Repair not rebuild: The Buchan Group reuse existing fabric for Christchurch earthquake project

The reconstruction of an earthquake-shaken apartment complex in New Zealand’s Christchurch has demonstrated the economic viability of reusing an existing building structure when possible, says project architects The Buchan Group.

Riverside Apartments on Christchurch’s Carlton Mill Road were damaged during the 2012 earthquakes and have since been given a facelift and structural remediation by The Buchan Group who decided it was best to repair rather than knock-down and rebuild the existing building.

The five apartments within Riverside cover a total of 1,400sqm and besides an internal facelift received mainly external and structural upgrades from The Buchan Group.

The entire exterior façade of Riverside was replaced by a series of composite aluminium and solid plaster panels which the architects say provides a low maintenance and Christchurch-themed finish.

“This redesign now showcases strong external design features resulting in a visually impressive and simplistic building which we feel embraces the new, forward-thinking vision for Christchurch City,” said The Buchan Group’s Christchurch-based Practice Manager Raylene McEwan.

A requirement for the redesign was to meet the tightened New Zealand earthquake resistant standards which meant the entire building was re-levelled and its structural foundations reinforced.

This was completed following the removal of the old façade and using a jet grouting technique under the foundations.

Jet grouting is a grouting technique that creates in situ sections of soilcrete (grouted soil), using a grouting monitor attached to the end of a drill stem. The monitor is sent into the earth to the appropriate depth before high velocity grout jets (on the side of the monitor) erode and mix the soil.

Jet Grouting cross section courtesy Ascon Road Construction.

Hardening agents are added to create soilcrete geometries which are used to underpin existing foundations, construct excavation support walls, and construct slabs to seal the bottom of planned excavations.

The Buchan Group used the technique to correct the building’s level and structural foundations and McEwan said her team’s choice to repair rather than rebuild highlighted an important lesson for architects.

“This project shows it is physically possible and economically viable to repair earthquake damaged buildings, to bring them up to current building code requirements and return them to function rather than having to demolish and construct new in every case,” she said.

The reconstruction took nine months. The Buchan Group wouldn't comment on the cost of the project nor the projected savings as a result of the project.