Construction glossary · Steel and structural
What is girder in construction?
A girder is the primary horizontal member in a steel frame that carries other beams: infill beams frame into the girder, and the girder frames into the columns. Estimators take girders off by member from the framing plans, multiplying the weight per foot in the shape callout (a W24x76 weighs 76 lb per foot) by the member length, then converting total pounds to tons for pricing.
Updated June 2026 · Reviewed by the Ruh construction team
Where a girder sits in the frame
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Book a walkthroughA girder is the primary horizontal member in a structural steel frame: beams frame into girders, and girders frame into columns. On commercial jobs the girders show up on the structural framing plans (the S2xx series in most sets) with a callout like W24x76, where W means wide flange, 24 is the nominal depth in inches, and 76 is the weight in pounds per linear foot. The steel fabricator details girders on shop drawings, the erector sets them in the field, and the GC's or steel sub's estimator takes them off by member during bidding. New estimators trip over a few predictable things: confusing girders with the beams that load them (both look identical in section, the hierarchy lives in the plan), missing the connection material and stiffeners that ride along with girders at moment frames, and reading the span as the grid dimension when the actual member length is grid minus the column depth and setbacks. Because girders are heavy relative to infill beams, a missed or double-counted girder line moves the tonnage, and the bid, more than almost any other single member.
Girders are taken off by member from the structural framing plans, cross-checked against the beam schedule and the column grid. The takeoff unit is weight: pounds per linear foot from the shape designation times the member length in feet, summed and divided by 2,000 to get tons. Fabrication and erection are both priced per ton, so the estimate carries girders inside the structural steel tonnage line rather than as a separate trade. Convention is to add a connection allowance, commonly somewhere around 8 to 12 percent of net member weight, to cover clip angles, plates, and bolts that the plans do not quantify, and to round the final tonnage up to two decimals or the nearest tenth. Quantities should tie back to the AISC shape weights, not scaled guesses.
Worked example
Take a one-story office floor with 8 interior girders, all W24x76, each spanning 32 ft column to column. Step 1, weight per girder: 76 lb per ft x 32 ft = 2,432 lb. Step 2, total weight: 8 girders x 2,432 lb = 19,456 lb. Step 3, convert to tons: 19,456 lb divided by 2,000 lb per ton = 9.728 tons, carried as 9.73 tons. Step 4, price it: at an illustrative $2,800 per ton for fabrication plus $900 per ton for erection, the combined rate is $3,700 per ton, so 9.73 tons x $3,700 = $36,001 for the girder package before connections, deck, and fireproofing. Connection material is usually carried as a percentage allowance on top, often around 10 percent of member weight, which would add roughly 0.97 tons here.
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How Ruh handles girder
Ruh reads the structural framing plans, identifies each girder by its shape callout, and runs the weight per foot times length math to build the steel tonnage. It prices that tonnage against the contractor's own price book, using their real per-ton fabrication and erection costs rather than canned national figures. The estimator reviews the member list, adjusts the connection allowance if needed, and signs off before the number enters the bid.
See construction estimating softwareGirder: frequently asked questions
What is the difference between a girder and a beam?+
Both are horizontal members, and in steel they are often the same wide flange shapes. The difference is hierarchy: beams carry the deck or joists and deliver their load to girders, while girders carry those beams and deliver the load to columns. On a framing plan the girders run along the column lines and the infill beams frame into their webs, which is why girders are typically the heavier shapes in any bay.
How do I figure the weight of a girder from its callout?+
The shape designation gives it to you directly. A W24x76 is a wide flange, nominally 24 inches deep, weighing 76 lb per linear foot, so a 30 ft piece weighs 30 x 76 = 2,280 lb. Multiply weight per foot by length for each member, sum the pounds, and divide by 2,000 to get the tons that fabrication and erection are priced on.
Do girder quantities include connections and stiffeners?+
Not from the shape weight alone. The per-foot weight covers only the rolled member, so estimators add a connection allowance, commonly in the range of 8 to 12 percent of net weight depending on the connection types, to cover clips, plates, bolts, and stiffeners. Moment connections and heavy gusset work push that allowance higher, which is one reason two bids on the same plans can show different tonnages.
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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.