which introduces water into the surrounding subgrade.

Crystalline Renovations

The preferred choice for negative-side waterproofing is to use crystalline products that are applied from the inside. These are provided in powder form, mixed with water on-site, and applied as a cementitious slurry coat to above-or below-grade concrete. The intent is to cover the entire inner wall surface and thus create the conditions for the crystalline chemistry to diffuse into the substrate and create a continuous water seal. It can be a single coat or the first of a two-coat application where recommended by the product manufacturer.

Like any field applied product, surface preparation is obviously critical. The slurry coat can be applied to wet surfaces, but the existing wall needs to be intact and stable enough to receive the coating. In some cases, removing loose or damaged pieces may be necessary followed by appropriate repairs. Providing water plugging or other measures for large holes may also be called for. All of these steps require the judgement of a design professional and the skills of tradespersons to do the needed work.

The application of crystalline coatings on existing buildings yields all of the same characteristics as when installed on new construction, plus some other notable ones as follows:

  • Wet or dry application: Crystalline applications do not require a dry surface for installation. This is particularly helpful in conditions where dryness would be difficult or impossible to achieve.
  • Simplified preparation: Compared to some other alternatives, there is no costly surface priming or leveling needed prior to the application
  • Durability: The finished treatment, when installed properly, is not subject to deterioration from either the inside or outside as other coatings may be. Hence there is typically no need to plan on replacing it after several years.
  • Cost: Crystalline treatments on negative-side surfaces are less costly to apply than most other methods, particularly over the remaining life of the building.


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Originally published in Architectural Record
Originally published in December 2019