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October 14 - October 18, 2019

How can it be determined if moisture within a CMU wall is causing repeated coating failure? If so, can the source of moisture entry be accurately identified for correction?

Selected Answers

From Zenith Czora of Parex Davco on October 17, 2019:
Moisture presence can be detected by the dampness and dark spots on the CMU wall .With a reliable moisture meter for concrete, the reading should not exceed 5%. If it is exceeded, then there is a problem. Any presence of moisture within the CMU also drives the soluble salts out to the surface, forming efflorescence that will cause adhesion failure, resulting in blistering and, worse, film delamination. Using a breathable/ permeable coating that will allow the moisture to escape but not let bulk liquid get in through could resolve the issue if the moisture source is from the room passing through the wall.The source of moisture may come from different directions. First, you need to investigate whether the moisture is being driven by air from inside to outside, if there is any leakage on the roof that went into the cavities of the wall, if moisture is coming from the ground due to inefficient damp courses or is it caused by wind-driven rain. If there is any leakage, it needs to be fixed; otherwise, there will be recurrence of the problem.

From Michael Halliwell of Thurber Engineering Ltd. on October 15, 2019:
I can't help a lot on the coatings failure side, though I would suspect excess moisture, especially during application and curing, would play an appreciable role in coatings failures on CMU walls. On the source side, that can be quite difficult. Concrete is a porous medium and moisture can make its way though almost anywhere. With CMU walls, it could be anything from a poor roof seal, condensation on a ceiling vapor barrier, a penetration that wasn't sealed correctly, poor drainage causing water contact with the wall...all sorts of sources. If the failure is in one area, you'll likely have a specific issue that may be easier to pin down, but if it impacts a large area, a broad source for the moisture can be a lot harder to find.

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Tagged categories: Asia Pacific; Concrete masonry units (CMU); EMEA (Europe, Middle East and Africa); Latin America; Maintenance + Renovation; North America

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