A structural steel material take-off (MTO) is a quantified list of the steel profiles, plates, bolts and other materials required for a structure, taken from the drawings or the model at a stated revision and measured on a stated basis. Procurement teams use it to order mill material and bolts. Planners use it to measure progress. Estimators use it to check costs. An MTO is only as reliable as two things printed on it: the source revision and the measurement basis.
What is the difference between an MTO, a BOM and a BOQ?
The terms overlap, and organisations use them differently. A common working distinction is:
| Term | Typical meaning | Typical user |
|---|---|---|
| MTO (material take-off) | Quantities extracted from design or detailing for ordering | Procurement, engineering |
| BOM (bill of materials) | Itemised parts list for a defined assembly or package, often from the detailing model | Fabrication, procurement |
| BOQ (bill of quantities) | Measured quantities for pricing a contract | Commercial, tendering |
Practitioners commonly note that the terms are used interchangeably on some EPC projects. Define them in your scope.
MTO stages on an EPC project
- 1Design or preliminary MTO. Taken from design drawings or the design model to support early mill orders and budgets. Connections and secondary steel are estimated by allowance.
- 2Advance bill or advance MTO. Produced early in detailing, once main members are modelled, so long-lead profiles can be ordered before shop drawings are complete.
- 3Detailed MTO or BOM. Generated from the numbered detailing model, covering all parts, plates, bolts and welds as modelled.
- 4Revision MTOs. Re-issued when design changes affect quantities, showing what has been added and deleted.
Taking off long-lead structural steel early lets mill orders be placed ahead of fabrication. That only works if the early MTO is clearly labelled with its assumptions.
What does a structural MTO list?
| Item | Typical fields |
|---|---|
| Profiles | Section designation, grade, length, quantity, unit weight, total weight |
| Plates | Thickness, grade, area or dimensions, weight |
| Hollow sections | Size, wall thickness, grade, length |
| Bolts, nuts and washers | Diameter, length, grade, coating, quantity, shop or field |
| Grating, handrail, stair treads | Type, area or length, quantity |
| Anchor bolts and embeds | Size, length, quantity |
| Summary | Weight by structure, area, phase or grade |
Measurement basis and allowances
Two MTOs taken from the same model can still differ, depending on:
- Weights: whether net weights are used, or gross weights including cut-outs and plate nesting losses.
- Lengths: whether lengths are exact member lengths or rounded to stock lengths.
- Allowances: whether a percentage is added for connections, wastage or contingency, and whether it is shown separately.
- Exclusions: whether welds, coatings, shims, grout or temporary steel are excluded.
State the basis on the cover sheet. Unlabelled allowances are a common source of disputes between engineering and procurement.
Reconciling quantities with revisions
- Tie every MTO issue to the input and model revision.
- Show changes since the last issue, both additions and deletions.
- Reconcile the MTO with the drawing register, so quantities only cover current, non-superseded assemblies.
- Keep a separate "on hold" quantity for areas awaiting design information.
Frequently asked questions
How accurate is a model-generated MTO?
It is as accurate as the model's content and the report settings. A fully detailed, numbered model gives a much closer quantity than a design-stage model with allowances.
Should bolts be in the MTO?
Usually, yes. Bolt quantities, split into shop and field bolts, are often needed early for procurement.
Can you produce an MTO without full detailing?
Yes, from design drawings or a design model, but the allowances for connections and secondary steel should be stated. Reinforcement quantities for concrete work come from the bar bending schedule instead.
Next step
PetroHill produces structural steel quantities, bills of materials and bolt schedules reconciled with the agreed source revision and measurement basis. See material take-offs, BOM and engineering documentation or request a quote.
References
Technical sources consulted. Standards are paid documents; confirm clauses against the licensed edition named in your project specification.
- Takeoff (construction) · Wikipedia (opens in a new tab)
- Q&A: Difference between BOM and MTO · ResearchGate (practitioner discussion) (opens in a new tab)
