February 2010

Moisture in concrete roof decks | Tech Today

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Moisture in concrete roof decks

Concrete's curing and drying rates can affect roof systems

by Mark S. Graham
1 person has posted a comment

Lately, NRCA has experienced an increase in reports of moisture-related problems with low-slope membrane roof systems applied to newly poured, normal-weight or lightweight structural concrete roof decks.

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.

Concrete decks

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 square...

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Comments (1) Login to post a comment or rating

Posted by donscheuerman on 2/2/2010, User rating 
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Not to be dense, but old school was you took a quart of hot asphalt and poured a test spot on the deck at one or more locations. If the asphalt foamed and bubbled and peeled off the deck, the deck was too wet. If the asphalt cooled flat and void free and did not peel off the deck, it was good to go. I guess one of the down sides with single ply and low rise adhesives is old school dosen't work.