Letters: Sticky Situations I

I’m writing regarding an article about adhesives (“Sticky Situations”), written by Jason Nottestad in the September issue. Overall, it was very well-written and very informative. However, there were a couple of items where I felt compelled to comment.
On top of his “concern” list is raised upper bars. He notes that one should use a liberal amount of adhesive and specifically states that said adhesive should “NOT remain flexible after curing.” There are a couple items he failed to mention in covering this subject.
First off, there should never be a piece of stone set that depends on adhesive to hold it in place. Upper bars, if they have an overhang, should have proper support by way of corbels or other suitable structures (angle iron, flat bar, etc.) The prudent rule of thumb is that 3cm material should overhang no more than 10” without support, and 2cm material no more than 6” without support.
More importantly, there should always be twice as much bearing as there is overhanging. This means that an 18” upper bar top can have a 6” overhang as long as it has the other 12” supported. If it’s a 5” pony wall, you’ve got to provide an additional 7” of support to carry an 18” wide piece.
Any upper bar should sit on top of its substrate, with NEVER a chance of it falling off, with or without adhesive to hold it in place.
Secondly, regarding non-flexible adhesives, Jason needs to be sensitive to the audience he’s writing to and be aware that your publication goes to people in very different climates across the country.
I happen to live in a “high desert” environment that is typically very dry. Why is this important? In very dry climates, the most effective way to cool the air is run water over permeable pads that are, in effect, large scale humidifiers. We call them evaporative coolers.
Here’s the problem; during the winter, our average humidity is somewhere between 15 percent to 20 percent. Heated air dries out the inside of the house to below 10-percent humidity. Come April 1, people flip on their evaporative coolers, and the humidity inside their house goes from 10 percent to around 80 percent.
You can only imagine what that does to the dimensional integrity of any wood product. Cabinets grow, substrates grow, wood flooring buckles, stud walls move, floor and ceiling joists creak, etc. If I set countertops in a rigid-setting material, I would have literally hundreds of countertop installations that would have cracked tops due to movement in the substrate. No amount of adhesive, regardless of its strength or liberal use, will ever stop the force of expanding wood.
We use a high quality latex caulk to set our countertops (ALEX 230) and, though we occasionally have to go repair joints that open up, we have never had a countertop crack due to a moving substrate.
One last comment regarding adhesives: It is imperative that only water-based construction adhesives are used around stone. Not all stone will stain with oil-based adhesives; but, when they do stain a piece of stone, it’ll create a replacement situation.
I would lastly like to encourage Jason to continue his work in helping others in our industry and keep writing articles on topics where he has first-hand knowledge. My comments are meant for clarification, not criticism, and I appreciate anyone who is willing to share their knowledge and expertise.

Scott C. Lardner, President
Rocky Mountain Stone Company Inc.
Albuquerque, N.M..