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.
FLASHING CAN FAIL
Flashing is another important consideration in deck building. "We suggest that builders consider building freestanding decks because this eliminates the potential for water to get into the flashing if it is not installed correctly," Robertson pointed out. When water does leak under the flashing, the wood begins to rot and the deck's foundation is weakened. The homeowner isn't aware of the problem until it's too late and both the deck and the house are impacted by rotten wood.
Many inspectors strongly discourage placing a deck directly under the sill of an exterior door. "We suggest about a four-inch distance between the threshold and the top of the deck to keep water from getting under the threshold and eventually rotting out the sub flooring," Robertson said. Because holes made in the side of the house, even when filled with a bolt, may allow water to seep in, builders should fill holes drilled for bolts with a durable caulk such as silicone. It's also important to pay close attention to products that are used in flashing. "We look for rubber or copper in flashing, and we are working to educate the public on the danger of mixing aluminum flashing with the new treated wood products," said Tom Elliott, building official, City of Charlottesville, Virginia. He says his team, which inspects about 450 decks a year, spends as much as 60 percent of their time educating others on the details of building codes.
Recent changes in the chemicals used in the manufacture of treated wood have had an impact on materials used in flashing. According to the lumber and fastener industry, the newer chemicals being used to treat wood, alkaline copper quaternary (ACQ) and copper azole, are considerably more corrosive than wood previously treated with chromated copper arsenate (CCA). This means special attention must be paid to fasteners, hangers, and other materials that may come in contact with the wood because aluminum flashing actually deteriorates and dissolves when it comes in contact with treated wood.
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