Damp proofing-Waterproofing Choices

damp proofing-waterproofing choices General:

There are a lot of damp proofing-waterproofing choices available to homebuilders and new home buyers today. This article provides some basic details regarding what can be expected from the products in various categories.

All damp proofing and waterproofing must start with a clean, smooth foundation wall. Loose debris,dirt and mud should be washed or brushed off, protrusions removed, and any existing cracks repaired. Fill or bridge cracks with caulk or seam tape, as approved by damp proofing-waterproofing product manufacturer. Concrete should be allowed to cure and dry as long as recommended by the product instructions.

Damp Proofing:

Cementitious parge coatings

“Parging", used primarily on concrete block foundations, is what the process is called when a mason uses to trowel to apply an even coating of cement-like material on the exterior of the foundation walls. In the case of damp proofing, the cementtitious material being used has properties that will help seal the porous concrete blocks and mortar joints. This reduces capillary action and the transference of moisture from outside. Parge coatings can effective damp proofing where there is good soil drainage, but have no crack-spanning ability.

It should be noted that some parge products contain fiberglass, which add overall strength to the foundation.

Asphalt coatings with and without modifiers

Asphalt is a tar-like substance that can be applied to the exterior of the foundation inexpensively by brush, roller or spray. Brushing or rolling requires little skill.

Asphalt damp proofing degrades over time and has no crack-spanning ability. Where codes allow, it can be effective damp proofing where there is good soil drainage.

There are a variety of asphalt products available with additives or modifiers. Modifiers enhance the damp proofing abilities. These products can be troweled, brushed, sprayed, or rolled on. Still these products do not span cracks.

Acrylic and polymer sealers

These are special spray-on sealers are relative easy to apply and can be used on the exterior foundation wall. Often times they are used in conjunction with rubberized asphalt sheeting on exterior walls. required.

Crystallization products

Crystallization products utilize a chemical reaction between the add-mix (product) water, and concrete. The result of this chemical reaction is the formation of growing crystals in the tiny air spaces in the concrete. The reaction is driven by water so the crystals grow denser where they contact moisture. The crystals fill the voids so capillary action cannot take place.

Add-mixes can be sprayed on, troweled on, or mixed right into the concrete. Crystallization products are sometimes used for waterproofing because crystallization can span small cracks.


Rubber polymer-modified asphalt coatings

These waterproof coatings are a step above their asphalt damp proofing cousins. Polymer-modified asphalt is a liquid asphalt coating with rubber polymers. The rubber polymers allow the coating to stretch over shrinkage cracks so water cannot penetrate. These asphalt products do dry over time and their elasticity is reduced meaning; down the road, the coating may not bridge settlement cracks.

These coatings are applied to the outside of the foundation with brush, roller or spray and they dry to form a continuous barrier against water. As with all water proofing coatings, care must be taken to ensure complete coverage of the required thickness.

Overall, these coatings will provide upgraded performance over damp proofing at a reasonable price.

There are many brands and formulations of rubber polymer-modified asphalt waterproofing products. In addition, these products can be used in conjunction exterior drainage mats and panels creating an enhanced waterproofing system.

Compare the Warranties vary widely by product used and system implemented.

Clay-based products

Bentonite, a natural clay material, is an excellent waterproofing material, because it swells 10-15 percent when exposed to water and it becomes impervious to water. The clay is usually sandwiched between two layers of cloth or geotextile and products are available in panels, sheets, and in combination with other urethane, rubber, and asphalt products. Bentonite is a natural and environmentally friendly.

Crystallization products

Crystallization products are waterproofing admixture blends of chemicals, quartz sand and cement. The chemicals contained in the crystalline waterproofing products require the presence of moisture to set off a chemical reaction inside the concrete. The chemical reaction forms complex crystals, which penetrate deep into the capillaries of the concrete stopping the migration of water.

The crystalline process continues as long as moisture is present in the concrete. If no moisture is present, the crystals will lie dormant until moisture reappears and then will reactivate.

In addition to sealing pores in the concrete, the crystals also fill small voids and cracks caused by shrinkage.

The crystallization products can be used in the concrete itself in the case of a poured concrete foundation, or it can be applied as parge coat in the case of a concrete block foundation.

There are a number of manufactures of crystallization products. There are several YouTube videos explaining the process, link to one here

Urethane coatings

These are the most recent introduction among, basement waterproofing coatings. Urethane coatings are considered by some to be the most durable waterproof coatings. These coatings are a derivative of urethane or polyurethane. The synthetic material “urethane” or “polyurethane” (a colorless, odorless, compound) has been formulated into a liquid which can be applied with a brush or roller to form a waterproof foundation membrane. Urethane foundation waterproof coatings have a much longer useful life than the asphalt-based coatings because the coating stays pliable.

Urethane coatings are applied in much the same way as modified asphalt coatings. Depending on the product, protection board may be required to be installed against the urethane coating before backfilling.

Urethane foundation coatings are more expensive than modified asphalt coatings. Some manufactures are mixing asphalt (as filler) with urethane to create a less expensive product with similar characteristics.

Rubber-based coatings

As the name implies, rubber-based coatings are made with rubber. Some are made with rubber polymers additives and some are made predominately with liquid rubber. More rubber is better.

Some of these coatings can be brushed and sprayed on cold and some need to be heated and sprayed by trained professionals. Some will argue that rubber-based foundations coatings are the better than urethane coatings. Usually you will get greater crack spanning with rubber coatings.

Sheet, roll products

Sheet products are manufactured sheets, rolls or panels fastened to the foundation wall. Sheets will usually incorporate one or more of the foundation coating materials listed above.

Sheet products must be lapped adequately at seams, both vertically and horizontally. Fastening methods will vary from self-adhesive to mechanical. Installation usually requires at least two workers.


Since there is a lot of competition among manufacturers of foundation damp proof-waterproof products, do your homework before agreeing to the builder’s standard, or asking for a specific type or brand of waterproofing.

  • Evaluate your needs based on your home site if possible.
  • Check the elasticity or elongation of the product; the higher the elasticity, the better it will span foundation cracks and keep the basement dry.
  • Compare product warranties; not just number of years printed in big bold number, read them to see what is covered and what is not covered.

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