How large of an overhang can I have on my countertop? - NBC12.com - Richmond, VA News

Silestone® weighs about 15 lbs per sf and may have an unsupported overhang of up to 12 inches. Granite and marble weigh about 18 lbs per sf and may have an unsupported overhang of 10 inches. No unsupported overhangs should ever be placed in such a way that they would be susceptible to tipping if excessive weight were applied to them such as sitting or standing on the edge of a countertop. Care must be taken to insure that the mounting surface is firmly secured to support the weight of the overhang.

- Capitol Granite and Marble