Girder
The main horizontal member that collects beams and delivers load to columns.
Quick Answer
A girder is a large primary horizontal member that supports beams or joists and transfers their load to columns or walls. In steel framing it is usually a heavy wide flange shape or a built-up plate girder. Estimators take girders off framing plans by linear feet and weight per foot, then convert to tons.
The Full Picture
In a framed floor or roof, load travels from the deck to secondary beams or joists, and from those into girders, which carry it to the columns. A girder is simply the member that other members frame into. The word describes a role, not a shape: the same W24 can be a beam in one bay and a girder in the next, depending on what bears on it. In practice girders are the deepest and heaviest members in a bay.
Steel girders take several forms. The most common is a rolled wide flange shape. Longer or heavily loaded spans use built-up plate girders, welded from plates so the depth and flange size can be tailored. Pre-engineered and joist-framed buildings often use Joist Girders, a truss-type member designed to carry joists, which are covered in the Steel Joist Institute standard. Concrete and timber buildings have girders too, but the term here is about steel takeoff.
On the drawings, girders appear on the framing plans, each tagged with its size, such as W24x68, along with camber and connection marks. Beam and girder schedules or the framing elevations may repeat the information, and column schedules show how the girder lands. Estimators should read the connection details too, because girder-to-column moment or shear connections can add material and fabrication that is not visible in the member size alone.
The takeoff unit is linear feet by shape, multiplied by the weight per foot from the shape tables, giving pounds and tons. Girders are then often counted by each for erection, since crane picks and field labor follow piece count more than weight. Connection material, such as clip angles, shear tabs, stiffeners and bolts, is commonly carried as an added percentage or as a separate counted item, and the estimate should say which approach was used so it is not double counted.
Real Examples
Common Misconceptions
People assume: A girder is a special kind of steel shape.
Actually: It is a structural role. Rolled wide flange shapes, built-up plate sections and Joist Girders can all act as girders, so the drawings, not the name, tell you what to price.
People assume: Girder weight is just length times weight per foot, and that's the whole cost.
Actually: That gives the member weight only. Connections, stiffeners, camber, shop fabrication and field erection are priced on top, and heavy girders may need larger crane picks.
Does MeltPlan Solve This?
Partially — adjacentMeltPlan's takeoff pulls quantities from PDF plans, and US-based estimators review and adjust them, which covers counting and measuring members from framing plans. Pricing the steel, connections and erection remains your estimate.
Get girder and beam lengths pulled from your framing plans →Frequently Asked Questions
What is the difference between a girder and a beam?
A girder is a primary member that supports beams or joists, while a beam is the secondary member that frames into it. Both can be the same shape, so the difference is the role on the framing plan.
How do you take off steel girders?
Measure each girder's length from the framing plan, group by shape, multiply linear feet by the weight per foot, and convert pounds to tons. Count the pieces separately for erection and carry connections consistently.
What grade is used for girders?
Rolled wide flange girders are normally ASTM A992, while built-up plate girders use the plate grade in the structural notes. Read the general notes and spec section instead of assuming.
Where are girders shown on the structural drawings?
On the framing plans, with size and mark tags, plus elevations, connection details and sometimes a beam schedule. Foundation and column schedules show where they land.
What is a Joist Girder?
A Joist Girder is a truss-type steel member designed to support open web joists. It is covered by the Steel Joist Institute standard and is priced differently from a rolled shape, so check how the drawings and your supplier quote it.