It’s always interesting to write a column two months in advance of when it actually hits the street. As this column is being composed, it’s about 25 degrees Fahrenheit outside in the Washington D.C. suburbs, and the snow that fell six days ago is a frozen mass. Not much liquid moisture outside for the past two weeks. It’s been cold.

But seasons come and go and spring arrives eventually, and when it does arrive, it typically brings rain and floodwater. And when that occurs, the phone lines at the Gypsum Association start to light up with inquiries about remediation of water-damaged gypsum board.

Traditional gypsum board products do not like water. Some of the new panels and boards are designed to function better in a moist or wet environment; however, the regular wallboard that is the most familiar to applicators must be kept dry.

GA-216, “Application and Finishing of Gypsum Panels Products,” is very clear when it addresses water or moisture and its relationship to gypsum board: “(g)ypsum panel products shall not be used where there will be direct exposure to water or continuous high humidity conditions.” If it is a wet installation area, don’t use gypsum board.

Gypsum board also must be kept dry to prevent the growth of mold. Again, newer products have come onto the market in the past few years that exhibit an increased ability to resist the growth of mold; however, the regular wallboard that has been sold for decades does not have the same characteristics and it must be protected before and after installation.

WHAT HAPPENS WHEN WET?

So what to do if installed board gets wet? The springtime questions arrive like a flock of swallows beginning in late March every year and run until early summer. And they generally involve two circumstances.

The first circumstance is a flood or an overpowering rain event that saturates installed or stored board. Part of a house has been flooded and the resident or owner wants to know if the board can be saved. “It looks clean” is the common statement, “so can I use it?”

The simple and best answer is an emphatic “no.” Gypsum board that has been exposed to flood water likely has been polluted by the dirt and contaminates carried by the water and the risk that the board may be contaminated greatly outweighs the benefits of keeping it in place. In addition, the metal fasteners used to attach the board to the framing members were almost certainly exposed to water. If some of the rust-inhibiting coating was knocked off during installation, they will rust when re-painted.

The second scenario involves pipes that burst when they froze over the winter and leaked water when they thawed in the spring. The water from the pipes has saturated a ceiling and the occupants want to know if they can keep the board in place.

In this case, and in similar instances, the answer often is yes, you can keep the installed board and re-use it; however, you do have to meet certain conditions. You need to:

Know the source of the water. Don’t guess. If you can’t specifically identify the source, remove and replace the board.

Be certain the water was not contaminated. If it was a clean water intake pipe that burst and dripped onto the ceiling, you probably are OK. If it was a waste clean-out line, you have a problem and need to replace the board.

Determine that the board was allowed to completely dry and that no evidence of mold growth exists.

Make sure that the board is structurally sound and there is no evidence of rusting fasteners or physical damage. Wet board-and especially board that has been wetted repeatedly-can begin to slump and sag, especially at areas adjacent to fasteners. While an adept finisher can cure some ills, it often is preferable (and more cost effective) to simply remove and replace any board that appears physically questionable.

In addition, if the board was installed as part of a fire-rated system, the replacement pieces need to be installed consistent with the rated system design. Remember, this also includes installing the proper fasteners on a correct spacing pattern and staggering the joints between individual gypsum panels correctly.

MOISTURE METERS

Another yearly phenomenon can best be described as the “migration of the moisture meters”-an annual springtime occurrence that arrives simultaneous with the floods. Every spring questions abound about the use of moisture meters with gypsum board and the reliability of the readings obtained.

Using a moisture meter with gypsum board is a challenge because the physical moisture content of gypsum board is quite low. Consequently, the moisture content in the core of the gypsum board fluctuates as it attempts to maintain equilibrium with its surrounding environment.

This is not to say that moisture meters are not a useful tool when used with gypsum board. What it is saying is that hand-held moisture meters work best with gypsum board when they are used to provide relative or rank-order readings of moisture content between gypsum boards in different areas of a building. You can use them to determine areas, or boards, that are relatively “wet” or “dry” but caution should be exercised when attempting to determine specifically “how much wetter or dryer” two separate areas or boards are. Relative readings may not reflect the actual moisture content of the gypsum board core and the surface paper in the test areas.

And like all equipment, using a moisture meter takes some practice and experience. They are best used by properly trained professionals who know how to correctly calibrate the meter for the specific material being measured. It stands to reason that a meter calibrated for wood is unlikely to provide accurate readings for gypsum.

Gypsum board is intentionally exposed to moisture on occasion, in particular when it is treated with a textured spray material. Popcorn and similar textured ceilings are commonly used to decorate residences and the process of texturing the ceiling introduces moisture-laden texture onto gypsum board.

Accomplished correctly, the introduction of the moisture inherent in the texture is not problematic for the gypsum board substrate. Care must be taken to install the board in accordance with specific installation requirements intended to mitigate the negative impact of the wet texture on the board (primarily restrictions on board installation orientation, board thickness, and framing spacing), and the texture must be installed in accordance with manufacturer’s instructions. But the system performs quite well and has for many years.

The basic rule with water soaked or water damaged gypsum board is remove or replace it if you don’t know the source of the water. In some instances, however, wet board can be salvaged and re-used. Hopefully, Mother Nature will cooperate this spring. W&C