Moisture-Related Drywall Losses

Moisture exposure may be caused by water intrusion, such as a leaking pipe; humidity caused by seasonal changes; or any other source that brings unwanted moisture into the home. Exposure can damage a home’s drywall, causing stains, cracking, and mold growth. Each of these conditions has something to tell us about where the water came from, and how long the moisture has been present.

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Drywall is a popular construction material, but when exposed to moisture it can face significant losses.


Staining is an early and noticeable sign of moisture exposure in drywall. Moisture in the air traps dust particles and condenses on cold surfaces, such as the drywall attached to exterior walls, wall studs, and ceiling joists. Drywall will typically contain only a faint discoloration if it is exposed to a one-time event or over a short period of time. However, the longer it is impacted by water, the darker the stain becomes. The stain’s color is an important indicator of the duration of moisture exposure. 

Paper-faced drywall is porous and will likely absorb liquid or vapor water if any is present. Once the drywall dries out, a ring will appear at the edge of the absorption area. The number of rings indicate how many events may have occurred, and the darkness of the rings is a sign of how much water was absorbed each time.

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The dark, concentric stains on this drywall indicate that it has been exposed to moisture on at least two separate occasions.


Drywall’s sensitivity to moisture can also lead to joint cracking. During periods of high humidity, drywall absorbs vapor from the surrounding air and expands. Once the humidity decreases, the drywall dries and shrinks. Drywall expands about half an inch per 100 feet with a relative humidity change from 13 to 90 percent unless control joints are present. Control joints can reduce the potential for cracking due to changes in humidity.

Joint cracking occurs where adjacent drywall panels meet. If such a crack is repaired with tape and finished with a joint compound, it may rupture again if it undergoes further stress. This could be an indication that losses are a result of long-term damage or pre-existing conditions.

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These joint cracks in the drywall show evidence of historical repairs reopening after high seasonal humidity or movement.

Mold Growth

Mold is a general term used to describe one or more of the many hundreds of fungal growths that exist in the environment. Fungi are living organisms and require nutrients, a favorable temperature, and oxygen. Most importantly, moisture is essential for fungal growth. Because buildings and their contents provide food, comfortable temperatures, and air, the availability of water is the key factor in mold growth. Drywall’s paper facing is a particularly good source of food for a colony of fungi, and its surface facilitates the colony’s spread.

While liquid water is necessary for select species of fungi, others can survive in areas with no liquid water present when the relative humidity (RH) is maintained at 65 percent or higher. Typically, fungal spores will germinate, and rapid growth can begin when RH levels are maintained at 80 percent or higher. Once a colony of fungi becomes established, the organisms will survive the lowering of moisture levels by becoming dormant until favorable conditions return. 

If drywall is exposed to moisture due to humidity, water intrusion, or another source, it provides a favorable home for fungal growth, and mold’s ability to return at a later date can compound the losses.

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The extent of mold growth indicate that this drywall has been exposed to moisture over an extended period of time.

Drywall damage can be a serious loss, particularly when mold is given the time it needs to spread. It’s essential to get accurate answers concerning the source and duration of the moisture to determine the next best steps. Donan is an industry leader in forensic engineering, providing sound, documented, and unbiased conclusions. Donan provides relevant information about losses and clear explanations about the perils involved based on close inspection, expert knowledge, and the scientific process. 

Submit a project to see how Donan experts answer questions about the cause of drywall damage or provide other mechanical, electrical, and structural solutions.