I am assisting my grandmother in a kitchen remodel. We are building a two-tiered island, the top tier being a bar with seating.

The top piece of granite (3 cm) will be 18 inches, but only hang over about 11.5 inches. The "kitchen designer" at Lowe's recommended 4 corbels to support the 11.5 inch over hang, which is 8 feet in length. The decorative corbels are solid wood, L-shaped,and about 10" x 10", three inches wide.

When the granite people (I should say two young looking adults) came to template/measure for the granite, they said I would need 6 corbels - to reitterate, that would be 6 supports over an 8 ft bar with an 11.5 inch overhang. I find this to be excessive, and if 6 were used, that would be all you see - CORBELS everywhere.

Can anyone assist me in determining how many supports we would need. I would like to go with the original 4, as recommended by the kitchen designer at Lowe's. But then again, I would like to think the granite templaters would know best.

The folks that are installing the stone are the ones with the performance warranty. If you do not do it their way, You could loose your warranty on the product and perhaps hurt someone when the supports pull out of the side of the cabinet and it falls.
My guess is that the supports your using are to light and offer to little strength to hold into the cabinet and the weight of the stone, thus the need for additional supports.
Perhaps a heavier support will allow you to get away from using so many.
The bulk of the granite is being supported by them. The stone is heavy. That is the primary reason for the extra supports. Also do not forget, People place objects and push down on the edge when getting up or being seated. If you were to install larger supports such as ones with longer vertical legs to secure to the side of the cabinet, You perhaps could get away from using so many.
The designer for Lowe's does not understand nor is responsible for the granite top install. If it fails good luck getting them to fix it.

Thank you for your reply.

The supports will actually be attached to a 2x4 framed wall which was built along the back of the cabinet run. The wall is designed to provide the two-tiered look as well as support for the corbels.

I completely understand everything you are saying, and that is why I am confused. We purchased the heaviest corbels we found. They are approx. 4 inches wides, 10 inches deep, and 12 inches in length. That leaves only 1.5 inches of granite not supported by the corbel.

I am still left wondering if the granite company is sacrificing good taste/appearances for an over-assurance on their warranty.

I very much appreciate your suggestions and comments. Have a great day.

I am building almost the exact two tiered island in my kithcen. I was hoping you could help with some of my questions. How did you stablize the 2x4 wall you put along the back of the cabinets. Did you screwed to the floor and to the base cabinets or some other means? How many corbels did you wind up using? Any help with be appreciated.

Hi - I'm apologize for the late reply, but I hope this helps you.

The bar we built actually attached to the kitchen wall on one side. Therefore, I attached the bar support wall to the main wall, to the floor, and I also used small L-brackets to attach it to the back of the cabinets. With the cabinets being attached to each other, the cabinets attached to the floor, and with the support wall, it provided more than adequate support. I also went ahead and went with my gut and used only 4 corbels (instead of the recommend 6 corbels) and everything turned out perfectly - very secure.

Feel free to ask anything else. I would be more than happy to share my experiences.