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Construction glossary · Steel and structural

What is camber in a steel beam?

Camber is an upward curvature fabricated into a steel beam so that it deflects down to flat once the dead load of the deck and wet concrete is applied. Framing plans call it out per beam, typically as a note like C = 3/4 in on longer composite floor beams. For estimators it is not a quantity to measure but a per-beam fabrication cost adder, and getting it wrong shows up later as extra concrete in the slab.

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Updated August 2026 · Reviewed by the Ruh construction team

Built-in upward curveOffsets dead-load deflectionSpecified in inches at mid-span
The definition

Camber, explained.

Camber is intentional upward curvature rolled or heat-set into a steel beam at the fabrication shop so the beam comes down flat under the weight of the deck and wet concrete. On US commercial jobs it appears on the structural framing plans as a per-beam callout, usually a note like C = 3/4 in or C = 1 in next to the beam size, most often on longer composite floor beams where dead load deflection would otherwise leave a sag in the floor. The fabricator sets the camber, the erector places the beam camber up, and the concrete crew depends on the beam settling flat so the slab pours at a uniform thickness. New estimators make two predictable mistakes with camber: they treat it as something to measure when it is really a count of cambered beams carried as a fabrication adder, and they skip the framing plan callouts entirely, which leaves the steel quote light and hides the concrete overrun risk if beams arrive uncambered or over-cambered.

How it is measured

Camber is taken off as a count, each, of the beams flagged with a camber callout, grouped by camber dimension if the fabricator prices tiers differently. The callouts live on the structural framing plans, with the general notes or beam schedule sometimes setting the minimum camber the shop will fabricate. Camber adds nothing to steel tonnage; the same wide flange section weighs the same cambered or straight, so it lands in the estimate as a per-beam fabrication adder on the structural steel line rather than a measured quantity. Many estimators also carry a small concrete flood allowance on composite floors, because even correctly cambered beams rarely land perfectly flat, and that allowance belongs in the concrete line where it stays visible, not buried in the steel price.

How is steel camber put into a beam?

Steel camber is put in at the fabrication shop, before the beam ships, and a shop has two ways to do it. The curve can be rolled in cold, the method called cold cambering. Or it can be heat-set, which is what the phrase heat cambering steel beams refers to. Either way the callout on the plan is the same camber dimension next to the beam size, so the method does not change the takeoff.

What is pre-camber on a beam?

Pre-camber is the same upward curve, named for when it goes in. The framing plan specifies it, the shop builds it into the beam before the beam ever carries the deck and the wet concrete, and that is what the pre in pre-camber means. A pre-camber callout reads like any other camber callout, a note such as C = 3/4 in next to the beam size, and that note is what tells the shop to build a pre-cambered steel beam instead of a straight one.

Worked example

A worked beam camber example

Worked example

A framing plan shows 24 composite floor beams on 40 ft spans, each tagged C = 3/4 in. Step 1, camber adder: at an illustrative shop adder of $40 per beam, 24 beams x $40 = $960 on the structural steel line. Step 2, what skipping it costs in concrete: if those beams deflect 3/4 in at midspan, the finishers flood extra concrete to hold a level floor. Average extra thickness over a parabolic deflection is about 2/3 of the midspan value, so 0.75 in x 2/3 = 0.5 in. Step 3, tributary area: 24 beams x 40 ft x 10 ft tributary width = 9,600 sf. Step 4, extra volume: 9,600 sf x 0.5 in / 12 = 400 cf, and 400 cf / 27 = 14.8 cy, carried as 15 cy. Step 5, at an illustrative $185 per cy, 15 cy x $185 = $2,775 of unplanned concrete, roughly triple what cambering the beams would have cost.

How Ruh handles it

How Ruh handles camber.

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Camber: frequently asked questions

Does camber change the weight or tonnage of a steel beam?+

No. Camber is curvature, not added material, so a cambered beam carries the same section, length, and weight as a straight one. It is a shop labor and equipment operation priced per beam, which is exactly why tonnage-based pricing misses it. If your steel budget is built purely on dollars per ton, audit the framing plans for camber callouts and add the per-beam adders separately.

Why does mis-set camber cause a concrete overrun in the slab?+

If a composite beam is under-cambered or shipped straight, it deflects below the target slab elevation under the wet concrete, and the finishers must flood extra concrete to reach a level finished floor. Over-cambering creates the opposite problem, a high spot with thin slab over the beam that can violate the minimum thickness over the deck. Either way the concrete quantity moves, which is why the camber callout is an estimating issue and not just a fabrication detail.

Which beams typically get cambered and which do not?+

Camber typically shows up on longer interior composite floor beams where dead load deflection would otherwise be visible in the slab. Spandrel and edge beams, beams with moment connections, cantilevers, and short infill beams are usually left straight, because end restraint or short spans make the deflection small or hard to predict. Shops also commonly decline very small cambers, so check the general notes for the minimum the fabricator will set before counting every callout as an adder.

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Related terms

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