Seismic risk on older stacks

The earthquake chimney risk in Washington

Unreinforced masonry chimneys are among the most fragile parts of an older house. In a Cascadia subduction-zone event, a tall brick stack without internal steel bracing sheds bricks and can come through the roof.

What an inspection checks

The inspection looks at whether the stack has internal reinforcing, the condition of the mortar joints, and whether the crown and upper courses are already loose. An older stack with degraded mortar is the highest-risk version.

The mitigation path

The usual path is masonry repair on the upper courses with reinforcing added, or a full rebuild of a stack past repair. The decision sits on what the inspection actually shows.