The short answer
Column plumbness and base elevation matter most, because every mechanical package above inherits them. A structure erected out of plumb cannot be corrected once equipment is landed on it.
Structural steel is the datum for everything above it. Deviation here is not absorbed — it is inherited by every mechanical package that follows.
Check the foundation before you lift
Anchor bolt position, projection and base plate elevation should be surveyed and accepted before the first column goes up. Discovering a bolt group is out of position with three columns already standing is an expensive way to learn this.
The measurements that govern
| Item | Why it matters | When to check |
|---|---|---|
| Base elevation | Sets every level above | Before erection |
| Column plumbness | Equipment alignment inherits it | Before final bolting |
| Beam level | Grating and equipment seating | Per level, as erected |
| Bay dimensions | Equipment will not fit if wrong | Before releasing the bay |
| Bolt torque | Joint capacity | Progressively, recorded |
Bolt up in the right order
- Erect and temporarily bolt, keeping the frame adjustable
- Plumb and align the bay as a whole, not column by column
- Only then torque to final value and mark each bolt
- Record torque on a marked-up drawing as you go
Survey and record
A total station survey per level, recorded and issued, costs very little and settles disputes before they become commercial. It also gives the mechanical team a real datum rather than an assumption.
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