Installing Granite With An Overhang
Tom,
We are in the process of replacing our solid surface counter tops with granite. On the breakfast bar the granite will have a 12″ overhang. The granite fabricator recommended that we install corbels for support. What is the best way to install the corbels to ensure that they will support the granite overhang? Is there more than one way to install the corbels?
Thank you,
Carl Wallace
Hello Carl,
I have to make a couple assumptions because you did not provide me with some important information. For the purpose of this reply, I will assume that the granite is 3cm solid stock and the granite color is not in Class D, meaning that it does not have fiberglass mesh on the back to keep give it strength.
Now then, there is some debate about how far 3cm granite should overhang without corbels. If you consider that children might hang or pull on the granite overhang or that someone might sit on it, then you should install corbel at overhangs greater than 10″. If you have Class D granite, install overhangs past 6″. In general, Granite that is solid 3cm stock does not need corbels for flexural strength at 10″. Some granites, like the ones from Saudi Arabia, do not need it at 12″. However, my comments are regarding flexural strength issues and do not apply to safety concerns. Installing corbels is important for the child safely reason mentioned above so if you can live with the knee bangs, then you should install them as follows.
Start 6″ in from the open end, and put one corbel there. Do the same on the other end, unless the counter meets a wall, in which case you should install it against the wall. Then install corbels equally apart between the two outside corbels without exceeding 30″ between any two corbels. For 3cm thick granite at 12″ overhang, I would suggest 6″x6″x 1 1/2″ wood corbels or 6″x6″x 3/4″ steel corbels. Note, you can vary from this advice slightly depending on your exact cabinet dimensions. Just use good common sense.
Best wishes,
Tom Cordova
