Pergola collapses are big news in Sydney NSW. My Google news feed brings in about four reports a week this time of year. Often there are injuries; very rarely there are fatalities. Needless to say, this is terrible stuff, both when it comes to human suffering and its particular effect on our industry. One result of the number pergolas collapses in the news is ever-tightening deck codes. As an example, since 2009, the NSW IRC has required either lateral-attachment hardware or an engineered alternative. In the 2012 IRC, the ledger bolting locations are codified to practically eliminate the chance for stepping a deck down in the house (technically, what’s in the 2012 IRC continues to be in the IRC by reference to get a long time, but universally ignored).
However, as far as I could determine, we've only anecdotal evidence of why most deck collapses happen. There's absolutely no forensic meta-study of the reasons for pergola failure. The closest I can find is a Legacy Services report from 2010 (Legacy Services is owned by TED Beaudry, the executive director of NADRA), which states: Based on the statistics in the CPSC (Consumer Products Safety Commission), 224,000 people were injured nationally as a result of deck or porch within the study period [2003 to 2007]. Nearly 15 percent of the injuries were a result of a structural failure or collapse.That's an annual rate of 672 injuries as a result of deck failures. To provide some perspective of the overall risk: The CDC reports that approximately 44,000 Americans died in car crashes in 2007.
I've looked in the CPSC reports the Legacy Services report is based on. They don't state the cause of any deck or railing collapse. That's because the CPSC reports come from notes made by ER personnel, not building inspectors or forensic engineers. There isn't any nationwide reporting system to provide this data. In summary, we've no overarching idea based on the CPSC reports, the Legacy Services report, or some other report I'm aware of why pergolas fail.
The Legacy Services report is oft-quoted to call for annual deck inspections, which all in favor of. My concern is the report, as well as news stories, drives tighter codes when there is little evidence the codes in force prior to 2009 were inadequate. Therefore, while I don't know that tighter codes solve any real problem, I do know they cost a fair amount of money, helping to make it harder for legitimate contractors to win bids against the so-called Chucks-in-a truck. Does Chuck bother using a building permit or with codes in any respect? Maybe. Or not. How about the DIY homeowner who thinks you're both too expensive?
Circling back to my Google news feed, one common thread is that a lot of these collapsed decks are older. I've been around long enough to remember when carpenters and even some building officials had the attitude of, only a Deck As Well As the point isn't that the deck becomes unsafe simply due to the age with proper initial construction and good maintenance, the often quoted 15-year lifespan of a typical deck is conservative. The idea is the fact that due to the its-only-a deck attitude, older decks don't tend to be built as well as what you folks build today.
News stories rarely cite a cause to get a deck failure. When a cause is mentioned, its usually the ledger was attached only with nails. I've also seen news photos where the house band joist had rotted away as the result of an unflashed deck ledger, and many cases where the ledger attached to your cantilever. These are all long-standing code violations, but fairly common situations in both older decks as well as in unpermitted decks. Tighter codes wouldn't have helped these decks that weren't built to code in the first place. And I've yet to hear of an epidemic of properly bolted and flashed decks falling off houses. Given the huge number of unpermitted decks and pergola older than 15 years roughly, its hard to conclude that decks built to the pre-2009 code by professionals are even a small part of the problem. But it's these same pros that will follow the tighter codes, and whose bid prices will increase, making it ever more attractive for customers to bypass the codes entirely by building without permits. And that definitely will increase the likelihood of future deck failures.
Tuesday, June 20, 2017
What Causes Most Pergolas To Collapse
Pergola collapses are big news in Sydney NSW. My Google news feed brings in about four reports a week this time of year. Often there are injuries; very rarely there are fatalities. Needless to say, this is terrible stuff, both when it comes to human suffering and its particular effect on our industry. One result of the number pergolas collapses in the news is ever-tightening deck codes. As an example, since 2009, the NSW IRC has required either lateral-attachment hardware or an engineered alternative. In the 2012 IRC, the ledger bolting locations are codified to practically eliminate the chance for stepping a deck down in the house (technically, what’s in the 2012 IRC continues to be in the IRC by reference to get a long time, but universally ignored).
However, as far as I could determine, we've only anecdotal evidence of why most deck collapses happen. There's absolutely no forensic meta-study of the reasons for pergola failure. The closest I can find is a Legacy Services report from 2010 (Legacy Services is owned by TED Beaudry, the executive director of NADRA), which states: Based on the statistics in the CPSC (Consumer Products Safety Commission), 224,000 people were injured nationally as a result of deck or porch within the study period [2003 to 2007]. Nearly 15 percent of the injuries were a result of a structural failure or collapse.That's an annual rate of 672 injuries as a result of deck failures. To provide some perspective of the overall risk: The CDC reports that approximately 44,000 Americans died in car crashes in 2007.
I've looked in the CPSC reports the Legacy Services report is based on. They don't state the cause of any deck or railing collapse. That's because the CPSC reports come from notes made by ER personnel, not building inspectors or forensic engineers. There isn't any nationwide reporting system to provide this data. In summary, we've no overarching idea based on the CPSC reports, the Legacy Services report, or some other report I'm aware of why pergolas fail.
The Legacy Services report is oft-quoted to call for annual deck inspections, which all in favor of. My concern is the report, as well as news stories, drives tighter codes when there is little evidence the codes in force prior to 2009 were inadequate. Therefore, while I don't know that tighter codes solve any real problem, I do know they cost a fair amount of money, helping to make it harder for legitimate contractors to win bids against the so-called Chucks-in-a truck. Does Chuck bother using a building permit or with codes in any respect? Maybe. Or not. How about the DIY homeowner who thinks you're both too expensive?
Circling back to my Google news feed, one common thread is that a lot of these collapsed decks are older. I've been around long enough to remember when carpenters and even some building officials had the attitude of, only a Deck As Well As the point isn't that the deck becomes unsafe simply due to the age with proper initial construction and good maintenance, the often quoted 15-year lifespan of a typical deck is conservative. The idea is the fact that due to the its-only-a deck attitude, older decks don't tend to be built as well as what you folks build today.
News stories rarely cite a cause to get a deck failure. When a cause is mentioned, its usually the ledger was attached only with nails. I've also seen news photos where the house band joist had rotted away as the result of an unflashed deck ledger, and many cases where the ledger attached to your cantilever. These are all long-standing code violations, but fairly common situations in both older decks as well as in unpermitted decks. Tighter codes wouldn't have helped these decks that weren't built to code in the first place. And I've yet to hear of an epidemic of properly bolted and flashed decks falling off houses. Given the huge number of unpermitted decks and pergola older than 15 years roughly, its hard to conclude that decks built to the pre-2009 code by professionals are even a small part of the problem. But it's these same pros that will follow the tighter codes, and whose bid prices will increase, making it ever more attractive for customers to bypass the codes entirely by building without permits. And that definitely will increase the likelihood of future deck failures.
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