Steel corrosion investigation and rectification

Understanding steel corrosion in buildings

Steel corrodes where its protective coating or galvanising has broken down and moisture and oxygen reach the metal, a process accelerated near the coast and wherever water is trapped against the steel. Rust occupies several times the volume of the steel it replaces, so it cracks the concrete, masonry or render around embedded members and jacks apart bolted connections.

Typical locations include lintels over openings, awning and canopy supports, balustrade posts set into balconies and stairs, exposed roof and plant framing, fire-stair stringers and the fixings that hold cladding and services. This page concerns the steel itself; corrosion of reinforcement inside concrete is addressed under concrete spalling.

How the steelwork is assessed and scoped

DYME coordinates inspection with the structural engineer so that the remaining section of each affected member is assessed, not just its appearance. Where members are concealed or embedded, localised openings are made to expose the connection or base. Accessible members are cleaned back to sound metal where needed to establish the extent of loss.

The scope sets out, member by member, whether the steel is to be cleaned and recoated, strengthened, or cut out and replaced, and the protective system to be applied. Temporary propping or restraint during replacement is designed where the member is carrying load.

How rectification is delivered

Load-bearing members are addressed first under the engineer’s direction, with temporary works installed before any cutting begins. Fabricated replacement sections are procured early, and surface preparation and coating are carried out to the specification with inspection points before encasement or closing up. Masonry, render and finishes around the repaired steel are reinstated afterwards.

Works to awnings, balustrades and roof framing are planned around public and resident safety, with exclusion zones and access control. For a Sydney or NSW steel corrosion enquiry, provide the building location, which elements are affected, any engineer’s report, photographs, access considerations, budget range and required timeframe.

Common questions

Can corroded steel be treated rather than replaced?

Where section loss is minor, cleaning back to sound metal and applying a suitable protective system is often appropriate. Where the engineer assesses the loss as significant, strengthening or replacement is specified instead.

Is the building safe while the steel is being replaced?

Load-bearing members are replaced under temporary propping or restraint designed by the engineer, and public or resident areas below are closed or protected for the duration of that activity.

How is this different from concrete cancer?

Concrete cancer is corrosion of the reinforcing bars inside concrete and is repaired through the concrete. This scope addresses structural and architectural steel components, which are repaired, strengthened or replaced as members in their own right.