Finishing Gypsum Panels in Cold, Humid, or Critical Light Conditions

USG boasts an outstanding portfolio of innovative finishing solutions for drywall panels. Although a great finish is possible when you partner with USG, certain installation conditions outside of your control must be addressed with the correct approach to ensure a perfect finish.

Finishing panels in areas with critical light or ones with humid or cold conditions present challenges to the drywall construction trade that can ultimately affect the finished product. The following industry best practices can help improve finishing success on projects featuring these less-than-ideal conditions. Perhaps just as importantly, these practices can also help manage expectations of owners, builders, and design professionals, which reduces the possibility of callbacks that delay building schedules and hurt the bottom line.

Cold Conditions

Joint compounds perform best at temperatures and humidity that are also comfortable for people—anything too hot or too cold will affect the product’s application and drying time. Applying finishes in cold temperatures and high humidity can cause product failure that may result in time-consuming and expensive repairs.

Ideally, all joint compounds should be used at a temperature of 55 °F or higher, otherwise drying times are lengthened and bonding capabilities are reduced. Job delays, joint cracking, and delamination are just a few of the side effects of finishing joint compound in cold conditions.

Raising temperatures to acceptable installation levels can be best accomplished through the existing heating sources of a building. Temporary heaters may seem to be the best solution, but they are prone to producing fumes that can stain the surfaces of building materials. These types of heaters can also add water vapor to the air, which both slows drying times and creates uneven heat throughout the building.

Humid Conditions

Just as the temperature of an environment can affect joint compound, so too can its levels of humidity. It’s important to be aware and in control of the relative humidity (RH) on the jobsite because the drying time of finishing and decorating materials is lengthened whenever the environment has high relative humidity. To further complicate things, joint compound releases moisture into the environment as it dries, which only adds to the existing humidity that lengthens drying times.

The process of reducing relative humidity requires raising the temperature with proper ventilation to ensure that moisture can exit the building. The following chart shows how drying times for joint compound will vary within a 24- or 48-hour period depending on the temperature and relative humidity of the environment:

As a general rule, raising the temperature by 5 °F will lower relative humidity by 15%. For example, when the relative humidity is 65% at 55 °F, raising the temperature to 60 °F will lower the relative humidity to 50%. For ideal results, adequate ventilation is required to ensure that water will evaporate from the joint compound and escape the building. When corner angles dry at the same rate as the other taped and finished joints, the ventilation can then be considered adequate.

Critical Light Conditions

With the advent of building designs that allow natural light into living and work areas, such as skylights or glass curtain walls, drywall professionals were met with new challenges to accommodate the effect of critical light on finished gypsum panels.

Finished drywall is never an even surface because joints and fasteners must be concealed with coats of joint compound. Because of this, it’s impossible to achieve a truly flat surface, so panels are usually finished with an arching method to prevent any recesses or ridges that cast distinct shadows in critical light.

Under critical light conditions, gypsum panel surfaces require special treatment to ensure attractive, blemish-free surfaces. Acute attention to these potential lighting problems is of the utmost importance to ensure satisfactory results for owners, builders, and design professionals alike.

The placement of panels in regard to the direction of light is important in reducing the effects of critical light. Ideal installations will feature panel joints running parallel with the direction of the light, but larger walls may be exposed to more than just one light source. These conditions result in shadows that can only be prevented by special finishing of the entire wall and ceiling surfaces.

The USG Solution

Find success in USG’s range of performance-based finishing solutions. Additional application tips and resources on the USG Interior Panel and Finishing Solutions portfolio can be found here.