Stone Countertop Overhang Support Check
Whether a bar or island overhang needs corbels, by the two rules the stone-industry guidance always states together: the thickness limit (about 6 in at 2 cm, 10 in at 3 cm) AND one-third of the total depth, whichever is smaller. A 12-in overhang on a 36-in top in 3 cm stone fails the thickness rule and needs 5 brackets 8 in deep - two-thirds of the overhang, so the bracket carries the load instead of pivoting on its tip. Weight from the density you enter, not a lookup. Published limits vary by fabricator; theirs governs.
Formula and source
unsupported limit = MIN(thickness rule: 10 in at 3 cm / 6 in at 2 cm, one-third of total depth); slab psf = density x (thickness_cm x 0.393701)/12; cantilevered weight = psf x overhang/12 per lineal ft; if over the limit, brackets = ceil(run/spacing) + 1 at 2/3 x overhang deep.
Stone-industry countertop support guidance, named as GUIDANCE and not a code section; published limits vary between fabricators and stone types.
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