Q: What issues should I be concerned about relative to gypsum panel installation during the winter?
A: The biggest issue when installing gypsum panels in winter is the increased potential for cracking. The most common form of cracking occurs at the gypsum panel joint with the joint compound. Cracking in gypsum panels and finished joints only have one source, and that is movement. The challenge often comes when trying to understand why a particular installation cracked, or what caused the movement. Year around, common causes are from changing environmental conditions. Some environmental conditions may be extreme such as seismic events and wind, a once-in-a-lifetime event accommodated by building design. Solar gain can cause tall buildings to move. Seasonal changes also create conditions suitable for movement, and in this case, the effect will be cracking of the gypsum panel.
The issue during seasonal changes is both the change in temperature and humidity. All materials will dimensionally alter as a result of these changes. The amount of the movement will vary with the individual materials. The material property is called thermal and hygrometric coefficients of expansion. Based on the length of the material and the swing in temperature, engineers can predict the anticipated amount of movement by using the appropriate coefficients. For example, a 100-foot-long wall that is clad with gypsum panels and is subjected to a 44oF change in temperature will expand a half-inch. If a comparison is run with common building materials including extruded polystyrene, cement-based panels and plywood, an interesting phenomenon will surface. The plywood, looking only at thermal changes, is the most dimensionally stable. When the analysis is based on humidity, then plywood becomes the least dimensionally stable. Wood-framed walls can be problematic because they will exhibit significant movement while drying out.
As the gypsum panels expand with the differential temperature, stresses are induced within the wall. Joint compounds are cementitious, which means they are good in compression but ineffective in tension. As the stress is increased, cracks may develop where the compound goes into tension and exceeds the material’s capacity. Also, cracks may occur where there is a change in geometry of the gypsum diaphragm. This will occur over door and window openings, where there is a concentration of stress.
The highest probability of cracking as a result of thermal and humidity occurs during and just after construction is completed. That is where the interior environmental conditions experience the greatest change. Changes in seasons, especially going into or out of winter, greatly increase the problem. The industry recommendations for wintertime installation are best stated in the Gypsum Association’s “GA 216-2016 Application and Finishing of Gypsum Panel Products.” Section 4.3.3 states that “where materials are being mixed or used for joint compound the room temperature shall be maintained at not less than 50oF for a period not less than 48 hours before mixing or application and continuing until applied materials are thoroughly dry.” Further in the document, Section 4.3.4 it states that “the room temperature shall be maintained at not less than 40oF for mechanical application of gypsum products and not less than 50oF for adhesive application …”
Wintertime applications require a source of heat. If temporary heat is the only option, it is suggested to refrain from using portable gas or kerosene heaters because they introduce undesirable humidity into the room. If that type of heater is used, GA 216-2016 recommends that a means of removing the humidity be employed.
Gypsum panels and joint compounds experience the greatest extremes in environmental conditions within that first year of installation. The interior space has excess moisture just from the construction process. The drying of concrete, any wet trades and even paints all add moisture to the space. The temperature swing can easily be 50oF from ambient winter conditions, and even more if the HVAC system through its commissioning process is allowed to run at extremely high temperatures.
There are several ways that a contractor can minimize the cracking potential. The first would be to simply understand the increased risk that winter installations incur. The second is to maintain the proper temperature either as indicated in the Gypsum Association document or preferred gypsum vendor documents. If temporary heat is the only option, make sure it is adequate for its intended application. Incorrect type of heat or poorly placed heaters can calcine the gypsum panels with too much heat. Ascertain there is enough air movement within the space to assure proper and even environmental conditions. Protect the completed work from changes in environmental conditions. Damage can occur long after the work is finished if the space is not properly conditioned or maintained. Voice concerns with the general contractor, and document any variances in interior conditions.
Wintertime construction does offer unique challenges, but a little planning, negotiating and documenting can improve the chances for a successful project.
Robert Grupe is AWCI’s director of technical services. Send your questions to [email protected], or call him directly at (703) 538.1611.
