A GC is pricing a 60,000 SF steel-framed flex office building. Three structural steel bids come back, and the spread between low and high is 18–20%. The GC has no tonnage number of his own, so he can't tell whether the spread is price or scope. The low bidder might be sharp, or might have left out half the stairs.
That's the case for running your own steel takeoff. Most GCs don't fabricate or erect steel, and you aren't trying to replace the steel sub. You take off steel to budget early, sanity-check fabricator bids, and level scope before you award.
This guide walks through five stages:
- Organize the plan set and specs.
- Read the structural drawings and identify every member.
- Count, measure, and convert to tons.
- Add what the drawings don't show.
- Turn tonnage into a budget and level the bids.
Why GCs Run a Steel Takeoff When a Fabricator Will Price It Anyway
You have three reasons to do your own takeoff. You need an early budget before a fabricator will give you a number. You need a sanity check on the bids you receive. And you need a baseline for leveling scope across them.
What a GC-Level Steel Takeoff Actually Delivers
You're producing three things: tonnage by member type, a rough allowance for connections and misc steel, and a list of scope items to confirm. It's a budget-grade number, not a detailing-grade number.
A detailer models every piece, connection, and bolt. You're measuring what the structural drawings show and adding a reasoned allowance for what they don't. That's enough to judge bids. It isn't enough to fabricate from.
The Cost of Skipping It
Without a tonnage baseline, a low bid and an incomplete bid look identical. One GC on a mid-size project told us: "Our low steel bidder was 14% under the next guy. We were thrilled until the shop drawings showed up and the stairs and lintels weren't in there. By the time we plugged those holes, he wasn't low anymore."
A baseline wouldn't have told him the price was wrong. It would have told him to ask what was missing before award.
Stage 1: Organize the Plan Set Before You Count a Single Beam
Input: the full drawing set and specs. Output: a checklist of every sheet and spec section that touches steel. Good construction plan set organization saves hours here, because steel is scattered across more sheets than most people expect.
Pull Every Sheet That Carries Steel
Start with the S-series: general notes, foundation plans, framing plans by level, roof framing, elevations, sections, and details. Then hunt through the architectural and civil sheets for steel that never makes it onto a structural plan.
The usual culprits are stairs, canopies, lintels over openings, equipment supports, and rooftop screens. Write each sheet number on your checklist with what it contributes.
Read the CSI Spec Sections That Define Scope
Specs set requirements the drawings don't. The CSI spec sections construction estimators check first for steel are:
- 05 12 00 Structural Steel Framing
- 05 21 00 Steel Joist Framing
- 05 31 00 Steel Decking
- 05 50 00 Metal Fabrications
- 09 96 00 High-Performance Coatings, and the related fireproofing sections (07 81 00 for spray-applied)
These sections tell you about AISC certification for the fabricator, galvanizing, shop primer, and who furnishes anchor bolts. None of that shows up on a framing plan, and all of it moves price.
Log Addenda and Revisions First
Steel is revision-sensitive. A single added brace or upsized column changes both tonnage and connections. Before you measure anything, confirm the sheet revision in each title block against the latest addendum log, and note the revision date on your takeoff.
Stage 2: How to Read Structural Drawings for a Steel Takeoff
Input: the organized S-sheets. Output: every steel member identified by size and location. If you're still learning how to read structural drawings, the fastest route is to learn the callout language once, then apply it consistently.
Decoding Member Callouts: W, HSS, L, C, and Joists
Each callout encodes shape, size, and often weight:
- W16x40: a wide-flange beam, nominally 16 inches deep, weighing 40 lb per foot.
- HSS6x6x1/4: hollow structural section, 6 by 6 inches with a 1/4-inch wall, about 19 lb per foot.
- L4x4x3/8: an angle with 4-inch legs and a 3/8-inch thickness, about 9.8 lb per foot.
- C and MC: channels, read the same way as W shapes.
