Detroit Cautionary Tales, Part 1: Silicone Caulk is the Wrong Patch
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 the field of masonry restoration, we often encounter inadequate repairs and questionable craftsmanship and product decisions. Silicone caulk is the most common and the most damaging of these choices.
On a recent business trip to Detroit with Dennis Rude, I saw structure after structure with caulk repairs. As we walked along Woodward Avenue, a renowned street lined with museums, theaters, and other grand buildings, Dennis pointed out instances where caulk was used to repair stone.
Caulk is often used to repair stone, but it causes damage.
For example, a beautifully executed terra cotta feature had, unfortunately, been patched with caulk. Dennis reminded me that caulk is simply not compatible with masonry—although it does prevent water from penetrating, it fails to allow moisture and salt to escape. That means cracks will continue to spread, further damaging the substrate. Later repairs with caulk will only exacerbate the problem.
When it comes to repairing any masonry substrate, caulk is rarely the correct product. What you want is compatibility with the masonry. You want to use a product that mimics the masonry’s own breathability—allowing water and salt to pass through as it would normally.
To make the specific terra cotta repair we saw, I would have suggested:
Our Jahn M100 Mortar. M100 is specifically engineered for compatibility with oven-fired materials and will achieve a permanent repair that both enhances and protects the original substrate.
Stainless steel rods or mesh to reduce movement—always stainless steel!
Our M32 Injection Grout, engineered for cracks 1/16" to 3/8” wide.
Our Terra Cotta Coating Glaze, which forms a molecular bond to protect the patch while replicating the original finish.
As Dennis pointed out, the best repair is one nobody notices, lasts as close to forever as possible, and one that will do no further damage to the original structure.
In part 2 of this series, I’ll share another cautionary tale from my Detroit walkabout with Dennis Rude.
