Granite Cracks Explained
We receive several calls per week regarding cracks in the front and/or rear edge of under mount sinks. Occasionally there is a crack by a drop in sink as well but it is rare. It is rare because of the cause.
Under mount sink rails are especially susceptible to these types of cracks because of the break down in the caulk sealant around the sink. As the caulk erodes water enters the space between the wood suptop and the counter causing the steel support rod to rust. A suptop is a 5/8″ – 3/4″ piece of plywood that in installed between the cabinets and the counter to provide structure and support to the counter. Recently, within the last five years, the granite fabrication industry has moved away from steel support rods to fiberglass and other materials, but steel has been the rodding material of choice for twenty years.
How Granite Cracks Happen
One of the biggest geographical differences between the West Coast and the rest of the United States is the thickness of granite counters and the need for support. Still, many granite and quartz counters installed on the West Coast are 2 cm in thickness. The fabricator laminates to pieces together to create a thick edge or bullnose. The sink can be between the suptop and the counter or installed under the counter using a sink setter or straps. It is common for the sink to be sandwiched between the granite and the suptop. Because of this arrangement the intrusion of water is a particular problem. The support rod is usually encased in a polyester rodding glue that breaks down under prolonged contact with moisture. This breakdown along with the absorption of water into the underside of the granite creates all of the conditions necessary for the rod to corrode and begin to expand. The expansion is slow and steady and acts like a spreader pushing the granite apart.
It begins with a small crack usually on the right side of the sink. If you have a crack, look at the inside of your sink rail. You should see a crack or void in your sealant where moisture has been allowed to enter for some time. Unfortunately, your counter has already begun its slow failure. The best thing that can be done now is to reduce or retard the corrosion as much as possible. To do this, remove the caulking, and stop using your sink until the moisture is gone. You can speed the drying by directing a torch or heat gun into the crevice to remove as much of the moisture as possible and reapply a waterproof sealant to the sink. Silicone is recommended. This will not completely remove the danger of corrosion but will slow it down.
If the crack on the sink rail is large enough to see a gap between the pieces, a repair must be performed by an experienced stone restoration professional. The process for this typically includes filling the crack with a flowing epoxy, grinding the surface flat, and filling again with aesthetic adhesive so the appearance blends with the rest of the counter.
Removal of the rod is not always possible
Of course the most permanent solution is to remove the rod. This is much easier to do on the East Coast were 3 cm granite is used without a subtop. When this is the case the sink is installed using straps, sink setters, and other methods. This allows a repair technician to drop the sink and see the rod and in many cases remove the rod without too much effort. A repair of this kind still takes time, but the removal of the rod offers a much better long term value to the customer by saving the counter.
West Coast repairs are limited by the subtop and the severity of the crack. Recently I was called to the project were the client let his counter crack to the point that is was falling apart and rust was being pushed to the surface. In this case I was able to remove the rod and glue the pieces back together.
You can see how corroded the granite rod is and the stain that the oxidation left in the granite. This photo was taken immediately prior to re-installation of a white silicone sealant around the sink.
It still amazes me however when a counter has been allowed to crack to a point almost beyond repair. Further still, these repairs still may not allow for the removal of the rod due to the numerous cracks and the crumbling of the top and the presence of a suptop. Filling the large gap with a flowing epoxy, grinding, the surface, and polishing is an option but as I said, it is not a permanent repair. An example of a repair of this kind is in the video below.
The bad news is that so many counters were installed during the housing boom in most parts of the country using steel for rodding support. I estimate that there are 10,000 rusting rods in the American Southwest alone. My company receives 2-3 calls a day now for these types of repairs and we repair 4-5 per week. We expect this number to double in the coming years.
The good news is that reputable granite fabricators no longer use steel for their rodding support. So you can rest assured that the industry is policing itself. You should ask a lot of questions of your fabricator to make sure you are getting what you pay for. Consider using a member of the Stone Fabricators Alliance and the Marble Institute of America. Both of these organizations hold their members to stringent codes of conduct.
About the author:
Ted is the owner of Sureshine Care and Restoration Services, Inc. in Orange County California with an office in Morgan Hill, California. Ted has been polishing and restoring natural stone and tile since 1987, has written a book on the subject and teaches a four day intensive hands on seminar to teach interested students the stone restoration trade. If you are in need of services in Southern California, please call us at (800)378-0266 or email email@example.com.