Sudden collapses of residential decks aren't just a U.S. phenomenon. That's one lesson to be drawn from a failure on Sunday morning, September 22, in Dartmouth, Nova Scotia. CBC News has the story ("Dartmouth wooden deck collapse sends 15 to hospital").
CBC reports: "Halifax Regional Police Staff Sgt. Bill Morris said about 15 people were on the 3.5-metre high deck when it fell to the ground. Two people were underneath the deck. All of them were taken to hospital. Four of those people have serious, but non-life threatening injuries."
Photos from the scene show an intact deck lying in one piece on the ground. Evidently the collapse was another case of the classic failure pattern: The connection holding the deck ledger to the house failed suddenly under the load of people standing on the structure.
The September 2013 issue of JLC has a look at best practices for deck construction ("Best Practices: Decks," by Michael Chotiner and JLC Staff) (subscription required). "Based on what we have seen, two types of connections in particular are most vulnerable: the connection of the ledger to the house, where fasteners are undersized, inadequately linked to house framing, and poorly flashed against water intrusion; and at the guardrails, which are almost never anchored to withstand the forces they could be called upon to resist," the story reports.
Below is one effective solution for attaching the ledger board to the house floor system band joist to make the "positive attachment" required by recent versions of the International Residential Code.
Where a strong attachment to the building isn't practical—as in the case of some masonry-veneer exteriors—a freestanding deck may be the better alternative (see "Building a Freestanding Deck," by Jim Finlay, JLC 12/2011).
