Erection sequence

The state during erection

The stability of the finished structure comes from the bracing, the lining and the connections together. During erection some of them are still missing.

So the state during erection is a separate load case:

• the frame stands with less restraint,
• the wind already acts in full,
• and lifting and handling load it too.

Temporary bracing

Not optional. Where the permanent bracing is not yet complete, temporary bracing is needed — and it can only be removed as erection progresses.

That is especially true for:

• trusses, which are unstable out of plane,
• tall wall panels before lining,
• long, narrow parts of the building.

The typical sequence

1. Survey and level the foundation. Setting out and foundation tolerances.
2. Place the bottom tracks, with damp-proofing.
3. Stand the wall panels, with temporary bracing.
4. Install the hold-downs and the permanent bracing.
5. The floor structure.
6. The next storey, the same way.
7. The roof structure.
8. The linings that provide the permanent bracing.

At every step there is a point at which the structure is not yet final — there the temporary solution holds it.

What the design has to contain

• the logic of the erection sequence,
• the position and method of the temporary bracing where it is critical,
• the lifting points for a panelised structure,
• the manufacturing and delivery sequence, so the members arrive in erection order.

That last detail is often overlooked, yet on a tight site it decides whether things have to be double-handled.

The timing of inspection

Erection is the time when the structure is still visible. The bracing, the screw fixing and the anchorage can be checked then — not once the lining is on. Inspection points.

The point

The frame is weaker during erection than when finished. Temporary bracing is not over-caution but part of the structure until the permanent bracing is done.