Structural steel takeoff

What it calculates

• Mass of each member: length × mass per metre × number
• Plate and flat by area: length × width × thickness × 7.85 kg per m² per mm
• Class per line: light, medium or heavy from mass per metre, or by section and member type
• Tonnes by area and class, with a check that every kilogram is allocated

How to measure it, step by step

1. 01

   Set the job and the class limits

   On Project, enter the job, the drawing set and its revision. Then set the light and heavy limits in kg/m to match the preambles of the bill you are pricing.

   Why: Light, medium and heavy steel carry different rates per tonne, and bills draw the line in different places. The source template had two sets of limits, 25/50 and 30/60, on different sheets. One input removes the doubt.

2. 02

   Name the areas of the bill

   List up to six areas on Project, such as main frame, roof, crane gantry or stairs.

   Why: Splitting the tonnage by area shows the client where the steel sits, and lets a variation be valued against the right part of the bill.

3. 03

   Take off one line per member type

   On Takeoff, pick the area and the section from the drop-downs. Then enter the length of one member in metres and the number off.

   Why: Mass is length × mass per metre × number. Take lengths from the general arrangement drawings, not the fabricator's cut list, so you measure the design rather than the shop's offcuts.

4. 04

   Measure plate and flat by area

   For base plates, gussets and flats, pick the plate thickness from the library, then enter length and width in metres. For a shaped gusset, enter the smallest rectangle that encloses it.

   Why: Plate is measured by area × thickness. At 7 850 kg/m³, steel weighs 7.85 kg per square metre for every millimetre of thickness, so a 350 × 350 × 20 base plate is 19.2 kg. SANS 1200 H (clause 8.2.3) measures gussets on their minimum enclosing rectangle, but large shaped plates such as a tank bottom at their net size.

5. 05

   Check each line's class

   The class fills itself in: HS for hollow sections, CR for cold-formed, PL for plate. Everything else goes light, medium or heavy by mass per metre. Use the override column only where your bill bills a member type on its own, such as crawl beams or trestles.

   Why: A crawl beam can be a heavy section and still be billed under its own item. Letting the mass decide by default, and overriding only on purpose, means the summary shows any override you made.

6. 06

   Read the summary into the bill

   Summary gives tonnes by area and class to three decimals. The check line compares it with the takeoff total and shows any steel left without an area.

   Why: Bills price steel per tonne. A non-zero unallocated figure tells you a line has no area before the client's QS finds it.

Measuring rules

Measure nett mass

Measure the members as drawn, at the nominal mass per metre in the SAISC section tables, or at 7 850 kg/m³ where a section is not listed. Ignore rolling margins. Make no deduction for bolt holes, milling or planing, and no addition for waste, weld metal or shop fasteners (SANS 1200 H, clauses 8.2.1 and 8.2.2).

Add the fittings to the members

Cleats, gussets, battens and stiffeners are measured and their mass added to the member they belong to (SANS 1200 H, clause 8.2.1). Take them off as plate lines in the same area rather than adding a percentage, unless the bill's preambles say otherwise.

Split the bill the way the standard does

SANS 1200 H schedules supply and fabrication per tonne, with a separate item for each type of member and each structural position, subdivided where the jointing differs, such as welded against bolted (clause 8.3.1.2). Delivery, erection and corrosion protection are separate items (clauses 8.3.2, 8.3.3 and 8.3.13). The area and class columns give you the first split; note welded or bolted in the description where the bill asks for it.

Bolts are a separate item

Erection bolts are scheduled per tonne or by number, one item for each grade and type of bolt, with nuts and washers in the rate. Holding-down bolts get one item for each diameter, size and shape (SANS 1200 H, clauses 8.3.4 and 8.3.6). The bolt workbook in this pack gives their mass for checking a rate or a delivery.

Check unusual sections

The library masses come from the source template. Check any section you rely on, and any you add, against the SAISC Red Book or the mill's section tables.

Standards behind it

Measure to the document your contract names. Clause numbers are given only for the SANS parts read in full, and the wording is paraphrased: read the clause itself in your copy. Each card says how far that reference was checked.

More on which standard applies when: measuring standards for South African construction.

What we fixed in the source template

This workbook is rebuilt from a contractor template that was in use. These are the errors it carried, and what each does now.

• Eight of the thirteen classes (cold rolled, built-up, head and tail frames, stringers, trestles, cantilevers, vertical take-up and rails) had no per-line formula, so they always totalled zero. Every class now totals.
• The light / medium / heavy limits read 25/50 kg/m on the takeoff and 30/60 on the summary. They are now one input on Project.
• Flats returned #VALUE! because their width was stored as text. Plate and flat now take length × width.
• Two masses were stored as text with a comma decimal (45 × 45 × 3 angle, 114.3 × 4.5 CHS), so those lookups failed, and one CHS was listed twice. All three are corrected.
• The summary sheet was not linked to the takeoff, and the four named ranges were broken. Both are rebuilt.

Planning-stage quantities, not a final account or a quote. Check every quantity against the drawings and the bill’s preambles. General guidance, not professional or engineering advice.

Reviewed by Aidan Koetaan MBA PMP, quantity surveyor and construction project manager.