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Tuesday, February 21st, 2012 by Casey Petersen
Moldy Sheetrock and Drywall
Sheetrock is a wonderful product that makes our walls nice and smooth. It replaced plaster and lathe. Sheetrock or Drywall as it is commonly called is made of gypsum and paper. The gypsum is mined and milled into a usable form where it is processed into boards wrapped in paper on both sides.
The paper is the food source for mold growth. Mold is a spore that is everywhere in our environment. When you have a mold spore with a food source such as the paper on sheetrock you have the perfect environment for mold when water is added.
Usually sheetrock is dry with no problems but when water is added to the equation you have a disaster waiting to happen. The sources of water are many, broken pipes, flooding basements, extended high humidity, and direct contact with a damp material such as concrete.
When there is a plumbing leak in a wall cavity there is bulk water forced onto the sheetrock wetting it. When it stays wet, mold grows. When you have a very humid environment it becomes essential that the sheetrock be dried out a sap or mold will develop within a couple of days. In very humid environments sheetrock can start to mold without the introduction of any other water source.
We often find basement walls made of sheetrock where there is mold at the lower level of the walls. When sheetrock is installed we use the term “hang” sheetrock. This assumes that the sheetrock is suspended. Often time’s basements are finished by less experienced people who don’t understand the difference between hanging sheetrock and setting sheetrock. If you set sheetrock on the concrete floor it is not hung or suspended. When this happens you place the sheetrock in direct contact with the concrete that will probably get wet at some time. When sheetrock and concrete come in contact with each other and the concrete is damp, sheetrock acts as a wick. Through the process of capillary action, water wicks up the sheetrock 18 to 24 inches where gravity will stop the wicking action of the water.
Sheetrock and water, whatever the source, is the perfect combination for mold growth. If sheetrock stays dry it is a great material for creating nice wall surfaces. If it gets wet, it is the perfect recipe for mold growth, health issues and reduced property values.
The solution is a good waterproofing system. Bulk water must be kept away from all organic building materials, capillary breaks should be in place where ever needed and dehumidification where high humidity can only be controlled through mechanical means.