South East Queensland Body Corps Face Big Dry Problems
Long dry spells do more than turn the lawn brown in South East Queensland. Much of the region is built on reactive clay soil, which expands when wet and shrinks when it dries out. With a super El Niño forecast to bring an extended dry period, that soil movement is set to become a real concern for property owners, especially for body corporates responsible for older buildings. As the clay loses moisture and retracts, that movement can affect a building’s foundations, and depending on the age and design of the building, the consequences can be both cosmetic and structural.
Whilst in a house this might cause hairline cracks, the same movement in a high rise or multistorey building can cause cracking through slabs, footing and facades, and in older buildings that can compromise the structure itself. Regulations requiring specific engineering assessment for reactive soil, under AS 2870, only came into effect in 1986. Whilst this applies to houses, not high-rise buildings, it’s generally seen as the point where reactive soil began to be treated more seriously in construction. This means buildings that went up before the mid 80s weren’t designed with the knowledge in mind that we now have about how reactive soil behaves, which puts them at higher risk during extended periods of dry weather.
Where are the Hotspots?
Gold Coast
Parts of Pimpama, Upper Coomera, Ormeau and surrounding suburbs can see ground movement of up to 75mm during dry periods. Further inland, parts of Nerang, Mudgeeraba, Worongary, Tallai and Bonogin are classified as high risk, with movement in excess of 75mm.
Brisbane, Logan and Ipswich
Parts of Logan, Springwood, Ipswich, Kenmore Chapel Hill are all classified as high-risk zones.
Sunshine Coast
Parts of Nambour, Yandina and Tewantin also fall into the high-risk category.
While reactive clay soil is a risk for any building constructed before 1986, it’s likely to have more dire consequences for multistorey and high-rise buildings. Movement that might require minor repairs in a double-storey home, could affect load-bearing elements across dozens of units in a multistorey building.
Body corporate and strata managers in these areas are being encouraged to schedule regular monitoring of both the building slab and the façade, so any early movement is picked up before it becomes a bigger, more expensive problem. For buildings that fall into the older, higher-risk categories, that means getting an inspection done now rather than waiting for visible cracking to appear.
Getting a professional assessment is the first step, whether that booking high rise inspections to check for early signs of movement, or organising high rise concrete repairs where damage has already set in.
