Structural steel takeoff

Rolled shapes (W, S, M, HP, C, MC, angles, hollow sections, and pipe) are taken at their nominal published weight per foot times the detailed length from the shop or erection drawings. The designation already encodes the weight: a W14x30 is 30 pounds per foot, never re-derived from the cross-section. In metric regions the same applies as mass per metre from the standard section tables. Plates are computed to the smallest enclosing rectangle: overall rectangular dimensions times thickness times density. The triangular drop from a gusset, a sheared corner, or a clipped end is not removed, because that waste is real material the fabricator bought.

This is the AISC Calculation of Weights method, restated almost verbatim by US highway specifications such as Caltrans Standard Specifications Section 55. The bid and most contract pay methods use this computed (theoretical) weight, not the actual weighed mass. Scale weight, the mass the mill weighs at the heat, can exceed theoretical weight by the rolling margin. ASTM A6 sets that margin as a permissible limit, not a guaranteed overrun: up to plus 2.5 percent on shapes of 100 pounds per foot and heavier, and minus 2.5 to plus 3.0 percent on shapes under 100 pounds per foot. Treat it as a tolerance band for reconciliation, not an expected average; using scale weight where the contract specifies computed weight over-bills the work.

Heavy plate carries a larger rolling tolerance, so on highway and bridge pay methods plates wider than 36 inches (about 915 millimetres) take an add of one-half of the ASTM A6 permissible weight overrun on top of their nominal rectangle weight. Plates 36 inches and narrower take no add. Metric building methods measure net theoretical mass and do not apply this overrun.

No deduction is taken for copes, blocks, clips, sheared edges, punching, drilling, boring, milling, or planing. The mill rolled the full section and the fabricator paid for the full bar or plate, so the removed material is scrap, not a credit. ANZSMM states it as no deduction for holes or notches, and the same principle holds across the formal methods, even for large holes or notches in a rolled member.

The no-deduction rule is absolute for member features but not for plated areas. Large openings cut into a plated field, such as a deck or a base-plate field, follow the general method small-void rule borrowed for steel area: deduct openings above roughly 0.10 square metre under the civil method (CESMM4) and above 1.00 square metre under the building method (RICS NRM2). There is no steel-specific opening clause, so these general thresholds are applied by analogy. Stair, shaft, and elevator openings in deck are always deducted; small penetrations are absorbed.

Weld metal weight and paint or galvanizing weight are not computed into the steel tonnage. Both are negligible against the member steel and are priced as their own lines: welds by length and size as described under AWS D1.1, and coatings by surface area. Bolts, nuts, washers, and studs, when weighed, come from the AISC Steel Construction Manual fastener tables (weight per 100 count); otherwise they fall inside the connection allowance. At bid stage the final connection designs are usually unknown, so connection steel (gussets, shear tabs, base and cap plates, stiffeners, clip angles, bolts) is covered by a flat percentage added to the bare member weight. Common practice runs from 3 to 10 percent, often 5 to 7 percent for ordinary shear-connected building frames and roughly 10 to 15 percent for moment, braced, or seismic frames. This percentage is an estimating convention with no published clause behind a specific number, so calibrate it against fabricator history; the formal methods measure connections separately when the designs exist.

Two countable connection items get their own lines. Anchor rods (anchor bolts) under ASTM F1554 grades 36, 55, and 105 are a procurement-and-set quantity derived from the column and base-plate count (commonly four rods per base plate), described by diameter, embedment, projection, and grade, and usually set by the concrete trade ahead of erection. Headed shear studs (AWS D1.1 Type B, commonly three-quarters of an inch) are a high-volume composite-floor item taken each from the composite-design stud schedule, with weight from the AISC tables, never added to bare-member tonnage.

Member weight is length times weight per foot, so the length convention drives the tonnage. The method uses the overall length of each shape, end to end, with no deduction for end preparation. ANZSMM measures sections in 0.1 metre multiples; US imperial practice rounds to the nearest inch or part-foot. Columns are measured between splice points, and beams run center of support to center of support or to the detailed cut length.

On a framing or foundation plan, a structural column is a solid-filled square or rectangle, a heavy I or W shape, or a hollow-section or pipe symbol at a grid intersection. Count one point per column. Base plates are counted with the column, not separately, and architectural posts, bollards, embeds, and non-structural columns are excluded. A column spliced over several stories is one column for the count and for tonnage, and anchor-bolt and base-plate counts derive from it as a cross-check.

