What is a 30 percent or 60 percent drawing set?
A 30 or 60 percent set is a construction document issue the design team labels with its own estimate of completeness. At 30 percent expect missing column schedules and unsized members; at 60 the frame is mostly real but connections and misc steel are not. Steel bid off these sets gets re-estimated when the finished design lands.
Key facts
- The percentage is the design team's own estimate of completeness, not a measured quantity. A 60 percent set is a statement of intent, not a promise.
- There is no single ladder. Some offices treat 30, 60, and 90 as thirds of the construction documents; others map 30 to schematic and 60 to design development. The label means what the issuing office says it means.
- Owners bid steel early, off 30 or 60 percent sets, to lock fabrication capacity and mill slots before the design is finished. The stamp on that early bid set is often IFB, issued for bid, not a percentage at all.
- At 30 percent, expect missing column schedules, unsized members, and details that do not exist yet. At 60, the frame is usually real but connections and misc steel are not.
- The risk is not the missing information. It is that the finished design arrives later as a full new set, and the difference is your problem to find.
What does each stage actually contain?
A 30 percent structural set usually has grids, typical bays, preliminary member sizes on the main framing, and a structural narrative describing what is not drawn yet. Column schedules are often absent or placeholder. A 60 percent set generally has real member sizes, a usable column schedule, and most typical details, with connections still delegated and miscellaneous steel thin. By 90 percent the set should read like a buildable job with loose ends. The IFC issue is the one you build from.
Offices differ, and the percentage is self-reported. The estimators we talk to have received 60 percent sets that were honest 40s. Read the set, not the label.
The rough equivalences, and they are rough, run like this:
| Label | Often corresponds to | Structural reality to expect |
|---|---|---|
| 30 percent | Schematic design, or an early third of the CDs | Grids, typical bays, preliminary sizes, narrative |
| 60 percent | Design development, or mid-CDs | Real sizes, usable column schedule, connections delegated |
| 90 percent | The CD or bid set | Buildable with loose ends |
| IFB | Issued for bid, at whatever completeness the owner chose | The set most steel bids actually price |
| IFC | Issued for construction | The set you build from |
The IFB row is the one that matters commercially: the stamp family around IFC is what the title block actually says, and an IFB set can land anywhere on the percentage ladder.
How do you bid off an early set?
Price what is drawn, state what is assumed, and qualify the rest. The bid names the set and date it priced, carries an allowance or exclusion for connections and misc steel if they are not designed, and flags the missing schedule if there is one. The alternative, silently guessing the missing scope, converts design risk into your margin.
Then treat the next issue as a comparison job, not a new job. When the finished design lands, the question that matters is what changed against the set you priced, member by member. Answering it from scratch is a full re-estimate. Answering it from a revision comparison is a review.
Example
A shop bids a warehouse off a 60 percent set dated April 2, qualified to that set and date, with connections carried as an allowance and misc steel excluded. The IFC set lands June 9: the W14 roof columns grew a size, forty connections now exist on paper, and a mezzanine appeared. Because the bid named its set, the comparison against the April takeoff is the change list, and the mezzanine is priced as added scope instead of argued about. The shop that bid the same job unqualified is having a different June.
How Ferra handles this
Ferra takes off whatever exists at 30 or 60 percent, and when the next issue arrives it compares the sets and lists the changes, so an early-set bid does not commit you to re-estimating the job from zero. See Revision Control.
Sources
- AISC 303, Code of Standard Practice for Steel Buildings and Bridges, for the principle that the fabricator's scope is what the contract documents show, which is what a qualification on an incomplete set protects.
- Set-quality patterns as reported by the estimators we talk to, stated without attribution.