Before anything falls
The cover has already separated from the steel. It has simply not fallen yet, and that is the window worth using.
Drummy is the trade word for concrete that sounds hollow when tapped. Concrete Cancer Brisbane arranges the survey that maps it, and on most buildings the drummy area is two to three times what is visibly damaged.
Sound concrete bonded to its reinforcement rings when struck. Concrete that has been pushed away from the steel by expanding rust has a void behind it, and a void changes the note to a hollow, dead knock. The difference is obvious once you have heard both, which is why a hammer tap survey is a genuinely reliable method and not a crude one.
Drummy concrete is spalling that has not happened yet. It will fall — the only question is when, and whether anything is underneath. This is exactly why an inspection maps the drummy extent rather than photographing the visible damage: the budget has to cover what will need repairing, not what currently looks bad.
It is also the single most common source of variations. A committee that approves a contract priced from visible damage will meet the rest of it as a variation once the contractor starts tapping, and by then there is no competitive tension left.
Where drummy concrete is over a walkway, a parking bay, a footpath or a balcony below, the sensible immediate step is to isolate the area or have the loose material taken down under control, rather than programming it for the next budget cycle. That is a separate and much smaller job than the repair, and it changes the risk position immediately.
Most of the stock affected is the 1960s–80s walk-up belt and the bayside strip, where salt air reaches the steel faster.
Tell us what the concrete is doing. We will arrange an inspection and a written scope your committee can actually price.
