Wall Demolition and Construction Wenona School
- Client: EH Stonemasonry
- Principal: Northern Group
- Date: August 2015
Northern Contracting Group were engaged by EH Stonemasonry to undertake demolition works of an existing unstable heritage sandstone retaining wall and the construction of a reinforced block retaining wall at Wenona School in North Sydney
The demolition of existing stone retaining wall was undertaken carefully as the stone was to be reinstated in the order in which it was removed. The method used by NCG was with the use of a 4.5t excavator with a set of cushioned grabs (Probst type). Each stone had to have the mortar loosened by hand and the back for the wall soil unloaded to take the pressure of the remaining wall. This was to ensure the unstable section of the wall did not collapse. On completion of the wall demolition the existing site soil had to be removed at the angle of repose to ensure there were no soil collapses during the extensive reconstruction works.
A reinforced coreflled block retaining wall was constructed over a stepped footing to retain the aggregate backfill behind. The sandstone wall to be reconstructed as a cladding in front of this block wall.
Subsoil drainage was installed including a penetration through the wall to ensure water that gets behind the wall can escape without building up and causing pressure and possible retaining wall failure.
The site was very difficult to work in as it was only 3m wide with one access point for deliveries and cartage and disposal. NCG were required run 2-4t tipper trucks of filling for disposal and backfill aggregate for reinstatement. The access issues coupled with the close proximity to the school ensured works were adequately supervised with all movements were undertaken outside peak times and under traffic control when required. Flexibility which the school appreciated.