Painting Paperless Dry Wall – A Promising Substrate

Indoor mold and the problems associated with it have been gaining a lot of attention in recent years, especially after the severe hurricanes and floods in the US. Besides being unsightly and causing damage to your property, mold can contribute to poor indoor air quality and potentially lead to health issues such as allergic reactions and other respiratory problems in sensitive individuals.

Mold on Dry Wall

Mold spores are always present in both indoor and outdoor air. Mold only needs a few things to grow and multiply – nutrients (food), suitable places to grow, and moisture. In the past, homes were constructed with conventional materials, such as concrete, brick, stone and hard plaster, that were more resistant to bio-deterioration. Modern buildings contain more biodegradable materials like wallpaper, drywall, wood and wood composites. You can’t avoid the presence of mold spores but you can take steps to control the moisture and food sources that mold needs to grow.

New home, never lived in, extremely poor construction. Pipe broke, water flooded house, not dried within 48 hours.

The newer paperless drywall eliminates the organic food source (paper) by using a fiberglass mat over a moisture resistant gypsum core. This fiberglass mat, however, has a slightly rougher surface than traditional paper faced drywall. After the taping compound is applied and sanded, the contrast between this very smooth, taped surface and the rougher face of the paperless drywall becomes more apparent. Proper selection and application of a primer will eliminate this difference in appearance.

Guidelines for selection and application of primers for paperless drywall.
The Paint Quality Institute investigated characteristics of a primer to deliver a satisfactory finish on paperless drywall. We focused on two main targets:

     a. to deliver uniform finish
     b. to maintain the promise of durability
         (especially water and mold resistance)

Finding a coating to compensate for surface roughness is critical. The figure below shows performance with a low vs. a high volume solids primer. You can see that the high solids primer eliminates surface photographing and results in a more uniform finish. Other key paint ingredients to maximize durability and performance:

    i. Rheology Modifiers – helps to ensure maximum flow and film
       build during application.
    ii. Binder type – 100% Acrylic best to ensure good adhesion and
       water resistance.

Some key specification and observations are captured below:

• The primer needs to be applied at a sufficient dry film thickness to adequately cover the surface and smooth out any imperfections. A high volume solids primer (at least 40%) with good rheology can be applied by roller at a higher film thickness in one coat.

• For adequate coverage, the primer should be applied to a dry film thickness of 1.7 to 1.8 mils dry. The number of coats needed to achieve the dry film thickness will depend on the primer used. The table below lists typical volume solids with the appropriate spread rate needed to achieve those film thicknesses.

• Follow the application instructions of the primer manufacturer stated on the container.

• To maintain moisture control, select a quality, 100% Acrylic primer
with mildewcide protection.

Safety Considerations:

Obtain and read the Material Safety Data Sheet from the manufacturer of the paperless drywall. The paperless drywall has a fiberglass mat on both the front and back sides. Fibers and dust may be released during normal handling and may result in skin, eye and respiratory irritation. Avoid breathing dust and contact with skin and eyes.

Follow these standard work practices:

• Wear loose-fitting, long-sleeved shirt and
   long pants, protective gloves, and eye protection.

• Wear a dust mask when sanding.