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Embedment depth

Embedment depth is how deep an anchor is set into concrete; the AS 5216 capacity is calculated against it. Short embedment is the main cause of pull-out failure.

By Dan Waring. Last updated 30 May 2026. Verified 29 May 2026.

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Embedment depth is the depth a bolt, anchor, or fastener is set into the concrete or substrate. It is one of the parameters an anchor’s engineered capacity is calculated against under AS 5216: the design assumes the anchor is embedded to a specific depth, and that depth largely determines how much load the anchor carries before it pulls out.

Short embedment is the single most common cause of anchor pull-out failure. Set an anchor shallower than the design depth, because the hole was not drilled deep enough, the slab is thinner than assumed, or rubble in the bottom of the hole stopped the anchor going home, and the rated load no longer applies, even though the anchor is in and torqued. The capacity drops with the depth, often steeply, so a few millimetres short on a structural anchor is not trivial. This is why the engineer’s anchor schedule states the embedment alongside the type, diameter, spacing, and edge distance, and why all of them have to be built as drawn.

Drill the hole to the diameter and depth the manufacturer or engineer specifies, clean the hole out (rubble in the bottom is what robs embedment), and set the anchor home to the marked depth, not just until it feels tight. On a chemical anchor the hole has to be brushed and blown so the resin bonds over the full embedment. If the slab is too thin to take the required embedment, that is a question for the engineer before you drill, not a reason to set it short. See anchors and chemical anchors and tie-down.

Also known as: Embedment, effective embedment, set depth.

Category: Fixings / Anchors.

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Last updated: 2026-05-30. Verified: 2026-05-29. Quarterly review for currency.

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