Moisture In Concrete Roof Decks

Lightweight structural concrete roof decks include the following.

Moisture in concrete roof decks.

The presence of moisture can result in deteriora tion of moisture sensitive roofing materials and adhesive bond. Excessive moisture from a concrete deck can be pressure differential driven into and condensed within a roof system. This paper summarizes some of the challenges associated. The maximum 75 percent rh value lower for some roofing material types has proved to be a successful threshold for assessing a structural concrete deck s dryness.

In recent years the roofing industry has become increasingly aware of the problems caused by moisture in concrete roof decks that migrates into the roofing system. Also published in rci interface april 2014 abstract. Moisture in new concrete roof decks. Edge of the concrete s cure and moisture release rates.

They suggest decks receiving rooing. The moisture can accumulate in the layers under the roof membrane and cause deterioration and loss of strength of cover boards and facers on insulation boards. In our research dupuis and i conducted limited astm f2170 testing and found mean relative humidity values from 89 to 99 percent in existing concrete roof decks cov ered with membrane roof systems that range from 4 to 7 years old. The nrca also recommends that lwsc not be used for roof decks or toppings for roof decks.

If there is no vapor retarder on the concrete roof deck moisture from concrete can migrate into the roofing system over time and cause significant damage. Now introduce moisture from roof leaks to the ferrous metal and the result is rust. The problem in recent years the roofing industry has become increasingly aware of the problems caused by moisture in concrete decks that can migrate into the roofing system. Currently acceptable roof system specific relative humidity values for concrete roof decks do not exist.

This newly released 272 page research report addressesmoisture release on structural concrete roof decks. Active roof leaks can lead to roof deck deterioration over time leading to failures all of these locations have a higher likeliness for premature corrosion. They suggest that if lwsc is used that designers specify the concrete s drying parameters using astm f2170 to determine the relative humidity rh. Installing a vapor retarder over the concrete deck is the primary method of addressing this problem.

Funded by a group of north american roofing industryorganizations including the roofing alliance and nrca sri consultants inc middleton wis performed fundamental research and. Our moisture analysis demonstrates much of this water will remain in the concrete deck following roof system installation.