How to do a structural steel takeoff from drawings

This guide explains general practice. It is not engineering advice. Quantities used for bids, orders or fabrication must be reviewed by a qualified professional against the project drawings, specifications and applicable standards.

What a structural steel takeoff is

A steel takeoff is the list of every structural steel member in a project, with its section, length and weight, organised so it can be priced, ordered and fabricated. It is the foundation of the steel estimate. Every error in the takeoff flows into the bid, the mill order and the shop schedule.

Most of the time in a manual takeoff is not spent on engineering judgement. It is spent searching: finding the next member, finding the sheet it is detailed on, reading a label that is half hidden by a leader line, and typing numbers into a spreadsheet. The method below is designed to make that searching systematic so nothing is missed.

Step 1. Assemble the full drawing set

Before counting anything, confirm you have the complete structural set and that every sheet is the same revision. A typical set includes:

• General notes (S-001 or similar): material grades, bolt types, connection design responsibility and typical details that apply everywhere.
• Foundation and framing plans (S-100 and S-200 series): the plan view of each level, showing beams, girders, columns and braces on the grid.
• Sections and elevations (S-300 series): braced frames, moment frames, column lines and anything that does not read clearly in plan.
• Details (S-400 and S-500 series): connections, base plates, stiffeners and special conditions called out from the plans.
• Schedules: column schedules, beam schedules, brace schedules and base plate schedules. These often carry the section sizes that the plans only reference by mark.

Also gather the architectural set for reference and the specification sections for structural steel, since they define what counts as structural versus miscellaneous metal.

Step 2. Decide how the takeoff is organised

Set the structure of your list before you fill it, because reorganising later is where errors creep in. A common structure is:

1. By level or area: Foundation, Level 1, Level 2, Roof. Matches the drawing sheets and makes reconciliation easy.
2. By member type within each level: columns, girders, beams, braces, then miscellaneous.
3. By section within each type: all W16×26 together, all W18×35 together, and so on.

Each line should carry at minimum: mark, section, count, length per piece, total length, weight per unit length, total weight, and the sheet and grid where you found it. That last column is the one people skip and the one that saves you during review.

Step 3. Identify every member on the framing plans

Work one plan at a time, grid line by grid line, in the same direction every time. Left to right along the letter grids, then top to bottom along the number grids. Mark each member off on the drawing as you list it, either with a highlighter on paper or a markup layer in your PDF tool. The goal is that any member you have not highlighted is visibly missing.

Look for:

• Columns: usually shown as small squares or I-shapes at grid intersections, often referenced to a column schedule.
• Girders: the heavier members spanning between columns.
• Beams and infill: lighter members framing into girders, often repeated on a regular spacing.
• Braces: drawn in plan as dashed lines or noted as "BF-1, see S-301"; the actual members are usually on the elevation sheet.
• Edge and spandrel members, lintels, and anything with a note like "see detail". These are the most commonly missed.

Step 4. Read section labels and marks

Every member should have a section designation, such as W16×26, HSS6×6×3/8 or ISMB 300, either written next to it or referenced through a mark. Capture both the section and the mark. When the plan shows only a mark, resolve it through the schedule and record which schedule you used.

Pay attention to notation conventions from the general notes. A label such as "W16×26 [12]" may mean a camber, a count, or a moment connection depending on the office standard. The typical-detail sheet usually explains this. When a label is illegible or contradicted by a schedule, flag it as a query rather than guessing.

Step 5. Get member lengths

Length is where takeoffs go wrong most often. Use sources in this order:

1. Dimensions on the drawing. Explicit dimension strings are authoritative.
2. Grid spacing. Most members span between grids. Grid dimensions are on the plan and are reliable.
3. Column schedule and elevations for column heights and brace geometry.
4. Scaling from the drawing, only when nothing else is available, and only after calibrating the scale against a known dimension on the same sheet. PDF scaling is often wrong after printing or reissue.

Decide up front whether you are recording grid-to-grid length or fabrication length. For estimating, grid-to-grid with a documented allowance is common. For ordering, fabrication lengths from the detailer are needed. Do not mix the two in one list.

When several members share a section and appear to share a span, do not assume they share a length. Check at least one member in each bay. Same section does not mean same length.

Step 6. Convert lengths to weight

Rolled sections are named by their weight per unit length, which makes this step straightforward:

For plates and built-up members, use volume multiplied by steel density (about 490 lb/ft³ or 7,850 kg/m³). Keep units consistent through the whole list, and state whether totals are in pounds, tons, kilograms or tonnes in the header.

Step 7. Add connections and miscellaneous steel

Main members are usually 85 to 95 percent of the steel weight. The rest is connections, base plates, stiffeners, gusset plates, anchor rods and miscellaneous items. Two approaches are common:

• Detailed takeoff: count plates, bolts and fittings from the details. Slower but more accurate, and needed for fabrication.
• Percentage allowance: add a documented percentage to the main member weight, based on the framing type and your own history. Moment frames and heavy bracing need more than simple shear-connected framing. Record the percentage and the reasoning so a reviewer can challenge it.

Separately list anything the specification defines as miscellaneous metal, such as stairs, handrails, lintels and embed plates, since these are often priced or subcontracted separately.

Step 8. Check the takeoff

A takeoff nobody has checked is a draft. Reasonable checks include:

• Reconcile against schedules. If the column schedule lists 24 columns and you have 22, find the two.
• Count by grid. Each bay on a regular framing plan should have a predictable number of infill beams. Bays that do not match get a second look.
• Weight per square foot or square metre. Compare the total to typical values for the building type. A number far outside the normal range usually means a units error or a missed level.
• Second person review. Ideally someone who did not do the takeoff, walking the highlighted drawings against the list.
• Query log. Every illegible label, missing dimension or conflict between plan and schedule goes on a list for the engineer of record.

Worked example

One bay of a Level 2 framing plan, imperial units, grid-to-grid lengths:

Values are illustrative. Note the source column: every number can be traced back to a sheet and grid, which is what makes the review in Step 8 possible.

Common mistakes

• Taking off from a superseded revision.
• Missing members that only appear in sections or details, especially braces, lintels and edge members.
• Copying a length across all members of the same section without checking each bay.
• Scaling from an uncalibrated PDF.
• Mixing grid-to-grid and fabrication lengths in one list.
• Forgetting to state units, or mixing pounds and kilograms across sheets.
• No record of where each member was found, so the review has to redo the search.