Demolition work will begin in Christchurch this morning to clear the remaining parts of the Sumner - Redcliffs RSA building.

Severely damaged by rock-fall in the 2011 February earthquake, the Wakefield Avenue site was red-zoned as an ongoing public risk.

One person was killed by rock-fall near the building.

CERA's project manager for Port Hills Clearance Brenden Winder says the demolition is risky.

"So we'll be taking all the proper precautions in monitoring the cliff. This site is fenced off and we shouldn't have anyone too close, so we're not anticipating any adverse reaction from that cliff, but just in case we've got those procedures in place."

Brenden Winder says the demolition work will take around four days to complete.