Retaining Wall Repairs & Drainage In Wollongong

In most cases it is trapped water. When the soil behind a wall saturates and cannot drain, it builds hydrostatic pressure that pushes against the wall with more load than it was built to carry, and the wall responds by leaning, bulging, cracking or slumping. Poor or missing drainage is the number-one cause of retaining-wall failure. In the Illawarra it is made worse by high rainfall, runoff coming off the escarpment, and reactive clay soils that move with the wet and dry. Undersized walls or walls built without proper footings can also move, which is why we diagnose the real cause before quoting a fix.

It depends on why it failed and how far it has gone, and we will tell you honestly. If the structure is basically sound but the drainage was missing or has clogged, we can often rectify the wall and retrofit proper drainage. If the wall is badly bulged, undersized, or was built without adequate footings or engineering for the load it carries, rebuilding the failed section to a sound, drained and where needed certified design is the honest fix rather than a patch that will move again. We assess the drainage, the footings and the wall's design at a free on-site visit, then recommend the option that actually solves the problem.

We retrofit the drainage system that most failed walls were missing. That means excavating behind the wall, installing an agricultural drain along the base to collect and carry water away, backfilling with free-draining aggregate so water moves down to the drain instead of pooling, wrapping the aggregate in geofabric so soil fines cannot clog it, and adding weep holes through the face to release any remaining water. Done properly this manages the hydrostatic pressure that caused the failure. On Illawarra blocks catching escarpment runoff it is the single most important part of the repair, and it is exactly what tends to get skipped on a cheap original build.

It is worth acting sooner rather than later. A retaining wall rarely fixes itself, and a slow lean or a small bulge can become a sudden collapse after heavy rain, which is a genuine risk in the wet Illawarra climate, and far more expensive and dangerous than an early repair. If the wall retains a driveway, a structure or a neighbour's ground, or if people pass close to it, the risk is higher again. We are not trying to alarm you, but if you can see clear leaning, bulging, stair-step cracking or sleepers pushing out, it is sensible to get it assessed before the next big downpour rather than after.

It can, on the same basis as a new wall. If the section being rebuilt is over about a metre high, carries a surcharge such as a driveway or structure, or sits close to a boundary, it generally needs engineering design and certification to AS4678 and often council approval or a CDC through a certifier. We build to the certified engineered design and can arrange or advise on the engineer and certifier; the engineer designs the wall and the council or certifier approves it. A straightforward drainage retrofit on a sound low wall usually does not trigger that, but we will flag the likely position at your free assessment.

It comes down to water and slope. The region gets high rainfall and the escarpment sheds heavy runoff onto the blocks below, so there is a lot of water moving through the ground, and walls that were not drained properly simply cannot cope with it. Reactive clay soils in parts of the region swell and shrink as they wet and dry, adding movement, and many blocks are steep enough to need taller walls carrying real loads. Put missing drainage together with all that water and load and you get the leaning, bulging and cracking we are called out to fix, which is why our repairs always start with getting the drainage right.