Anchoring and wall ties

A scaffold is tall and narrow and would topple from wind and uneven loads if it stood free. The anchorage transfers the horizontal forces to the building and holds the scaffold in against the facade. It takes both tension (wind sucking the scaffold away) and compression (wind pushing it in).

The anchor must suit what it is fixed into: an eye bolt in a drilled-in plug in masonry/concrete, through anchors, or anchoring around a fixed part of the building with anchor tubes and couplers. The facade's material and strength determine what can bear the load — and the actual tensile capacity per anchor (R_anker) is stated in the supplier's data sheet; it is not guessed.

An anchor's capacity is only as good as what it is fixed into — check the strength of the facade.

The number of anchors and their pattern (horizontal and vertical spacing, whether every node or every second node is anchored) is a design matter shown on the scaffold drawing and in the supplier's assembly instructions. Follow the plan — never reduce or move anchors on your own initiative.

Outdoor scaffolding over 10.5 m must be anchored. The anchors are fitted PROGRESSIVELY as the scaffold is built upwards — it must never stand free at full height waiting for anchoring. Low facade scaffolding within the stability limit may in certain cases stand without anchors, but this is decided by the design.

Wind is the major load on a scaffold. The horizontal wind load depends on the degree of cladding: an open scaffold catches far less wind than a clad one. The scaffold calculator uses guideline cladding factors φ of approx. 0.35 for open, 0.50 for netting and 1.00 for sheeting — the actual peak velocity pressure is calculated according to DS/EN 1991-1-4 DK NA.

Netting and especially sheeting turn the scaffold into a sail: the wind load — and thus the anchoring forces — increase significantly. If an existing scaffold is to be enclosed, the stability and anchor plan must be recalculated; you cannot just hang sheeting on a scaffold designed as open.

Tarpaulin ≈ full sail. Never sheet a scaffold without recalculating the anchorage.

Retighten all anchors and couplers, and check that there is no movement at the anchor points. A coupler fitted by hand (a clamp) instead of being properly bolted can slip under load. The anchor points are part of the routine inspection — check them after strong winds.

Retighten all couplers and check the anti-rotation lock — an anchor that can slip is no anchor.

If an anchor cannot be placed where the plan requires it (window, movement joint, thin material), the anchor plan must be redesigned — typically with extra anchors at neighbouring points to compensate for the missing anchorage. Omitting anchors on one or two levels without compensation weakens the stability of the entire structure.