As the cold winter weather subsides, we are likely to enter a period of wet weather in early spring. Although it is possible to initiate masonry projects at this time, even when the ambient temperature rises above 40 degrees Fahrenheit, the presence of rain should receive special consideration during masonry construction. Unless protected, masonry construction should not continue during heavy rains, as partially set or plastic mortar is susceptible to washout which could result in reduced strength or staining of the wall.
However, after approximately 8 to 24 hours of curing (depending upon environmental conditions), mortar washout is no longer of concern. In fact, the wetting of masonry by rainwater provides beneficial curing conditions for the mortar.
When rain is likely, all construction materials should be covered. Newly constructed masonry should be protected from rain by draping a weather-resistant covering over the assemblage. The cover should extend over all mortar that is susceptible to washout.