THE PROBLEM
18-20 Newton Street Alexandria is a complex of 32 units situated on a former industrial site in the inner western suburbs of Sydney. Completed in 2001, the three buildings that comprise the development developed severe structural issues determined to be due to differential settlement between areas of the complex founded on deep piles and those areas at the perimeters of the complex that were founded on a combination of strip footings and ground beams. Additionally, the complex suffered water damage throughout, due to poorly executed waterproofing. Also, numerous general building defects existed, such as defective cavity flashing, drummy and cracked render and internal defects.
THE PROCESS
Owing to the need to stabilize the building prior to reinstating finishes, the process was managed in a strict sequence that allowed settlement times before loading the new piles. After the client’s consulting engineer had given the go-ahead, the piles were loaded, and jacking took place, to transfer the building load to the new substructure.
The reinstatement of external structures and finishes was then undertaken including reinstatement of the road, footpaths, nature strip and the reinstatement of the interior of the residential units.
The owners also took the opportunity to redesign the internal courtyard of the building to include a community garden and barbecue area for the enjoyment of the residents.
THE SOLUTION
To prevent further subsidence, a foundation solution consisting of 11m deep large diameter continuous flight augered piles was installed around the complex. Load was transferred to the piles via pile-caps and tie beams and the building’s exterior facade was reinstated.
In conjunction with the foundation works, the waterproofing deficiencies were rectified, and an internal works programme was completed including works to all the occupied units.
