Reprinted with permission from Professional Deck Builders Magazine.
The headlines scream “preventable.” These headlines often begin, “Deck [Porch, Balcony] Collapses”, and end with words like, “Killed…Injured…Hurt…Dead.” And, due to increased load, these events often occur when maximum numbers of people are exposed to harm: wedding receptions, parties, family barbecues, even wakes. These tragic stories all demonstrate the importance of building inspections of new and existing decks and why this step can literally save lives.
Take, for example, a deck collapse that injured six people in Elyria, Ohio, in June 2004. The building inspector’s report, filed just hours before the collapse, read, “The balcony’s beams were badly rotted and work done earlier in the day to shore up the rotted beams did nothing to resolve the structural problem.” It’s estimated that 2.5 million new or replacement decks were built last year. Almost every new home being built today includes an elevated deck or porch. And, existing decks on older homes are being replaced at a very high rate. In fact, the number of personal injuries and deaths related to decks each year is likely to continue to rise because more decks are being constructed each year and existing decks are deteriorating.
The International Code Council (ICC) suggests looking for the following when inspecting decks, balconies, or porches: split or rotting wood; loose or missing nails, screws, or anchors where the structure is attached to the building; missing, damaged, or loose support beams and planking; and, wobbly handrails or guardrails.
CONNECTIONS ARE CRITICAL ELEMENT
The International Residential Code (IRC) requires residential decks and porches to withstand a minimum of 40 pounds per square foot plus the weight of the porch. Balconies, which are only supported where they connect to the building without additional posts, should withstand 60 pounds per square foot. Experts agree that the main sources of injuries are failures of the connection between the deck ledger and house band joist and railing related accidents. “We are particularly concerned with the method used to attach the deck to the house,” said Roger Robertson, Chief of Inspections for Chesterfield County, Virginia, where about 4,000 decks were inspected last year. Mark Schwarzwalter, Senior Building Inspector, City of Sammamish, Washington, often sees ledger problems during his inspections. “The ledger attachment has not been done according to the plans, the handrail heights are not per code, or the builder hasn’t requested the required inspections,” he said, citing the most frequent issues seen in the 175 decks that are inspected annually in Sammamish. Nail connections can be a problem because, unlike bolts, nails can pull out.
The U. S. Forest Products Laboratory in Madison, Wisconsin, studied five years of newspaper articles on deck collapses from around the country while researching a deck-building manual. The research showed that “nearly every collapsed deck had been attached with nails, rather than bolts, and investigators had pinpointed nails as the cause of the collapse.” Dozens were injured when the 12-year-old deck of an Atlanta mansion collapsed during a Salvation Army party in 1995.
One couple attending the party sued, claiming the host allowed too many people to gather on the wooden deck and that he should have warned them that the deck was unsafe. After the collapse, a building inspector found that the collapsed section had been attached with 12d nails – 3 1/4 inches long.
The tips of the nails had penetrated the 3/4 – inch siding but not the cellulose beyond it. Unknown to the homeowner, the builder had not used flashing and the wood behind the beam was rotten. A screwed-in connection works differently than a nail by gaining increased strength from the wedging action of wood fibers along the entire length of the shaft. For every inch of penetration, lag bolts have as much as nine times the pullout resistance of a nail. A thru bolt gives even better resistance with its metal-to-metal connection. The thru bolt is inserted in a drilled hole and fitted with a nut on the other side. A washer on both sides spreads the pulling force over a larger portion of the beam. The screwed-in connections offer another benefit over nails. They resist the expansion and contraction of the wood. They may, however, loosen over time. Early signs of such loosening include a widening gap between the house and the deck. With nails, the deck may fall without any warning signs. Yet, bolts aren’t without their own challenges. In fact, lag bolts had been used on an elevated porch on a Chicago apartment building.
When that porch collapsed on June 29, 2003, 13 people were killed and more than 40 were injured. Inspections showed the lag bolts were actually bent. “If you don’t get it exactly right, they (lag bolts) are worthless,” said David J. Kupets, a partner with Kupets & DeCaro, the Chicago law firm representing several victims of the collapse. “There’s a lot of detail about attachments, but building codes and construction documents still don’t give an appropriate use of ledger board with masonry structures.” He likens the lag bolt failure to an improperly installed expansion hanger for a large piece of art. The hole in the wall gets bigger and the hanger cannot expand enough to establish a rigid position.