Erection Estimating: Why Piece Count Beats Tons
Steel erection estimating should start from piece count, not tonnage. A raising gang sets pieces, so labor and crane days scale with the number of picks and connections. Two 180-ton jobs can need very different crane time: one with 220 pieces, one with 600. Price both at the same dollars per ton and you'll lose money on the light one.
Why do tons alone mislead erection bids?
Tonnage is how steel gets bought, fabricated, and talked about, so it's tempting to price erection the same way. The problem is that a crane hook doesn't care what a piece weighs until it gets near the chart limit. Hooking on a 400 lb W8x18 infill beam takes nearly as long as hooking on a 3,000 lb W24x76 girder. Both need a tag line, a pair of connectors waiting at the steel, at least two bolts per connection before the load comes off the line, and a walk back to the shakeout.
So the number that drives your crew days is pieces, and the number that drives your bolt-up crew is connections. Tons only tell you which crane you need.
Here's how the same tonnage plays out across different piece weights:
| Job | Tons | Pieces | Avg piece weight | Picks per ton |
|---|---|---|---|---|
| Warehouse with heavy girders | 180 | 220 | 1,636 lb | 1.2 |
| Typical low-rise office | 180 | 380 | 947 lb | 2.1 |
| School with lots of infill and misc | 180 | 600 | 600 lb | 3.3 |
The school has almost three times the picks of the warehouse for the same steel weight. If your historical $/ton number came from warehouse-type jobs, it'll be badly short on the school. Our steel erection cost per ton guide gives the per-ton ranges by project type; this post is about checking those ranges against the piece count before you send the number.
If you'd rather not count members off the plans by hand, upload the drawing set to SteelFlo. Every member is a box on the sheet, so the piece count you bid from is one you can check line by line. The first 3 takeoffs are free.
How many pieces per day can an erection crew set?
A conventional raising gang is usually a foreman, crane operator, two connectors, a hooker-on or signal person, and sometimes an oiler on bigger cranes. Behind them, a bolt-up and plumbing crew follows. Typical production for the raising gang, assuming a decent laydown area and steel that shows up in sequence:
| Member type | Typical pieces per 8-hr shift | What slows it down |
|---|---|---|
| Light infill beams (W8 to W12), short spans | 35 to 50 | Lots of small connections, frequent crane swings |
| Typical floor beams and girders (W14 to W21) | 25 to 40 | Double connections at girders, deck bundles in the way |
| Columns, single-tier | 12 to 25 | Anchor rod setting, guying, plumbing |
| Heavy girders and transfer members | 8 to 20 | Rigging changes, larger crane setups |
| Open web joists (hoisted individually) | 40 to 70 | Bridging must go in before workers are released onto them |
| Moment-frame members | 10 to 20 | Full-pen field welds or heavy bolted flange plates |
These are planning ranges, not guarantees. Site access, crane position, weather, and how well the fabricator ships in sequence matter more than any table. Track your own crews by member type and you'll have numbers better than any published average.
Multiple-lift rigging (Christmas-treeing) can raise the count on light beams. OSHA allows up to five members per lift under the multiple lift rule in 1926.753, with specific rigging and training conditions. Don't assume it on every job. Plenty of GCs and site safety plans restrict it.
How do you get from piece count to crew and crane days?
The core formula is simple:
Raising days = pieces ÷ pieces per day (by member type)
Then add the parts that don't scale with picks:
- Mobilization and crane setup. Assembly of a crawler can eat one or two days before the first pick. A truck crane might be a few hours.
- Crane moves. Each relocation on a building that's too big to reach from one spot costs half a day or more.
- Bolt-up and plumbing. Usually a separate crew working a day or two behind the raising gang.
- Deck and detailing. Decking, shear studs if the erector carries them, and punch-list work at the end.
Break the takeoff into member groups before you divide, because one blended pieces-per-day number hides the slow stuff. Fifty columns at 15 a day is a little over three days. Four hundred infill beams at 40 a day is ten. If you average those as "450 pieces at 30 a day" you get 15 days and won't know where the risk sits.
How do connections, bolts and deck add hidden time?
Picks are only half the labor. Every piece has at least two ends, and every end is a connection that needs to be bolted up, snugged, and often pretensioned and inspected.
A rough connection count from a takeoff:
Connections ≈ beams × 2 + columns × (splices + base)
Then:
Field bolts ≈ connections × average bolts per connection
Simple shear tabs and double angles on light beams might average 3 or 4 bolts. Girder-to-column connections and moment connections can run 8 to 20 or more. If you have a bolt list from the connection design or shop drawings, use it. If you're bidding off contract drawings, the connection cost guide covers typical connection types and what they cost, and the post on finding bolts on steel drawings explains where bolt callouts usually hide.
Bolt-up productivity varies a lot with bolt size, access, and the tensioning method (turn-of-nut, twist-off tension-control bolts, or direct tension indicators). Get your crew's real numbers. For planning, a two-person bolt-up crew working at reachable connections often lands somewhere in the low hundreds of bolts per day for installation and snugging, with pretensioning and inspection added on top.
Deck is its own takeoff. Bundle landing, spreading, and fastening run on square feet, not pieces. The metal deck takeoff guide walks through it.
Which OSHA Subpart R items affect erection productivity?
