Summary

A three-storey building at the intersection of Hornby and Helmcken Streets in Vancouver was being demolished. The demolition proceeded until the northwest corner with two exterior walls remained. The excavator operator pulled the floor joists to weaken the interconnection between the walls. This dislodged a horizontal beam hidden in cinder blocks in one of the walls. A portion of the cinder block wall facing north then fell outward onto Helmcken Street. After cleaning up, the demolition crew began to demolish the free-standing wall on the west side. After the excavator reached up and pulled down the top layer of cinder blocks inward into the site, the rest of the wall fell outward onto Hornby Street.

Conclusions

• During demolition, dislodgement of a hidden horizontal beam caused an unsupported, free-standing cinder block wall to fall outward onto the street. A second wall also collapsed onto the street. There was no temporary bracing to control the fall of the walls so they would fall inward onto the demolition site.

• The structural components of the older building were not adequately assessed. There was no comprehensive demolition plan with specific procedures to address the hazards.
• The demolition contractor began to demolish the building without any advice from a professional engineer regarding the structural capacity of the cinder blocks, the absence of beams and structural supports during the demolition process, and the need for shoring and bracing to provide additional support.
• The prime contractor's safety system was not adequate to address the identified deficiencies and violations that resulted in this incident. Workers were at risk and the prime contractor failed to ensure safety was coordinated on this site.