TECHNICAL
BULLETIN 001
Topic
Water Exposure
PUBLICATION
DATE
Fall 2001 |
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The Effect of Water Exposure on Gypsum
Underlayment Floors
LEVELROCK Brand Floor
Underlayments - 2500,3500,4500 and RH (Radiant Heat) are specially formulated
binders that are mixed by USG licensed applicators with sand and water in the
field to pour floor underlayments. The specially formulated binders consist of
gypsum, Portland cement, and other additives. Since gypsum is the primary
component of the binders, it is commonly referred to as "gypsum cement
underlayments".
Pure gypsum casts lose strength and become soft when
exposed to water. But, upon drying, the cast regains 90-95% of its original dry
strength and hardness. Gypsum floor underlayments also exhibit similar
behavior. Gypsum underlayments can be and are being successfully used in areas
that only see occasional water exposure and areas that have a chance to dry out
after such occasional exposures (i.e. the overflow of a bathtub). The product
does not swell or shrink due to this occasional exposure and thus will not
result in cracking or other deterioration of floor coverings used over them.
Furthermore, the higher densities exhibited by LEVELROCK Brand Floor
Underlayments help retard the intrusion of water into the underlayment matrix.
Thus, the occasional water exposure and subsequent drying out of the product
does not cause any long term degradation of strength or stiffness.
However, gypsum floor underlayments are not recommended for use in
areas subject to prolonged exposure to standing water - for instance, in gang
showers, saunas, hot tub decks, swimming pools etc.
If you have
specific questions on the use of LEVELROCK Brand Floor Underlayment products,
please call 1-800-USG-4YOU and we will be glad to help you in deciding if your
application is suitable.
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