What is a Normal Moisture Reading for Drywall?
Following installation, drywall typically attains an equilibrium moisture content (EMC) within a range of 4% to 8%, with a higher EMC in humid environments and a lower EMC in dry climates. A normal moisture reading for drywall is between 5% and 7% under average conditions.
Moisture content in drywall can be measured by:
- Moisture Meter: A handheld device that provides an instant moisture content reading when inserted into the drywall.
- Plastic Sheet Method: Securing a plastic sheet to the drywall surface for 24-48 hours and measuring the weight gained by the plastic, which indicates the amount of moisture absorbed.
If drywall moisture content exceeds 11%, it can lead to issues such as:
- Structural damage
- Mold growth
- Swelling and deformation
- Poor paint adhesion
International and national standards provide guidelines for acceptable moisture levels in drywall. Notable organizations and agencies include:
- American Wood Council (AWC): Recommends drywall EMCs between 5% and 7%.
- International Code Council (ICC): Enforces building codes that limit drywall moisture content to 11% or less.
- ASTM International: Develops standards for drywall moisture content measurements using both the moisture meter and plastic sheet methods.
To ensure drywall performance and longevity, it is crucial to adhere to these regulations and standards by monitoring moisture levels and addressing any excessive moisture promptly.