In the reported instances, significant amounts of water have
been found within roof systems within several months to up to three
years after construction. In most of the situations reported, it
was determined the roof membrane was watertight and not the source
of moisture infiltration. Nevertheless, NRCA has some recommendations for
avoiding such problems.
When mixed, poured and formed, normal-weight and lightweight
structural concrete contain significant amounts of water. As
concrete cures and hardens, it consumes large amounts of this water
through hydration and evaporation. For example, a 4-inch-thick
concrete slab will release about 1 quart of water for each
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