- 24K10: a K-series joist, 24 inches deep. The 10 is a chord section number, not a weight. Get joist weights from the SJI load tables or the manufacturer.
For rolled shapes, the number after the "x" is your weight per foot, and that drives the whole conversion.
Construction Drawing Abbreviations You'll Hit on Every Steel Set
Misreading construction drawing abbreviations changes the count. The ones that matter most:
- TOS / BOS: top and bottom of steel elevation. Misreading these shifts your column lengths.
- TYP: typical. It means the detail repeats, so count every instance.
- CJP: complete joint penetration weld, a cost driver.
- EOR: engineer of record, the person to ask when notes conflict.
- CAMB: camber. It's a fabrication requirement, not a length change.
Keep the abbreviation legend from the general notes sheet next to you. Engineers vary.
Confirm Blueprint Scale Before You Measure
Scale is where good takeoffs quietly go bad. Plans get resized when printed or exported, and a "1/8" = 1'-0"" label becomes meaningless. Details are often NTS (not to scale) or drawn at a different scale than the sheet.
The check takes 30 seconds. Find a long dimension string on the sheet, measure it with your tool, and compare. If the two don't match within about 1%, recalibrate before you count anything.
Stage 3: Count and Measure by Member Type, Then Convert to Tons
Input: identified members. Output: a tonnage schedule by member category and floor. For the general method behind any trade, see our construction takeoff guide.
Work in a Fixed Order: Columns, Beams, Bracing, Joists, Deck
Pick a sequence and repeat it on every level: columns, then beams and girders, then bracing, then joists, then deck. Mark off members on the plan as you count them so nothing gets double-counted.
Sort by member size within each category. Fifty W16x40 beams summed as one line make the weight conversion a single multiplication instead of fifty.
From Linear Feet to Tons Using AISC Weights
The math is length times pounds per foot, divided by 2,000. Take 1,200 LF of W16x40: 1,200 × 40 = 48,000 lb, which is 24 tons. Run this for every size, then sum by category and level.
Pull weights from the shapes tables in the AISC Steel Construction Manual. Rolled shapes can legally vary from nominal weight; ASTM A6 allows roughly 2.5%, so don't chase decimals on a budget-grade number.
Plates, Base Plates, and Stiffeners Add Up
Steel plate weighs about 40.8 lb per SF per inch of thickness. A 1-inch base plate at 18" × 18" is 2.25 SF × 40.8 = about 92 lb. Multiply that by 60 columns and you've found 2.75 tons you'd have skipped by only counting shapes.
Take plate items off by area and thickness, and give column base plates, cap plates, and stiffeners their own line.
Metal Deck Is a Separate Count
Metal deck is measured in square feet by gauge and profile, not tons. Fabricators often quote it separately or fold it into a different line. Mixing deck into your tonnage breaks the comparison against bids, so keep it in its own column.
Stage 4: Add What the Drawings Don't Show
Input: base tonnage. Output: adjusted tonnage and a list of unpriced items.
Connection Allowances
Connection material (plates, angles, bolts, welds) is rarely fully drawn at bid stage. Estimators cover it with a percentage allowance on base tonnage. As a rule of thumb, that figure often lands somewhere in the high single digits to mid-teens, but it isn't a standard.
Simple shear-tab framing sits at the low end. Moment frames and heavy bracing push it up. Confirm your number with a fabricator you trust on a comparable job before you rely on it.
How to Read Shop Drawings to Catch Takeoff Gaps
Shop drawings show what the structural set doesn't: actual connection details, piece marks, and often piece weights. After award, learning how to read shop drawings is how you close the loop on your bid-stage number. Compare the detailer's total tonnage and connection material against yours and investigate any gap over a few percent.
A superintendent who has walked a few steel jobs can spot a missing item in 30 seconds. Hand over the shop drawings and you'll hear something like, "Where's the loose lintel at the mechanical room?" Nobody sends them to the field before bid day, and that's the problem.
