Division 5 is the CSI MasterFormat division covering all metals on a project. Structural fabricators typically bid 05 12 00 (structural steel framing) and sometimes 05 21 00 (joists) and 05 31 00 (deck), while 05 50 00 metal fabrications — stairs, railings, lintels, embeds — is where scope gaps live. Most bid disputes trace to the 05 12 00 / 05 50 00 boundary.
If you've ever eaten the cost of 40 loose lintels because "it's steel, so it's yours," this post is the fix. Division 5 looks tidy on paper. On real bid packages, the section numbers get ignored, the specs contradict the drawings, and the GC assumes the structural fabricator covers everything with iron in it.
What is Division 5 in CSI MasterFormat?
MasterFormat, published by the Construction Specifications Institute, organizes specifications into 50 divisions. Division 5 — Metals — covers everything from the building frame down to a decorative handrail bracket. The sections you'll actually meet on commercial work:
| Section | Title | Who usually bids it |
|---|---|---|
| 05 05 00 | Common Work Results for Metals | Reference only (welding, coatings, fasteners) |
| 05 12 00 | Structural Steel Framing | Structural fabricator |
| 05 21 00 | Steel Joist Framing | Joist supplier via fabricator or GC |
| 05 31 00 | Steel Decking | Deck supplier / erector, often through the fabricator |
| 05 40 00 | Cold-Formed Metal Framing | Drywall/framing sub, not the structural fab |
| 05 50 00 | Metal Fabrications | Misc metals shop — or nobody, which is the problem |
| 05 51 00 | Metal Stairs | Misc metals shop or structural fab |
| 05 52 00 | Metal Railings | Misc metals shop |
| 05 53 00 | Metal Gratings | Misc metals shop |
| 05 70 00 | Decorative Metal | Ornamental shop |
The spec book will list which sections exist on the project. Read that list before you read anything else — a project with a 05 50 00 section has misc metals scoped somewhere; a project without one has misc metals scoped nowhere, and the GC will try to put it in your number.
What does 05 12 00 structural steel actually include?
The core of a structural fabricator's bid. In a typical 05 12 00 spec you own:
- Wide-flange beams and columns, HSS, channels, angles that are part of the frame
- Base plates, cap plates, stiffeners, and shear/moment connections
- Anchor rods (supply — setting them is usually the concrete sub)
- Shop primer per the spec, and often shop drawings and erection
What 05 12 00 usually does not include, even though it's steel: loose lintels over masonry openings, embed plates cast into concrete, elevator hoist beams and divider beams, dunnage and equipment frames, bollards, ladders, and anything the architect drew instead of the engineer. Those live in 05 50 00 — in theory.
The AISC Code of Standard Practice has its own definition of "structural steel" in Section 2, and it's narrower than what GCs assume. Lintels attached to the frame are structural steel under the COSP; loose lintels shipped to the mason are not. That one distinction is worth reading the section for.
Which Division 5 sections should a structural fabricator bid?
The pattern that keeps margins intact at most small and mid-size shops:
- Always bid: 05 12 00. That's the business.
- Bid if you buy well: 05 21 00 joists and 05 31 00 deck. You're brokering a joist and deck package with markup and coordination risk. Plenty of fabricators include it because GCs want one throat to choke for the frame; price the coordination time, not just the vendor quote. On big-box work the joist/deck package can be half the contract value, so treat the vendor quote's own exclusions as part of your scope math.
- Bid selectively: 05 51 00 stairs and 05 52 00 railings — only if your shop actually does stairs profitably. Stairs are detail-hour black holes; a stair tower can carry more shop hours than 20 tons of beams. Our stairs and railings takeoff guide covers the unit pricing.
- Exclude by default: 05 40 00 cold-formed framing (that's the drywall sub's world — see the cold-formed SSMA takeoff guide), 05 70 00 decorative metal, and gratings unless they're on your dunnage.
Whatever you decide, say it in writing. A one-page inclusions/exclusions list — a real scope letter — is the cheapest insurance in this industry.
Where do scope gaps happen between 05 12 00 and 05 50 00?
The classic traps, in rough order of how often they cost money:
| Item | Where it's drawn | Where GCs assume it lives | Reality |
|---|---|---|---|
| Loose lintels | Architectural sheets, lintel schedule | Your bid | 05 50 00 — exclude or price separately |
| Embed plates | Structural sheets, concrete details | Your bid | Supply often yours, install is concrete sub's |
| Elevator hoist beams | Architectural / elevator drawings | Nobody's bid | Explicitly include or exclude |
| Roof frames and dunnage | Mechanical sheets | Nobody's bid | RFI it — mechanical steel is a change-order factory |
| Stair pans and rails | Architectural sheets | Your bid | 05 51 00 / 05 52 00 — separate line or exclusion |
| Bollards, gate posts | Civil/site sheets | Nobody's bid | Exclude by default |
Two structural things make these traps dangerous. First, the items are scattered across architectural, mechanical, and civil sheets that a structural estimator may never open — a lintel schedule buried on A-501 can carry three tons of angles. Second, "steel" in a GC's mind is one trade. If your bid is silent, silence reads as inclusion. The fabricators who win at this game bid 05 12 00 tight, list every 05 50 00 item they saw as a separate add-price, and exclude the rest by name.
How do you take off Division 5 scope without missing pieces?
Run the takeoff by section, not by sheet. Count the 05 12 00 frame off the S-sheets first, then do a second deliberate pass through the architectural set hunting misc metals — lintel schedules, stair sections, railing elevations, embed details. Keep the two counts in separate line items so you can quote them separately. The steel estimating checklist covers the full pre-bid sweep.
This is where software earns its keep on multi-discipline sets. SteelFlo reads the full PDF set — structural and architectural pages alike — finds every steel member label on every page, and draws a bounding box around each one for you to verify, so a lintel called out on an architectural sheet gets counted the same way a W12X26 on S-201 does. The count is the number of boxes: no inference, no hidden math, and each detection is verifiable against the drawing before it hits your BOM. With AI detection plus human verification, accuracy runs 95–99%, and the section library covers 4,500+ sections across 6 standards.
However you count it, the output should be a clean bill of materials split by spec section — because that's how the GC's buyout spreadsheet is organized, and matching their structure is how your exclusions actually get read.
Quick answers
What is Division 5 in construction? The CSI MasterFormat division for metals: structural steel (05 12 00), joists (05 21 00), deck (05 31 00), cold-formed framing (05 40 00), and metal fabrications including stairs and railings (05 50 00 series).
What's the difference between 05 12 00 and 05 50 00? 05 12 00 is the structural frame — beams, columns, frame connections. 05 50 00 is miscellaneous metal fabrications — loose lintels, ladders, embeds, stairs, railings — usually a different shop and always a different risk profile.
Do structural fabricators bid metal fabrications? Some do, most shouldn't by default. Bid 05 50 00 items as separately priced adds with their own line items, or exclude them by name in the scope letter.
Are loose lintels structural steel? Under the AISC Code of Standard Practice, lintels attached to the structural frame are structural steel; loose lintels set by the mason are not. Price them as a separate line either way.
Counting a Division 5 package this week? Run the drawings through SteelFlo's takeoff — every member label found and boxed for verification, structural and architectural sheets alike — or check section weights fast with the free calculator and the shape database.