By Bud Coburn
Wind and other elements may cause an already weakened chimney to collapse. An elderly man in Britain was crushed by a wind-toppled chimney as it fell from the roof of the managed-care facility where he lived. This case is, unfortunately, fairly unremarkable, as such accidents occur often for a variety of reasons — from weathering and wind, to falling tree limbs and poor design.
- mortar between the bricks or stones that crumbles when poked with a screwdriver;
- missing or insufficient lateral support — typically, steel straps — used to tie the chimney to the structure at the roof and floor levels. Building codes in some seismically active regions require internal and external bracing of chimneys to the structure;
- mechanical damage to the chimney, such as that caused by falling tree limbs or scaffolding;
- visible tilting or separation from the building. Any gap should be frequently measured to monitor whether it is increasing; and
- chimney footing defects, including the following:
- undersized footing, which is footing cast so thin that it breaks, or does not sufficiently extend past the chimney’s base to support its weight;
- deteriorated footing, caused by weathering, frost, loose or poor-quality construction; and
- poor soil below footing, including eroded, settled or otherwise weakened soil, frost heaves or expansive clay beneath the footing.
- Attach plywood panels to the roof or above the ceiling joists to act as a barrier between falling masonry and the roof.
- Strengthen the existing chimney by repairing weak areas.
- Tear down the chimney and replace it with a flue or a stronger chimney. Keep in mind that tall, slender, masonry chimneys are most vulnerable to earthquakes, weathering, and other forms of wear. However, even newer, reinforced or metal flue chimneys can sustain significant damage and require repair.
- Relocate children’s play areas, patios and parking areas away from a damaged chimney.
- Instruct family members to get away from chimneys during earthquakes.
Homeowners should contact their local building departments to obtain required permits before starting any significant construction that may affect the chimney structure and/or its supports.
In addition to collapse hazards, leaning chimneys can also make using the fireplace dangerous. Hearth cracks, side cracks in the fireplace, openings around the fireplace, and chimney damage all present the risk that sparks or smoke will enter the living space or building cavities. Check for evidence of fireplace movement. Following an earthquake, homeowners should have their chimney inspected before using the fireplace.
Commercial chimney collapses are rare, but they deserve mention due to the devastation they cause. In one terrible incident in central India, more than 100 workers were killed when a 900-foot (275-meter) tall chimney collapsed on a construction site. One of the worst construction site disasters in recent history, the collapse was blamed on heavy rain. While safety standards are generally more stringent outside of India, commercial chimneys everywhere require inspection.