Concrete Crack Repair & Water Ingress in Sydney

What concrete cancer repair in Sydney actually involves

Not every crack is concrete cancer. Shrinkage cracking in a slab is common and often harmless; a crack that is leaking, staining or lifting the surface next to it is a different matter. The pattern worth acting on is a crack with rust colour coming out of it, or white crusty deposits along it — efflorescence, which is salts carried out of the concrete by water moving through it.

Finding the route the water takes

On balconies the usual route is a waterproof membrane that has reached the end of its life under a tiled surface. Water gets past the tiles, sits on a membrane that no longer sheds it, finds the slab edge or a penetration, and works its way to the reinforcement. Lifting a corner of the covering is often how it is confirmed. The fix is a membrane and a fall that actually drains, not a sealant along the crack.

Where a repair has already been done and the water was not addressed, the same bar corrodes behind the new mortar and the repair fails at its edges. This is the most common reason a building has two generations of patch on the same balcony — the second one done because the first one was only ever half the job.

Concrete Crack Repair & Water Ingress in Sydney — common questions

Is efflorescence a problem in itself?

The white deposit is not damaging on its own — it is a symptom. The thing to follow is where the water is coming from, rather than scrubbing the deposit off.

Can the membrane be replaced without lifting the tiles?

Generally not, if the membrane is under them. A liquid-applied membrane over the top of an existing tiled surface is sometimes offered; whether it is appropriate depends on what is underneath and where the water is currently going, which is an inspection question rather than a product question.

The balcony was repaired a few years ago and it is spalling again — why?

Most often because the water was never addressed. A repair that treats the concrete but leaves the membrane, the fall or the drainage as they were puts the same bar back in the same conditions.