The most recent phase of construction on the St Mary's campus began in 2017 with the purchase of the property on the West hand side of the school. After demolishing the existing buildings on the property, the St Mary's school building was extended onto the new property with four temporary demountable classrooms installed on the Presbytery grounds to cater for classrooms displaced during construction. After the completion of the construction in February 2018, the demountable classrooms remained to accommodate the students of Marist Catholic College North Shore whilst their campus was renovated in 2020.