Direct Answer
AISC Code of Standard Practice Chapter 7 defines erection tolerances: columns must be plumb within 1:500 of true vertical, beam seats and connections must be within ±3/8" of theoretical position, and multi-story columns may accumulate no more than 1" of total drift from plumb over the full building height. These tolerances govern when erection work is accepted.
Full Explanation
Key AISC erection tolerances: (1) Column plumbness: maximum out-of-plumb = lesser of 1/500 of height or 1" for tier columns. (2) Column alignment: column web and flange must be within 1/4" of theoretical position at each tier. (3) Beam ends: ±3/8" from theoretical position in plan, ±3/8" in elevation. (4) Total cumulative plumb drift: buildings over 300 feet must not accumulate more than 1" total column drift from plumb. These tolerances stack with fabrication tolerances — the system tolerance is the sum of the fabrication and erection tolerance contributions.
What This Means for Your Shop
As a fabricator, your responsibility ends at shipping members within AISC fabrication tolerances. The erection contractor is responsible for meeting erection tolerances. However, fabrication errors that are at the tolerance limit can make it impossible for the erection contractor to meet their tolerances — communication between fabricator and erector about actual dimensions helps both parties succeed.
Common Mistakes
Accepting a column that is at the fabrication tolerance limit and shipping it without notifying the erector. A column that is 3/4" off plumb due to fabrication (at the tolerance limit for a 12-story column) leaves no margin for erection adjustment.
Recommended Process
For columns in tall or complex structures, measure actual dimensions at key points and share them with the erection contractor before shipping. This allows the erector to pre-plan adjustments and reduces field surprises.