Countertop overhang support — the seated cantilever limit and when a bracket is required

A seated overhang has a hard unsupported limit: ~6″ at 2 cm, ~10″ at 3 cm (NSI). Go past it and the stone cracks at the cabinet line — a deeper seating overhang needs a corbel or hidden steel bracket. A standard front overhang is only ~1¼″, so it never needs support.

A side cross-section through a kitchen island comparing two seated overhangs. On the left, a 15-inch seated overhang with nothing supporting it cracks at the root where the slab passes the cabinet, because unsupported stone can only cantilever about 6 inches at 2 centimeters thickness or 10 inches at 3 centimeters per Natural Stone Institute guidance. On the right, the same 15-inch overhang is carried by a corbel or a hidden steel bracket and is safe. A standard non-seating front overhang is only about 1.25 inches, well within the limit. — Source: seatingOverhang cantilever check (6″/10″ by thickness) from the countertop calculator; NSI

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A side cross-section through a kitchen island comparing two seated overhangs. On the left, a 15-inch seated overhang with nothing supporting it cracks at the root where the slab passes the cabinet, because unsupported stone can only cantilever about 6 inches at 2 centimeters thickness or 10 inches at 3 centimeters per Natural Stone Institute guidance. On the right, the same 15-inch overhang is carried by a corbel or a hidden steel bracket and is safe. A standard non-seating front overhang is only about 1.25 inches, well within the limit.

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    <img src="https://remodelcalculators.com/api/figure-embed/countertop-overhang-support" alt="A side cross-section through a kitchen island comparing two seated overhangs. On the left, a 15-inch seated overhang with nothing supporting it cracks at the root where the slab passes the cabinet, because unsupported stone can only cantilever about 6 inches at 2 centimeters thickness or 10 inches at 3 centimeters per Natural Stone Institute guidance. On the right, the same 15-inch overhang is carried by a corbel or a hidden steel bracket and is safe. A standard non-seating front overhang is only about 1.25 inches, well within the limit." width="800" height="500" style="width:100%;height:auto;border:0" loading="lazy">
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    Diagram: <a href="https://remodelcalculators.com/construction-diagrams/countertop-overhang-support" target="_blank" rel="noopener">Countertop overhang support — the seated cantilever limit and when a bracket is required</a> — courtesy of <a href="https://remodelcalculators.com" target="_blank" rel="noopener">RemodelCalculators.com</a>
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