We have all read the headlines of tragic deck collapses over the years. The causes of these tragedies are typically either from inferior design, construction or even more worrying, from failures due to age and wear that went unnoticed.
According to North American Deck and Railing Association, from January 2000 to December 2006, there were 179 reported deck collapses. Of those, 1,122 people received injuries and 33 people died. According to the same source, reported deck collapses have increased at a rate of 21 percent per year over the same period. Most collapses occurred in the months between June and August when the decks are obviously in peak use and loading, while the other collapses that were reported over the winter months were typically due to excessive snow and ice loads. The failures occur when the structure can no longer resist the loading that is placed upon it.
Currently, the construction of a new deck or the replacement of an existing deck is required by law to have proper permits and municipal inspectors to issue certificates of occupancy after the deck construction is complete. This requirement is based, at least in part, due to past deck failures resulting in injury or death. The current International Residential Code (IRC) is one of the primary references for both deck designers and code officials. Among other requirements, the code contains standards on how to properly design and construct safe structures. Unfortunately, however, there aren’t any requirements for inspections of existing decks. The International Code Council does, however, recommend that exterior wood structures be inspected twice per year.
As deck structures age, the materials are subject to increased degradation and the potential for failure increases. This becomes even more critical when the original design or construction of the deck was inadequate or even marginal or the deck was not properly maintained. Periodic and detailed inspections are essential to ensure that the decks are stable and safe.
Improper Fastening Leads to Failures
Experts agree that the main source of collapse is failure of the connection between the house rim joist and deck ledger as well as post or railing failures. It is estimated that 80 percent of the deck collapses occur at the ledger to rim joist connection, the location where the deck attaches to the building.