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Edge distance

Edge distance is how far an anchor sits from the concrete edge, a key input to AS 5216 capacity. Too close and the concrete breakout cone fails early.

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

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Edge distance is the distance from an anchor to the nearest edge of the concrete member it is fixed into. Along with embedment depth and spacing, it is one of the key inputs to the anchor’s capacity under AS 5216: an anchor too close to an edge has less concrete around it to resist the load, so it fails earlier.

The mechanism is the concrete breakout cone. When a loaded anchor tries to pull out, it drags a cone of concrete with it; near an edge that cone runs out of concrete and breaks away early, so the anchor pulls free at a fraction of its rated load. Set a mechanical anchor too close to an edge or corner (as a guide, less than about 50 to 100 mm depending on the anchor diameter and embedment) and over-torquing it can snap a cone of concrete straight off the edge at install, before it has even seen its design load. Radial cracks at the surface around an anchor are the warning sign of insufficient edge distance or over-torque.

The engineer’s anchor schedule states the minimum edge distance alongside the type, diameter, embedment, and spacing, and all of them have to be met together. Before drilling, check the minimum edge distance in the manufacturer’s data or the engineer’s detail, and stand clear when applying final torque to an anchor within 100 mm of an edge. If the fixture has to sit close to an edge, that is a design question (a chemical anchor, a larger member, or a different detail), not something to fudge on site. See anchors and chemical anchors.

Also known as: Edge spacing, distance to edge.

Category: Fixings / Anchors.

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References

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

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