Rick my house is 1 year old and I went with granite countertops throughout the house. All are 1.160 to 1.180 inches thick, this granite isn't anything special I selected from the list of builder grade granite and that was the standard thickness. The granite top on my island is 75 inches long and has a 12" over hang along its entire length with nothing under the granite supporting it. Those L brackets don't even touch the granite underneath, purely decorative. Also unless your base cabinets are absolutely flat and level which is unlikely they will shim the granite level which means it probably won't even be resting on the plywood if you extend it out. They shimmed mine and secured it with silicone. In a year of use I have no worry about the granite cracking off with a 12" overhang, 18 inches might make me nervous just from the weight and leverage. With a 12" overhang that's about 1/3 of the total depth which seems a good ratio. I also love this square craftsman edge on the granite, it makes it look even thicker compared to other edging. Note also the Travertine tile backsplash, love the raw stone look of that and used it in the bathrooms as well.
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