
- Overload… Too many people on a balcony or deck is a common reason for the collapse of such structures or when the occupancy of areas are changed without an evaluation
- Lack of maintenance… A lack of maintenance will lead to things like not noticing a problem before it becomes catastrophic
- Use of inferior materials/chemicals… Such as older (1960s – 1980s) fire retardant treated wood roof assemblies made with cheap ammonium phosphate are prone to collapse after 25 years of service
- Bad engineering… Structural engineers make mistakes, everyone does, but in small firms, a lack of multiple people checking designs can lead to bad calculations and structural failures
- Under-designed… Don’t confuse this with bad engineering, under-designed means you followed the code correctly and performed good calculations, but it still was inadequate for the loads
- Fire… Fire reduces steel yield strengths, causes concrete to undergo chemical changes that weaken it, causes masonry to spall/crack, and will consume wood materials… All of which can result in collapse
- Bad construction… The most common reason for an attached and self-supported deck to collapse is the contractor only provided nails between the deck ledger and the structure of the house, resulting in the deck pulling away
- Impact damage… Such as someone driving a car into a house, which can result in partial collapses
- Storm damage… Winds generally don’t result in a collapse as things are lifted away and not falling downwards, but floods can cause buildings/bridges to collapse
- Soils… Development of a sinkhole (human-made or natural) can cause a building/bridge to collapse
- Seismic… Earthquakes can make just about anything collapse if it is not designed for the magnitude of accelerations occurring.