Steel Quantity Takeoff — Estimation & Benchmarking Guide
How to prepare a structural steel quantity schedule: takeoff categories, kg/m^2 benchmarks by building type, waste allowances, and cost estimation methods.
What is a steel takeoff?
A steel takeoff is the process of extracting quantities from structural drawings to determine the total tonnage of steel required for fabrication and erection. The takeoff forms the basis of the fabricator's bid, the estimator's budget, and the engineer's weight check. An accurate takeoff must account for every member, connection plate, stiffener, shim, and miscellaneous item.
Steel quantity is typically expressed as kg/m^2 of gross floor area (or lb/ft^2 in the US). This metric allows comparison between buildings of different sizes and benchmarking against industry norms.
Takeoff categories
A complete structural steel takeoff includes:
- Primary members — beams, girders, columns, bracing, trusses. These represent 60-75 percent of total tonnage.
- Secondary members — purlins, girts, stair stringers, platform framing, elevator framing, lintels. Typically 10-15 percent of total.
- Connection material — gusset plates, stiffeners, shear tabs, end plates, base plates, splice plates, bolts, welds. Connection material adds 8-15 percent to primary member weight. This is often missed in preliminary estimates.
- Miscellaneous steel — handrails, ladders, access platforms, embed plates, pipe supports, equipment bases. Ranges from 3-8 percent depending on building function.
- Deck — metal deck (composite or roof) is sometimes included in the steel takeoff, sometimes separate. Clarify scope early.
Benchmarks by building type
| Building type | Typical steel weight (kg/m^2) | Typical steel weight (lb/ft^2) | Primary system |
|---|---|---|---|
| Low-rise office (3-6 stories) | 30-45 | 6-9 | Composite beams + braced core |
| Multi-story car park | 25-35 | 5-7 | Long-span beams + braced frames |
| Industrial warehouse | 20-35 | 4-7 | Portal frames |
| Retail / shopping center | 35-50 | 7-10 | Long-span trusses |
| High-rise office (20-40 stories) | 40-60 | 8-12 | Moment frames + outriggers |
| Hospital | 50-70 | 10-14 | Moment frames, heavy MEP loading |
| Data center | 60-90 | 12-18 | Heavy floor loads, redundant structure |
These benchmarks include connection material and miscellaneous steel. Seismic regions add 10-20 percent over non-seismic designs.
Worked example — warehouse takeoff estimate
Building: 60 m x 120 m warehouse, 10 m eaves height, portal frames at 7.5 m spacing, no mezzanine.
Gross floor area = 60 x 120 = 7,200 m^2. Using a benchmark of 28 kg/m^2 for a simple portal frame warehouse:
Estimated steel tonnage = 7,200 x 28 / 1,000 = 201.6 tonnes.
Breakdown estimate: Rafters and columns (primary) = 201.6 x 0.68 = 137 t. Purlins and girts = 201.6 x 0.14 = 28 t. Connection material = 201.6 x 0.10 = 20 t. Miscellaneous (bracing, handrails, access) = 201.6 x 0.08 = 16 t.
Cost estimate at $2,800/tonne fabricated and erected (typical 2025 US market): 201.6 x $2,800 = $564,500.
Cross-check: at 16 portal frames (120/7.5 = 16 bays, 17 frames including end frames, say 16 typical + 2 end gable frames), each typical frame might use: 2 x 530UB82 columns x 10 m = 1.64 t, 2 x 530UB82 rafter halves x 31 m = 2.54 t, haunches 0.3 t, connections 0.2 t. Total per frame approximately 4.7 t. 16 frames x 4.7 = 75 t for primary frames. Add end walls, purlins, bracing, and misc = total approximately 190-210 t. Consistent with the benchmark estimate.
Waste and contingency factors
| Item | Allowance | Reason |
|---|---|---|
| Cutting waste | 2-5% | Off-cuts from standard lengths |
| Detailing growth | 3-8% | Stiffeners, haunches, and plates added during detailed design |
| Fabrication tolerance | 1-2% | Shimming, fit-up adjustments |
| Design contingency | 5-10% | Scope changes, load increases during design development |
A preliminary estimate should include at least 10 percent contingency. At tender stage, waste should be itemized explicitly.
Code references for self-weight
| Standard | Self-weight provision | Reference |
|---|---|---|
| ASCE 7-22 | Dead load includes weight of all permanent construction | ASCE 7-22 Cl. 3.1 |
| AS 1170.1 | Permanent actions include structural self-weight | AS 1170.1 Cl. 2.2 |
| EN 1991-1-1 | Self-weight of structural elements as permanent action | EN 1991-1-1 Cl. 2.1 |
| NBCC | Dead load includes weight of structural members | NBCC 4.1.4 |
All codes require that the self-weight used in analysis matches the actual weight of the designed members. If the final design is significantly lighter or heavier than assumed, the analysis must be re-run.
Common pitfalls
- Omitting connection material from the estimate. Connections add 8-15 percent to primary member weight. A 200 tonne estimate becomes 225 tonnes with connections included. Fabricators price on total tonnage.
- Using benchmarks from the wrong building type. A warehouse at 28 kg/m^2 and a hospital at 60 kg/m^2 differ by more than a factor of two. Always select the benchmark that matches the actual occupancy and structural system.
- Ignoring fire protection weight. Spray-applied fireproofing adds 10-20 kg/m^2 to dead load and must be included in the structural analysis, even though it is not part of the steel takeoff.
- Confusing gross floor area with footprint area. A 5-story building with 1,000 m^2 footprint has 5,000 m^2 gross floor area. Benchmarks use gross floor area. Using footprint area inflates the kg/m^2 figure by the number of stories.
Run this calculation
Related references
- Structural Steel Weights
- Framing Systems
- Steel Grades
- How to Verify Calculations
- steel beam capacity calculator
Disclaimer
This page is for educational and reference use only. It does not constitute professional engineering advice. All design values must be verified against the applicable standard and project specification before use. The site operator disclaims liability for any loss arising from the use of this information.