Defending homes from damaging moisture and mold

exteriorgypsumsheathing

1. Basement/Laundry Room     2. Bathroom
Mold/Moisture-Resistant Gypsum Panels are an important component in moisture protection.
Physical Description
Mold/Moisture-Resistant Gypsum Panels are typically available in 1/2” (12.7 mm) or 5/8” (15.9 mm) thicknesses, widths of 48” (1.2 m) or 54” (1.4 m) and lengths from 8’ (2.4 m) to 16’ (4.9 m). Conforming to the product standard ASTM C1396, Mold/Moisture-Resistant Gypsum Panels are produced in three variations – a 1/2” standard version, a 1/2” Type C option and a more common fire-resistant 5/8” Type X choice. All these variations are manufactured with a specially formulated core enhanced with additives to help it repel water and discourage microbial growth. The core is wrapped in either treated moisture- and mold-resistant paper facers or fiberglass mats that are naturally resistant to water absorption and mold growth. Edges are generally tapered like most other drywall panels to simplify finishing joints.

Advantages and Benefits
Because moisture damage can start inside wall cavities where it isn’t visible until extensive repairs and remediation are required, Mold/Moisture-Resistant Gypsum Panels are becoming an increasingly common homebuyer expectation. But these products also offer a range of other valuable benefits as well.

o Moisture Protection – It all starts with moisture resistance. Mold/Moisture-Resistant Gypsum Panels repel both liquid and vapor forms of moisture to protect the product itself and the home’s wall and ceiling structures from deterioration. The maximum water absorption value for this product is 5% of board weight. Refer to GA-235 Gypsum Board Typical Mechanical And Physical Properties.

o Mold Resistance – Mold/Moisture-Resistant Gypsum Panels are formulated to resist the development of mold and mildew better than traditional gypsum panel products. Combined with good design, handling, and construction practices, they help provide a pre-emptive strategy against damage to a home’s structure, appearance or performance. Refer to GA-238 Guidelines For Prevention Of Mold Growth On Gypsum Board.

o Fire Resistance – Gypsum drywall products are naturally fire resistant. Mold/Moisture-Resistant Gypsum Panels, specifically the UL-classified Type C or Type X variations, are approved for use in any fire-rated assembly where the corresponding panel type is specified to create a range of fire protection levels, slow flame spread and reduce smoke generation. Refer to GA-600 Fire Resistance and Sound Control Design Manual.

o Construction Efficiency – Fast and easy application and finishing are foundational characteristics of Mold/Moisture-Resistant Gypsum Panels. Their cost efficiency and versatility throughout the construction process help maintain project schedules and budgets for both new construction and remodeling.

o Noise Attenuation – Just as with fire-resistance, it is becoming more and more popular for homebuyers to request their new home provide increased isolation from unwanted noise. Interior walls and ceilings constructed according to assemblies documented in GA-600 Gypsum Fire Resistance and Sound Control Design Manual provide an effective mechanism to achieve improved acoustical performance objectives. Mold/Moisture-Resistant Gypsum Board can be used in any assembly where the corresponding UL-classified 1/2” Type C or 5/8” Type X drywall is approved. more

Limitations
To achieve the performance objectives specified for the walls and ceilings of a single-family residential project, a number of important limitations should be followed to ensure success. These recommendations are intended to provide general information only about considerations that are common in this category of special performance gypsum products:

o Mold/Moisture-Resistant Gypsum Panels are intended for interior use only
o Mold/Moisture-Resistant Gypsum Panels are nonstructural and are not designed to be a fastener base for mounting other materials to walls or ceilings
o avoid exposure to prolonged temperatures exceeding 125°
o wall and floor cavities must be dry before closing-up or applying interior finishes
o not intended for constant exposure to moisture, ponding or cascading water
o to prevent mold and mildew growth, avoid exposure to water during handling, storage and installation and after installation is complete
o not designed to be used as a substrate for tile applications

Refer to GA-216 Application And Finishing Of Gypsum Panel Products.

Products vary by brand. For more specific limitations related to the gypsum panel being considered, consult with the product’s manufacturer.

Frequently Asked Questions
Below are answers to typical questions our technical experts address on a routine basis. These answers may provide additional information you are seeking as well. To submit an inquiry of your own, click here.

1. I understand that even Mold/Moisture-Resistant Gypsum Panels should not be used in so-called “wet areas.” Can you explain where this product can and cannot be used?

Mold/Moisture-Resistant Gypsum Panels are excellent for use in high humidity areas and even where an occasional splash of water is expected. Appropriate areas include powder rooms, adjacent to showers or tubs, behind counter areas/base cabinetry where plumbing fixtures are located, and in laundry rooms, mud rooms, etc. However, neither the model codes nor the Tile Council of North America’s (TCNA) Handbook allows for the use of these boards behind the tile in the shower or tub area or as a base under the pan or around a swimming pool or sauna. For acceptable materials in wet areas, consult the local code or the TCNA.

2. Are any special precautions recommended when moisture/mold resistant board is applied as a finished wall surface in below grade basements?

Yes, care must be taken to ensure that no moisture migrates through the walls. Refer to GA-216 for installation recommendations.

3. Are any special precautions recommended when moisture/mild resistant board is applied to unheated HVAC, mechanical or storage areas?

Yes, unconditioned spaces can experience great swings in temperature leading to condensation. Refer to GA-216 and consult with your preferred supplier for product recommendations.

For Further Information
To read more about the testing procedures to evaluate the moisture-resistant characteristics of the core and facers of a gypsum panel product, refer to ASTM C473.

To read more about the testing procedures to evaluate the mold-resistant properties of the core and facers of a gypsum panel product, refer to ASTM D6329.