Parging Preservation

Q: What’s the best way to fix tiny cracks in the plaster applied on the outside of the concrete block foundation wall of my house?

A: The cement-based plaster applied to block walls is usually called parging, and even though it’s popular here in Canada, it’s also prone to trouble in our climate because of seasonal freezing and thawing action. Water soaks into the masonry during wet times, then expands as it freezes during cold weather, causing damage as it does. This process leads to cracking, flaking and a pretty ugly foundation wall given enough time. The good news is that it doesn’t have to go this way. Hairline cracks are always the first sign of trouble, and these can be filled with a paste made of Portland cement and water rubbed into the affected area. Let this cure for a couple of good days, then apply a soak-in masonry-waterproofing agent. It adds years of life to exterior masonry surfaces because it keeps water out. You could apply a retail-grade water seal product every couple of years, or go with something longer lasting. Industrial formulations can last as long as five years between applications.