Acceptable Moisture Content
The moisture content of various paintable substrates is given as a percentage when using any of the different types of moisture meters. The following are generally accepted percentages of moisture content by The Master Painters Institute:
Concrete: Moisture content should be under 12% for coatings work to proceed. Excess
moisture can lead to issues associated with high alkalinity and efflorescence, as well as
adhesion issues and delamination.
Clay and Concrete Masonry Units: Surfaces should contain no more than 12% moisture before paint application. As with concrete, issues related with high alkalinity and efflorescence can arise. The entrapment of moisture by the paint film can potentially affect the curing, adhesion, and the overall integrity of the paint film.
Wood: Interior wood should contain no more than 12% moisture prior to painting. Exterior wood may be allowed to contain no more than 15% moisture. When it comes to wood furniture or cabinetry, the moisture content must be as low as 6%. Painting over wood with excessively high moisture content can result in loss of adhesion, blistering, peeling, cracking, and discoloration.
Dressed Lumber, Wood Paneling/Casework: The moisture content shall not exceed 12% for interior applications, and 15% for exterior applications.
Drywall: As drywall is very sensitive to moisture, drywall can be considered “moisture-
compromised” when the % moisture content exceeds 1%. Excessive moisture in the drywall can lead to discoloration of the coating, as well as growth of mold or mildew.
Plaster: Moisture readings must be taken to assure that no more than 12% moisture
content is in the plaster prior to the application of any coating.
Stucco: An acceptable moisture content for stucco is 12% or less. Elevated moisture can lead to discoloration of the coating, as well as delamination and loss of adhesion.