A separate count rides alongside the column lines: the erection-piece count, taken per shippable or field-connected piece. Erection labor and crane picks are driven by the number of pieces, not continuous members. A three-story column spliced at level two is one member but two erection pieces, and a girder shipped in two sections is two picks. Track the piece count for erection man-hours, independently of tonnage.

Different member roles carry different fabrication and erection labor per ton, so tonnage is grouped rather than lumped: columns, beams and girders, braces, secondary and infill members, and miscellaneous metals and embeds, plus a shop-versus-field split. The formal methods require columns, beams, bracing, and irregular members to be measured separately. Miscellaneous metals such as stairs, ladders, railings, lintels, and embeds are usually a separate package from the structural framing.

Tonnage is also segregated by steel grade, because grade drives unit price and procurement lead time. W shapes are ordinarily ASTM A992, plate is commonly A36 or A572 Grade 50, hollow sections are A500 or A1085, and round pipe is A53. The same shape in a higher grade is a different procurement line. In Europe the equivalent grades come from EN 10025, and in Australia and New Zealand from the AS/NZS grades. Confirm the grade against the project material specification on the structural sheets.

Metal deck is taken by area over the supported framing to the outer edge of the deck bearing, in squares (100 square feet) in the US or in square metres elsewhere. The area is converted to a panel quantity using the net coverage width published by the Steel Deck Institute under ANSI/SDI SD-2022, not the nominal width: a common 36-inch roof-deck panel nests to a net 36 inches, while composite floor deck with interlocking side laps covers slightly less than nominal. The deck waste allowance, typically 5 to 10 percent for cut-to-fit at openings, slope, and end laps, is convention rather than a published figure.

Open-web steel joists and joist girders (the SJI K, LH, DLH, and KCS series) are taken each and by length, with weight from the SJI load-table approximate weight in pounds per foot for each designation, for example 22K9. That weight excludes bridging and accessories, so bridging is a separate line. Bar grating, checkered and floor plate, and stair treads are miscellaneous-metals items taken by area with their own cut and waste conventions, plus edge banding by length and treads and landings each; their weight comes from the manufacturer's product weight per area, such as the NAAMM/MBG grating series, not rolled-section tables.

Coatings are not a function of steel weight. Spray-applied fireproofing, intumescent coating, and shop or field paint are taken by surface area, the developed perimeter (girth) of each section times its length. Fireproofing thickness depends on the section factor and the required fire rating, set by the listed fire-resistance design; UFGS 07 81 00 governs the scope of spray-applied fireproofing. Hot-dip galvanizing is usually measured by member surface area like paint, while the deposit is specified as a coating mass per unit area under ASTM A123, and galvanizers often price by the weight of steel dipped.

For takeoff weight, hollow sections and pipe still use the published nominal weight per foot, so the tonnage basis is unchanged. The trap is that the ASTM A500 design wall is about 0.93 times the nominal wall, which reduces the design section properties (area and modulus) even though the catalog weight is at the nominal wall. Do not recompute takeoff weight from the design wall, because that would understate the purchased mass. Confirm per table which wall a published value reports.

Architecturally exposed structural steel is steel left visible where appearance matters. The AISC Code of Standard Practice defines exposed-steel categories that escalate fabrication and finishing requirements, such as smoother welds, ground edges, and tighter tolerances. This does not change the measured weight, but it carries a fabrication-cost premium that should be flagged so the surcharge routes only to the exposed members. Treat it as a categorization flag on otherwise-standard tonnage, not a quantity change.

The same frame yields different tonnage depending on the purpose. A bid estimate loads the net computed member weight with the connection allowance and the drop or scrap allowance, and takes deck and joists by area or each with their own waste. Procurement orders members in mill stock lengths (commonly 40, 45, 50, and 60 feet) and nests them to minimize the un-nested remainder, the drop, so the ordered weight exceeds the net by that drop, often modeled as a 3 to 8 percent allowance.

Progress billing and measured-for-payment, especially on highway work, use the codified computed weight only: plates to the rectangle, the one-half ASTM A6 overrun on wide plate, no deductions, and no weld or paint. Cost control reconciles the fabricator's scale weight against the computed contract weight within the ASTM A6 rolling margin. The connection allowance and the drop allowance belong only to bid and ordering, never to the measured-for-payment quantity. Exayard reads the plan set and the steel schedule, applies these rules by member role and grade, and records the standard behind each quantity so the weight can be re-measured and defended.