Detroit Cautionary Tales, Part 2: Coating Does Not Equal Restoring
In this two-part series, I share cautionary tales learned from Cathedral Stone Products founder Dennis Rude, who is one of the nation’s foremost masonry restoration experts.
In Part 1, we discussed the hazards of silicone caulk. Here, we explore the danger of using paint and other liquids to repair cracks.
As I mentioned in Part 1, I recently had the chance to walk through Detroit’s Lower Woodward Avenue Historic District with Dennis Rude. Along the way, Dennis pointed out some significant but common restoration mistakes that put historic buildings at risk of further deterioration. It reminded us both of the importance of education in the field of historic masonry repair.
One big problem, as Dennis explained, is the use of liquid acrylic or latex for repairs.
Waterproof coatings trap moisture, causing further damage.
Using these materials is something we see fairly often. Contractors faced with discolored or damaged masonry cover the area with a waterproof coating, rather than cleaning and preserving it. This thick synthetic material prevents moisture from getting in, and that sounds good. But it also prevents water from getting out—which leads to further damage.
Dennis drew my attention to some intricate stone carvings on a limestone building that had to be at least 100 years old. They were beautifully crafted, and Dennis said the stonecutter who made them had had a lot of skill.
But at this point, the carvings were in rough shape. Someone had attempted to restore the area by filling in the cracks and using caulk, a product that stretches and contracts as a building moves. It’s also waterproof, which, as I mentioned, is a bad idea. It caused the surface to blister and peel, trapping moisture, water vapor, and salts, which continued to damage the substrate underneath.
It’s a shame to see beautiful buildings compromised by a 10-to-20-year fix.
I could see how much it bothered Dennis to see such incredible work being treated so badly, knowing a better solution exists. It bothered me, too. Buildings like this one deserve a generational repair, not a 10-to-20-year “fix.”
That’s why we’re so passionate about education in our field. We want people to know that Cathedral Stone Products were developed as a solution for the problems that are specific to historic masonry preservation. We believe that, when people understand that our formulations are engineered for particular stone types and react the same way as the natural substrate, they can be confident in specifying them for historic masonry projects.
In the case of the limestone carving that Dennis and I examined, I would have recommended the following products:
Our Injection Grout M32. Engineered for historic brick and soft stone, this product is used to fill small cracks and voids (1/16" to 3/8" wide). (We make M31 Injection Grout for concrete and hard stone).
· Our Potassium Silicate Coating. Unlike latex and acrylic coatings, this product forms a molecular bond with the masonry substrate. It’s 92% permeable, allowing salts, water vapor, and liquid water to escape—just like the original substrate.
Another remarkable thing I learned from Dennis: they’ve used similar products in Europe for 160 years. Cathedral Stone Products introduced them in North America relatively recently—another reason for education in our field.
It's always interesting to learn more about what’s possible in the field of historic masonry preservation. As Dennis pointed out—cracks happen and buildings settle—but contractors, architects, and other restoration professionals don’t have to.