OSHA 1926 Subpart R is the federal steel erection standard. You don't bid compliance as a line item, but several provisions directly set the pace, so build them into your crew days:
| Provision | What it requires | Effect on the schedule |
|---|---|---|
| 1926.752 Site layout and approval to begin | Written notice that concrete in footings and walls has reached 75% of design strength (or enough to carry erection loads), plus adequate access and a firm, drained laydown area | Erection can't start until the GC provides it. A late notice idles your crew |
| 1926.753 Hoisting and rigging | Pre-shift crane inspection by a competent person; multiple lift limits | Fifteen to thirty minutes at the start of every shift |
| 1926.755 Column anchorage | Minimum of 4 anchor rods per column | Anchor rod problems (wrong projection, out of position) stop column setting |
| 1926.756 Beams and columns | At least two bolts per connection, wrench-tight, before releasing the hoisting line; rules for double connections | Sets the minimum connector time per pick |
| 1926.760 Fall protection | Protection above 15 ft generally; connectors above two stories or 30 ft; controlled decking zones limited to 90 x 90 ft and 3,000 sf of unsecured deck | Affects how fast deck can lead the frame and how many tie-off points you need |
The Steel Erectors Association of America publishes safety flashes and training resources that are worth reading before you set productivity assumptions for a new crew or a new kind of work. And check the contract: AISC 303, the Code of Standard Practice, defines who's responsible for things like anchor rod placement and erection bracing unless the contract says otherwise.
Worked example: 600 pieces, 180 tons
Here's a three-story school, 180 tons of structural steel. Price it two ways. All rates below are illustrative assumptions for the math, not market quotes. Plug in your own.
Assumptions:
- Raising gang of 6 at $95/hr all-in, 8-hr shifts: $4,560/day
- 90-ton hydraulic crane, bare rental at $2,200/day (operator is counted in the gang)
- Bolt-up crew of 2 at $95/hr: $1,520/day, averaging 300 bolts/day installed and snugged
- Per-ton benchmark the estimator usually uses for low-rise: $550/ton
Per-ton price: 180 × $550 = $99,000
Piece-count build-up from the takeoff:
| Member group | Pieces | Pieces/day | Raising days |
|---|---|---|---|
| Columns (W10, W12) | 64 | 16 | 4.0 |
| Girders (W18 to W24) | 96 | 28 | 3.4 |
| Floor and roof beams (W12 to W16) | 260 | 38 | 6.8 |
| Infill, lintels, misc framing | 180 | 45 | 4.0 |
| Total | 600 | 18.2, call it 19 |
Raising cost: 19 days × ($4,560 + $2,200) = $128,440
Connections: about 536 beams × 2 ends + 64 column bases = 1,136 connections. At an average of 4 bolts each, roughly 4,500 field bolts. At 300 bolts a day, that's 15 bolt-up days × $1,520 = $22,800.
Add 2 days for mobilization, setup and one crane move at $6,760/day = $13,520.
Piece-count total: about $164,760, or $915/ton.
That's two-thirds more than the per-ton price. Now run the same math on the warehouse from the first table, 180 tons in 220 pieces at heavier weights. At around 25 pieces a day you're near 9 raising days, roughly 440 connections, and about 2,600 bolts at 6 per connection. The total comes out somewhere near $90,000, or $500/ton. The per-ton benchmark is close on the warehouse and badly wrong on the school.
That's the whole argument. A per-ton rate is an average of jobs you've already done. It's only accurate when the new job has a similar piece weight. Check picks per ton (pieces ÷ tons) on every bid. If it's well above your historical average, build the price up from pieces.
On multi-level buildings, also split pieces by floor, because the top floors usually mean longer picks and more crane moves. The multi-story frame estimating guide covers sequencing by level.
Where do you get a reliable piece count?
There are three usual sources, in order of how much you can trust them:
- Erection drawings or an advance bill from the fabricator. Best source, but often not available at bid time.
- Your own takeoff from the contract drawings. Count every beam, column, brace, and misc piece on every sheet. It's slow, and it's easy to double count members shown on both an enlarged plan and the overall plan.
- A tonnage figure from the GC or fabricator, divided by a guessed average weight. Fast and unreliable. This is exactly the shortcut that loses money on light jobs.
If you're doing option 2, a takeoff tool that ties each counted piece to its spot on the drawing makes the count auditable. You can look at any line and see where it came from. That's how SteelFlo's estimating software works: each member label on the drawings gets its own box, you confirm or reject them, and the count is the number of confirmed boxes. Then "Price This" lets you apply your own erection rates.
Frequently Asked Questions
How many pieces of steel can an erection crew set in a day?
A typical raising gang sets about 25 to 40 pieces per 8-hour shift on conventional low-rise framing. Light infill beams can run 35 to 50, while columns and heavy girders often drop to 10 to 25. Track your own crews by member type for the most reliable numbers.
Should steel erection be priced per ton or per piece?
Use both, and trust pieces when they disagree. A per-ton rate works when a job's average piece weight matches your past work. On light, many-piece jobs, build the price from pieces per day, connections, and crane days, then compare it to your per-ton benchmark.
How do I estimate crane days for steel erection?
Divide the piece count for each member group by realistic pieces per day, add them up, then add mobilization, crane assembly and any crane moves. Crane size comes from the heaviest pick at its radius, which is where tonnage and piece weight actually matter.
How do OSHA rules affect steel erection productivity?
Subpart R sets minimums that limit how fast connectors can work. For example, it requires two wrench-tight bolts per connection before the crane releases a member, and it limits controlled decking zones. Late concrete-strength notice from the GC can also delay the start. Build these into your crew days rather than treating them as exceptions.
What is a good picks-per-ton ratio?
There's no universal number, but heavy industrial and warehouse jobs often run near 1 pick per ton, while schools and offices with lots of infill can run 2 to 4. Compare each bid to your own historical ratio. A big jump is a signal to build up erection from pieces.
Bottom line
Tons tell you which crane to bring. Pieces and connections tell you how long you'll keep it. Get an honest piece count by member type, divide by your crew's real production, add bolts and crane moves, and check the result against your $/ton number before you bid. If counting is the bottleneck, run the drawings through SteelFlo and spend your time on the production rates instead.