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Water Repellents


Western US Office
Salt Lake City, Utah
(801) 505-4977

Eastern US Office
Boston, Massachusetts
(781) 488-3088

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Above: Correctly selected and applied water repellents go a long way toward protecting masonry from the damaging effects of water penetration.


Preventing water from penetrating historic masonry is important. If allowed to penetrate, it subjects the masonry to the damaging effects of freeze / thaw cycles as well as the crystallization of expansive salts. Penetrating and breathable water repellents should be considered as a possible tool to prevent water penetration. However, if an inappropriate water repellent is applied, it can actually assist in trapping moisture in the wall instead of keeping it out.


Water repellents are particularly beneficial on horizontal masonry surfaces and could have prevented this damage.


Frequently Asked Questions
about Deteriorated Masonry:

Question: I’ve heard that masonry should not be sealed because the sealers trap water and make the masonry non breathable. Is that true?

Answer: Yes, it is true - if the wrong product is applied..

The wrong ‘sealers’ are those that a) form a film on the masonry, b) adhesively bond to the masonry, and c) are not adequately breathable.

The correct water repellents are those that a) are deep penetrating and do not form a film on the masonry, b) chemically bond to the masonry, and c) are full breathable.

Breathability is the term used to describe a materials ability to freely transfer water vapor.

Question: Will applying a water repellent to my masonry change it’s color?

Answer: It may, depending on the product used and the characteristics of the masonry substrate it is applied to. Prior to applying any water repellent to an entire wall surface, it should be test applied in small inconspicuous areas in order to test the effects it may have on the masonry.

Question: How do I know if I should have a penetrating and breathable water repellent applied to my masonry?

Answer: It depends on:


The over all condition of the masonry wall.


The climate, environment and weather patterns in your area.

3. The results of testing to determine how prone the masonry is to absorb water.

Question: To prevent water from penetrating my masonry wall, can I have a water repellent applied instead of repointing?

Answer: Applying a water repellent should never be a substitute for a quality repointing job. Quality water repellents will not bridge over cracks or voids in the masonry. Making sure there are no cracks or voids in either the masonry units or the mortar is essential. Otherwise, the water repellent may repel water off the face of the masonry wall and direct it into the cracks and/or voids. The water is then subject to the expansive forces of freeze-thaw cycles, and over time deteriorates the masonry units. The water can also contribute to the crystallization of soluble salts. This is known as efflorescence, or if the salts crystallize under the outer surface of the masonry, subflorescence. These too cause the masonry to rapidly deteriorate.

Question: How much does it cost to have penetrating and breathable water repellents applied?

Answer: It depends on:

1. How absorbent the masonry is. The more absorbent the masonry is, the heavier the water repellent should be applied in order to get it to penetrate deeply. Also, the more absorbent the masonry is, the higher the percentage of active solids is required.
2. The results of applying test panels prior to treating the entire wall.

The total square footage of masonry to be treated.

4. How high and accessible the wall is.

Question: How often will my masonry need to be resealed?

Answer: Under normal circumstances, a properly selected and applied water repellent will usually last around 10 years or so. After the water repellent has been applied, it is best to test the masonry to determine how absorbent it has become every other year or so. By keeping accurate records, and comparing the results of the testing to the previous test, one can determine when a water repellent is in need of being reapplied.

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