A partially completed masonry wall was left without any covering on the top over the winter. Consequently, the top of the wall was exposed to snow and rain for several months.
What problems can this situation create?
Exposing the top of a brick wall to rain and melting snow allows water to collect in the cores of the brick units, which can cause the upper portion of the wall to become saturated. This exposure is typically much more severe than rainwater penetration through the face of the completed wall.
Saturated masonry can undergo several freeze/thaw cycles during the winter in a northern climate. This action can contribute to premature deterioration of the masonry, especially if the cores of the brick units are filled with water when the wall freezes.
Snow and ice are typically more damaging to masonry construction than rainwater. A portion of the snow or ice melts during the day and refreezes at night, which makes the walls undergo daily freeze/thaw cycles. Repeated wetting of the walls also increases efflorescence concerns.
In regard to the specific wall in the question, deterioration that occurs as a result of multiple freeze/thaw cycles during the limited time frame in which the wall was exposed to moisture during cold temperatures is likely to occur only in the upper portions. Any efflorescence that occurred can be cleaned off the wall.
This limited exposure to severe weathering should not significantly affect the future performance of the wall if it is allowed to dry out, visibly damaged areas are rebuilt, and the wall is properly covered in the future. Minor mortar deterioration is corrected by repointing.
Tops of masonry walls should be covered during winter and summer to prevent excessive water penetration and resulting freeze/thaw or efflorescence problems.