More than 2 million decks are built and replaced each year in North America.  InterNACHI estimates that of the 45 million existing decks, only 40% are completely safe.
Because decks appear to be simple to build, many people do not realize that decks are, in fact, structures that need to be designed to adequately resist certain stresses. Like any other house or building, a deck must be designed to support the weight of people, snow loads, and objects.  A deck must be able to resist lateral and uplift loads that can act on the deck as a result of wind or seismic activity.  Deck stairs must be safe and handrails graspable.  And, finally, deck rails should be safe for children by having proper infill spacing.  

A deck failure is any failure of a deck that could lead to injury, including rail failure, or total deck collapse.  There is no international system that tracks deck failures, and each is treated as an isolated event, rather than a systemic problem.  Very few municipalities perform investigations into the cause of the failure, and the media are generally more concerned with injuries rather than on the causes of collapses.  Rail failure occurs much more frequently than total deck collapses; however, because rail failures are less dramatic than total collapses and normally don’t result in death, injuries from rail failures are rarely reported.