Rust and crack formation on facades

When determining the probable cause of crack formation, we may be dealing with a stable crack ; damage that has not developed further (caused by shrinkage and creep) or an unstable crack ; damage that is developing further (e.g., due to foundation subsidence). In these cases, the cause must first be eliminated before a proper repair can be carried out.

Rust formation occurs mainly in the following types of ironwork:

• Balkan anchors, blind anchors, sheet anchors and ornamental anchors
• Cavity wall ties
• Fencing (balcony railings, access gates, etc.)
• U- and I-shaped beams (as lintel or part of floor structures)

Anchors are often affected by the oxidation process . The corrosion products expand significantly; rusting iron can result in a six- to eight-fold increase in the volume of iron material! If this expansion is prevented, the surrounding masonry exerts forces on the masonry that are so great that it cracks or shatters in places.

Damp conditions in and around walls often cause rust. The damage is often extensive with anchors that don't penetrate the walls, but are incorporated into them to absorb and transfer forces from vaults, for example. If the anchors in the walls are exposed to damp conditions, oxidation occurs, posing a risk of collapse in the long term, while significant damage to the masonry can occur in the short term.

Anchors must be removed, replaced with new ones, or derusted, for example, by sandblasting. Furthermore, the anchors must be protected, for example, by hot-dip galvanizing, after which they can be reinstalled and reworked.

In addition, measures can be taken to improve the conditions in which anchors are located, such as preventing or reducing any moisture ingress into the wall (for example, repairing a leaking gutter).