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Structural

Cantilever

In Plain English

A beam or slab that sticks out from a wall or support with no column at the free end.

Definition

A structural member that projects beyond its support and is anchored only at one end. Cantilevers rely on bending resistance at the fixed support to carry loads applied along the projecting portion. They are commonly used for balconies, overhanging roofs, and bridge decks.

Why It Matters in Bidding

Cantilevered elements concentrate bending stress at the support, so they drive structural costs through heavier reinforcement, deeper members, and tighter shoring and formwork sequencing that estimators must price beyond simple square-footage takeoffs. Misreading a cantilever on the structural drawings can leave a bid short on rebar, embeds, and temporary support, eroding margin or triggering change orders after award.

Example

An estimator pricing a 6-foot cantilevered concrete balcony adds extra top reinforcement, additional shoring duration, and a longer formwork cycle to the takeoff rather than using the typical slab unit rate.

Related Terms

BeamMoment ConnectionDead LoadLive Load

Frequently Asked Questions

The fixed end must resist all bending and shear with no help from a far support, so designs call for heavier reinforcement, deeper sections, and stiffer connections. Construction also requires shoring to stay in place longer until the member gains strength, adding labor, equipment, and schedule cost the estimator must capture.
Verify the projection length, the reinforcement schedule at the support, any embedded plates or post-tensioning, and deflection or camber notes. Coordinate the shoring duration and reshoring requirements with the schedule, and confirm whether the structural engineer requires special inspection, since these items are frequently underpriced when treated as ordinary spans.
Yes. Cantilevers often blur the line between concrete, steel, and formwork scopes, especially around embeds, waterproofing at balconies, and connection details. Clearly assign these items in scope sheets and exclusions so no sub double-counts or omits them, preventing gaps that surface as change orders after the project is awarded.

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