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Moisture and Mold

Water is present during the construction, service life and deconstruction of all buildings. This water may be needed by the building in the form of an additive to a construction material, used by occupants, or the result of weather elements. Moisture problems in buildings stem from leakage in the building envelope, plumbing leaks, excess water and water vapor in the air, freezing of water in materials, the migration of water vapor through materials and systems leading to condensation and wetting of the materials. While all building materials absorb water, each absorbs at different rates and has different capacities. In addition, the absorption of water will affect the physical properties of the materials. 


Measuring the performance of building systems exposed to moisture is difficult. Existing tests examine products under artificially created, static conditions. Building systems experience extremely dynamic conditions where steady-state conditions are rarely achieved.

USG's Position on ASTM C473 and ASTM D3273

In the absence of specific tests for the broad category of construction products, the industry uses ASTM C473 and D3273 for this purpose. ASTM C473 measures water absorption of panels as a percentage of weight. ASTM D3273 measures resistance to mold growth on the surface of interior coatings when exposed to a hot and humid environment. These test results do not represent definitive installed performance in specific project conditions, but do provide indicative measures of performance.

USG is actively working with academic and industry testing leaders to develop a new ASTM test methods specifically for building materials such as wallboard and acoustical ceiling tiles.

Beyond Testing

The key to minimizing mold growth is controlling moisture. Moisture exposure can occur during all phases of the construction process and through the building life cycle from roof, wall and pipe leaks, gross water penetration of the façade, vapor diffusion and condensation, and capillary rise.

Products alone cannot control moisture or prevent mold.

All products become susceptible to mold growth under unfavorable conditions. However, proper management of moisture in the building and selecting products that are appropriate for the application conditions are the building owner’s most effective means of preventing moisture and mold damage.

Systems Approach

Avoiding leaks and preventing excessive accumulation of moisture requires a systems approach to the design and construction of all building elements. USG provides comprehensive information regarding best practices to reduce the risk of moisture damage. USG is the leader in offering products and systems that address the full spectrum of performance needs for specific applications.

USG Testing Services

Learn more about the testing services offered at our Corporate Innovation Center in Libertyville, IL.

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