Misc Metals, Coatings, and Fireproofing
These get missed constantly:
- Usually the steel sub's scope: stairs, handrails, lintels, embed plates, shop primer, and galvanizing, if the specs call for them.
- Often separate trades: intumescent and spray-applied fireproofing, and field touch-up painting.
Check the spec and bid language on each. "Included by others" is where money hides.
Stage 5: Turn Tonnage into a Budget and Level the Steel Bids
Input: adjusted tonnage. Output: a $/ton budget check and a scope comparison across bids. This is the payoff stage.
Convert Tons to Dollars Using Your Own Numbers
Split your cost into furnish and fabricate, deliver, and erect. Apply $/ton figures from your company price book and recent bids, then add deck, joists, and misc metals as separate lines. Verify regional $/ton against current local bids rather than trusting national averages, because labor and mill pricing swing by market.
Then reverse the math on the bids you receive. Divide each by your adjusted tonnage. If the low bid implies a $/ton far below the others, that points to scope, not efficiency.
The Scope Gaps That Explain a 20% Bid Spread
Picture a GC estimating a 180-ton warehouse addition who gets three steel bids 20% apart. Divide each by the same adjusted tonnage and the low bid looks like a bargain. Read the inclusions and exclusions line by line and it usually isn't. The gaps that show up most often:
- Furnish-only vs. furnish-and-erect. One bid leaves erection, cranes, and the erector's equipment to you.
- Joists and deck. Some steel subs include them, and some carve them out to a separate supplier.
- Misc metals. Stairs, rails, lintels, and embeds drift in and out of the steel scope.
- Connection design. If the specs delegate connection design to the fabricator's engineer, one bid may carry it and another may not.
- Coatings. Shop primer is common; galvanizing, special finishes, and field touch-up often are not.
- Testing and inspection. Special inspection is usually the owner's or the GC's cost, but check each bid's language.
Put those lines in a table with each bid as a column, and fill every blank with your own cost before you compare totals. That is what leveling means: the comparison happens only after every bid covers the same scope.
Struvia helps on both ends of this. It takes off structural steel from the plan set and prices it from your own price book, and its bid leveling lines up steel sub bids against the same scope and flags exclusions. New accounts start with 600 free credits, no card.
Frequently Asked Questions
How do you do a steel takeoff from structural drawings?
Organize the sheets and specs first, then count and measure by member type in a fixed order: columns, beams, bracing, joists, and deck. Convert linear feet to weight using each member's weight per foot, add plates and a connection allowance, and then add the misc metals and coatings the drawings don't show.
How do you convert structural steel from linear feet to tons?
Multiply the length by the member's weight per foot, then divide by 2,000. The weight per foot is in the shape designation: a W12x26 weighs 26 pounds per foot, so 400 linear feet is 10,400 pounds, or 5.2 tons. For HSS, angles, and channels, take the weight from the AISC tables.
How much should I add for steel connections?
There is no fixed standard. Connection allowances commonly land somewhere in the high single digits to mid-teens as a percentage of base tonnage, lower for simple shear connections and higher for moment frames and heavy bracing. Confirm the number with a fabricator on a comparable job.
Should a GC do a steel takeoff if the fabricator prices it?
Yes. Your own tonnage is the baseline that lets you check each bid's dollars per ton and spot missing scope. Without it you can only compare bottom lines, and the lowest bid is often the one with the most exclusions.
What is usually excluded from a structural steel bid?
The most common exclusions are erection, joists and metal deck, misc metals like stairs and lintels, galvanizing or special coatings, fireproofing, connection design, and testing and inspection. Read every bid's exclusion list against the specs before you compare prices.
Steel is a tonnage trade, and tonnage is something you can check. Run your own takeoff, convert it to tons, and level every bid against the same scope before you award. To get the takeoff and the leveling in one place, upload a plan set free and run it on your next steel package.
*Reviewed by Weston Burnett, Co-Founder and CTO of Struvia.*
