It has been several months since my last article on stress and countertop failures appeared. Since that time, I’ll bet your personal stress levels have risen a bit due to a struggling economy. I am hoping everybody is managing well and not letting a season of bad economy stress you out.
In life and in fabrication, it is impossible to get rid of all stresses. But we can manage it and reduce the risk of failure. Part I in this series on solid surface failures explained how stress moves across a counter, specifically the front edge of a counter. I explained the two types of stresses that cause countertop failures: compression of molecules (at the top edge of the counter) and expansion of molecules (along the bottom edge of the counter).
We know it is impossible to get rid of all the stress in life and likewise all of the stresses in our countertops. An inside corner is a magnet for stress, and proper fabrication is important in managing that stress. An inside corner traps stress, and the stress must travel around the radius to dissipate. Think of stress as energy looking for relief. The failure is the inability to release that energy. Your goal as a fabricator is to help the energy building up in the corner to move throughout the top, relieving the trapped energy.
Corner cabinet construction and home-owner usage are beyond our control as fabricators. This is why we need to ensure our method of fabricating countertops will withstand multiple construction variables. Many inside corner cracks can be found over a Lazy Susan cabinet. By construction, some Lazy Susan cabinets have no support on the inside corner. Without support, the chance of bowing, sagging or being physically pushed down is greatly increased.
The next two culprits for failure are heat from electric crock pots or skillets and weight from something — or someone — on the counter. Heat will cause the counter to expand, revealing stress from heat traveling into cooler areas of the countertop. Heat, causing expansion, and cold, causing contraction, are working against each other and square inside corners do not release stress effectively, leaving the stress concentrated at the corner instead of moving through or across it.
In our company, we tell customers to put crock pots and other hot items on trivets. We also provide customers with at least two solid surface cutting boards for every kitchen installed. When it comes to weight, I recently identified that a consumer was allowing his children to climb on top of a counter to get glasses from a cabinet located over an inside corner with a Lazy Susan cabinet. I advised him as his young children are growing they are gaining weight and the countertop will eventually fail. Here we have energy combined with a lack of support coming together and causing a failure.
The goal during fabrication is to eliminate trapped energy in corners as much as possible. You want that energy to move around the corner. Manufacturers have focused a lot of their fabrication manuals on how to fabricate an inside corner. When you look at these manuals, think of how the manufacturer uses fabrication techniques to keep the energy of stress moving around the corner. As a repair agent, one of the first questions I have to address while doing a repair is: Where did the stress come from that caused the failure and how do I best eliminate it? I also have to design the repair to hold up to stress.
Several things jump to mind that are important in keeping the stress or energy moving. One is the larger the inside radius, the easier it is for energy to move around the corner because there is more surface for the energy to move across. Tighter radii cause the energy to be more concentrated. (See Figure 1.) Corner blocks also allow energy to continue moving.
Remember, stress is looking for the weakest spot to release its energy. Glue joints are the perfect spot for that to happen. I have found many inside corner cracks that have originated where corner blocks and buildup are seamed together with the seam too close to the inside corner. Most manufacturers call for such a seam to be at least 2 in. from the corner. Two inches is the minimum, the further that joint is from the corner the better.