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December 24, 2012 - January 6, 2013

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 Tim Davis of Glidden Professional on January 2, 2013:
     I would agree with Channing on the need for additional information, prior to drawing a conclusion. In addition to his points, the investigation should also look at the interior operations of the building. Is there is a source of humidity that could be drawn into the CMU walls such as heaters, operations within the building, etc. If so,  then there may be a vapor drive occurring. Even if the walls are sealed, the vapor could be condensing at or above the roof deck and be carried back to the walls. The moral of the story would be that if the moisture source is not obvious, then the investigation becomes very complex. A dew point anaylsis of the facility may indicate that water vapor is condensing within the wall cavity and causing the issue. Combining a dew-point analysis with an air infiltration/exfiltration survey may prove beneficial to the investigation. It may be surprising to some, to find that the insulation and air sealing techniques can contribute to moisture issues

From Channing Lewis of ROMA - Eco Sustainable Building Technologies on January 1, 2013:
     For starters, it would help to provide more information about this particular CMU wall...is it freestanding and above grade, or is it backfilled on the exterior side or open to the air? Also, is the repeated failure in the same area or widespread across the entire surface? Look for discoloration (typically lighter in color, sometimes chalky).
      If the CMU wall is older than 5 years, have the joints shown any sign of cracking or any signs of organic growth? This is a sure sign of water intrusion. Is the failure isolated to the bottom or top of the vertical wall? "Bubbling" of elastomeric coatings is often due to moisture intrusion as well. If this is a covered structure, and CMU is contiguous to the roof, you may want to start at the top and work down performing a leak test. There are multiple tpes of CMU "block filler/primers" that will help, but if there is not a moisture/vapor barrier on the exterior side, they will ultimate fail and the water will eventually find daylight at the weakest point of exit, following gravity.

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Tagged categories: Building Envelope; Coating failure; Concrete masonry units (CMU); Humidity and moisture


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