Our firm designed an insulated masonry cavity wall system using 4-inch split face concrete masonry veneer with an 8-inch reinforced concrete masonry backup. The veneer wythe contained an integral water repellent admixture in both the concrete units and mortar. The interior wythe was conventional concrete masonry. The masonry contractor constructed these cavity walls in the fall. In February we learned that the tops of the masonry walls were left uncovered throughout the late fall and winter. We are concerned that these walls were damaged by freezing water or that they are storing so much water that it will lead to excessive efflorescence in the spring.
We cannot see any signs of a problem, but how can we determine whether the walls have internal damage as a result of water entering at the tops during construction? Will the saturated masonry walls lead to excessive efflorescence problems? Should we open up the head joints at the top of the wall to create vents in order to help dry out the walls?
Also, the interior surface of the concrete masonry will be painted. How long should we wait before doing that job?
It is unlikely that there will be significant freeze/thaw damage in this relatively short time period. Water absorption of the units is limited by the water repellent admixture in the concrete masonry units. There is visible cracking if water filled the cells of the units and then froze. Water should not collect in the cavity space if the base of the cavity contains proper flashing and weep holes. Presumably, the walls were covered as soon as this problem was discovered. If not, they should be immediately.
I recommend conducting nondestructive tests such as infrared imaging to determine if any water is present in the lower portion of the cells that are not grouted. If water is found, it may be possible to drill holes into the cells at a downward angle through the head joints to drain this water. Extreme care must be taken to avoid damage to the flashing system.
Efflorescence is unlikely because the veneer wythe of concrete masonry units contains an integral water-repellent admixture. I do not recommend installing vents at the top of the wall to help dry it out unless these vents are protected from wind-driven rain.
Merely opening up the head joints at the top of the wall probably makes future problems worse. Without a continuous airflow, it is likely that the additional water entering the wall system through these open joints during rains will be greater than the amount of water that can be dissipated between rains as a result of the addition of these vents.
I do not recommend painting the interior wythe of concrete masonry until the units are thoroughly dried out. There are moisture tests that evaluate when these interior coatings are safe to apply. Consult the paint manufacturer regarding information on tests to evaluate the moisture content of the substrate, as well as the maximum moisture content. Paint applied to wet concrete masonry probably won’t bond properly and peels over time.