Steel Frame Erection Tolerances: Plumb, Level and Alignment

Steel frame erection tolerances are the permitted errors in the position of the erected steel: how far a column may lean, how far a beam may be off level and how far a line of members may drift. They are different from fabrication tolerances, which cover each piece in the shop. Both are needed for a frame that fits and performs as designed.

Why erection tolerances matter

Cladding, doors, cranes and equipment all rely on the frame being where the drawing says it is. A leaning column, a sagging line of beams or a crane rail out of line causes problems that are expensive to fix after the roof is on. The idea of a permitted error is explained in this note on engineering tolerance.

What is checked

• Plumb. How far columns lean from vertical, along their height.
• Level. The height of beams, base plates and crane rails.
• Alignment. The position of columns and members along the grid lines.
• Spacing. The distance between frames, which sets the bay size.
• Straightness. Of columns and rafters after erection.

The limits come from the project specification or the standard it refers to. Do not copy a number from another project.

Steel frame erection tolerances in sequence

Checks should follow the erection sequence, not wait for the end. Check the base plates and anchor bolts before the steel arrives, as explained in anchor bolts and base plates. Check each bay for plumb and line before the crane moves on, and record the readings. Our guide to erection sequence and temporary stability shows when bracing allows safe adjustment.

How errors are corrected

Small errors are corrected with shims, packing or by adjusting the temporary bracing before bolts are fully tightened. Larger errors need an engineering decision. Enlarging holes or forcing members into place can weaken the connection. The order of tightening also matters, as described in bolt tightening methods for structural steel.

Fabrication affects erection

Accurate fabrication is the first defence against erection errors. Members that are the right length with holes in the right place go up with few corrections. Our guide to steel column fabrication tolerances covers the shop side, and marking and packing help the crew place each member correctly, as in steel member marking and packing lists.

Surveying and records

Use a total station or level to survey the frame at agreed points, and record the results with the date and the weather. Temperature can move a long frame, so note it when measuring. Keep the survey with the handover pack, as it supports later modifications and any claim.

Responsibility

The contract decides who is responsible for each tolerance. When one steel structure contractor carries fabrication and erection, the responsibility is simple. When scopes are split, define who surveys the foundations, who sets out the grid and who accepts the frame. Our guide to what a steel structure contractor provides explains the usual splits.

Checklist

1. Tolerance limits named in the specification
2. Survey points and times agreed
3. Foundations and anchor bolts surveyed before steel arrives
4. Each bay checked before the crane moves on
5. Corrections approved by the engineer where needed
6. Final survey recorded

If you need an erection tolerance plan for a project, contact the engineering team and send the drawings and the specification.

Frequently Asked Questions