Mold growth is a major problem for house owners, as it often occurs on the surface of building materials in damp houses. The principal method to control mold growth on building materials is to prevent water penetration into the materials. A study was recently conducted to determine water absorption rates of different wood species and panel materials used as building materials, when water intrusion occurs. The results showed that solid wood absorbed the least quantity of water among the building materials tested. Upon exposure to water for 7 days, the moisture content (MC) of solid jack pine, black spruce and balsam fir were found to be less than 24% when exposed on one side of the lumber and less than 57% MC when exposed on all sides. Among the three wood panels tested, medium density fiberboard (MDF) and oriented strand board (OSB) had higher water absorption rates, over 70% MC when exposed to water on one side of the panel and over 100% when exposed on all sides. The water absorption rate of plywood lay between that of solid wood and composite panels. Samples of other materials tested, such as gypsum board, fiberglass and ceiling tile, almost reached their saturation point in 1 hour upon water intrusion on all sides of the materials. Most panel samples exposed to water on one side were affected by mold in 7 days; on the other hand, the samples exposed to water on all sides were not affected by mold, because of their very high moisture content.

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