Concrete Column Repairs, Barn near Denmead

The problem

A landowner came directly to us about 4 concrete columns on a barn near Denmead, spalling with corroding rebar visible where it had pushed the concrete apart. Repair areas were generally 500mm to 1 metre tall per column.

The cause

Agricultural buildings of this age were often built with less concrete cover protecting the steel than modern standards require, giving moisture an easier route to the reinforcement. Once the steel corrodes and expands, it pushes the surrounding concrete apart from the inside.

What we did

1. Steel treatment. Exposed reinforcement treated with Fosroc Nitoprime Zincrich primer to stop the corrosion before any mortar was applied.
2. First coat of Fosroc Renderoc. The repair mortar was applied in the first hit on day one. Due to the temperature at the time, it wasn’t possible to build the product up to full depth in one application — doing so would have risked the mortar not curing properly.
3. Second coat and finish. The second coat was applied on day two once the first had cured, bringing the repair up to full depth and finishing to match the original column profile. Fosroc products were chosen for ease of finishing and strength once set.

The result

Completed over 2 days by one person. The two-coat approach was dictated by temperature conditions on site — applying too much repair mortar in one go in cold weather risks poor curing and a repair that fails early. Recognising that and splitting the application was the right call for a durable result.