How to Do a Steel Take-Off

Step 1: List every member from the drawings

Work through the structural drawings systematically - grid line by grid line, or drawing by drawing - and list every steel member: columns, beams, rafters, bracing, purlins, plates and cleats. Give each line an item mark (B1, C2, R1...) matching the drawings so the take-off can be checked later. The discipline matters more than the format: every member gets a line, and no line gets skipped.

Step 2: Record section, length and quantity

For each member record its section size (e.g. 310UB40.4, 89×89×5.0 SHS), its length in metres, and how many of that identical member the job needs. Identical members on a repeating grid are one line with a quantity, not ten lines.

Step 3: Convert to weight

Steel is bought and sold by weight, so every line converts to kilograms:

The kg/m figure comes from the section designation itself (the "40.4" in 310UB40.4) or from a steel weight table. Plate is calculated by area: kg/m² × width × length.

Step 4: Add allowances

Two allowances turn a theoretical weight into a buyable one:

• Waste - offcuts and mill lengths that don't divide evenly into your member lengths. Typically 5-10% depending on how well lengths nest.
• Cleats and connection material - end plates, cleats, stiffeners and gussets that aren't itemised on the drawings. Commonly allowed as a percentage of member weight (5-10% for typical portal-frame work).

Purlins are usually ordered cut-to-length, so most estimators apply no waste or cleat allowance to them.

Step 5: Coatings

Galvanising is priced per tonne of the steel dipped, so it follows the weight already calculated. Painting is priced per square metre of surface area, which depends on the section profile - a surface area table (m² per metre) converts each painted member's length to paintable area.

Step 6: Bolts and connections

Count connection bolts per member end - a simple shear connection on a small beam might take 2-3 bolts per end, deeper members more, and moment (portal) connections add flange bolt groups on top. Multiply by member quantity and price per bolt supplied.

Step 7: Price it

With weights, areas and counts done, the estimate is rates × quantities: supply rates per tonne by section family, fabrication hours, coating rates, drafting, and margin. Typical Australian ranges are covered in structural steel cost per tonne.

Common take-off mistakes

• Missing members that only appear on one drawing (bracing, trimmers and lintels are the classic ones).
• Using overall grid dimensions instead of actual member lengths.
• Forgetting that waste applies to what you buy, not what you install.
• Pricing painted area from weight instead of surface area - profiles with high area-to-weight ratios (angles, light channels) burn you.
• No item marks, making the take-off impossible to check against the drawings.