Would your chimney withstand a quake?

Author: Ben O'Connell
Would your chimney withstand a quake?

Check that your chimney can withstand an earthquake or, if it falls, won’t cause serious damage. That’s the advice of the Natural Hazards Commission Toka Tū Ake (NHC), which is reminding people that unreinforced masonry chimneys can be a significant risk to people’s safety and the strength of our nation’s homes.

“Pretty much every major earthquake over the past 170 years has shown that crumbling chimneys pose a significant risk to people’s safety and to our homes”, says NHC Public Education Manager, Hamish Armstrong. “Brick and concrete masonry chimneys are particularly vulnerable as they can crack, shift or collapse, causing damage to people and property.”

Armstrong says that homeowners should pay particular attention if their home were built before 1970. If a chimney is found to be vulnerable, the safest approach is complete removal, which involves taking the structure down from the top to floor level, thereby fully eliminating the risk of collapse.

A more common choice is removing only the section above the roofline, as this is typically the most hazardous part. If the chimney is still in use, this portion can be replaced with a lighter metal flue.

For those unable to remove the chimney immediately, strengthening measures such as securing restraints at key points and adding plywood bracing in the roof space can reduce the risk of falling masonry reaching living areas.

Earthquakes are a fact of life in New Zealand, and while homeowners cannot control when or where the next one will strike, they can take steps to reduce damage and danger. Chimneys, because of their height, weight, and rigid structure, are often one of the first parts of a house to fail.

Even small tremors can loosen mortar and create hidden weaknesses that only become apparent during a stronger shake.

What matters is understanding the natural hazard risks and taking action where we can, Armstrong says. “We recommend engaging a licensed building practitioner to assess your chimney conditions and provide removal quotes if needed.”