A Safe Deck Starts With The Builder
Thu, 4 Mar 2010
A MATTER OF LIFE AND DEATH
by Anne W. West
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.
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.
RAILINGS ALSO REQUIRE ATTENTION
Because railings are the most visible element of a deck, they offer the builder an opportunity for creativity. They can be made of many materials, formed to different shapes and connected in many ways. However, builders must remember that the railing design must adhere to local building codes that are designed to ensure safety. Typically, if a deck is more than a certain distance from the ground, as little as 18 inches in some areas, railings are required for safety purposes. Codes specify a certain maximum opening between balusters, spindles, or pickets so that a 4-inch diameter ball won’t pass through the railing.
The height of the railing is also regulated, with a height of 36 inches standard for residential properties and 42 or 48 inches most common for commercial and fencing applications. Builders must understand loading and how to properly attach railings. "We're particularly leery of installing the vertical guard rail members so that they aren't attached to the deck framing and the top and bottom rails and the verticals are not attached to the deck surface," Robertson noted, pointing out that this method doesn't typically withstand the IRC's 200 pound code requirement for rails to resist a load. "We’re also seeing some deck builders who are notching the deck posts that extend from the footing and form part of the guard rail to accommodate another member. They don't realize that they are in effect creating the weakest point in that post because of the notch. We advise builders that we will not accept any type of support post with a notch in it."
Charlottesville Building Inspector, Darin Clements knows first-hand the problems caused by weak support posts. In December 2003, he was called to an emergency where an older deck guardrail had failed and a woman had fallen 14 feet to her death. "The attachments failed where the guardrail support posts were attached to the deck and where the guardrail was attached to support posts," he said. After the tragedy, Clements suggested that the inspection staff carry photos of that deck failure to help explain the importance of proper railing attachments.
INSPECTIONS NOW AVOID PROBLEMS LATER
"Experienced builders know how much wood moves and what the weather does to wood, even treated wood," Elliott pointed out. "Wooden structures built without the benefit of a roof will not last forever, even though the wood is treated to resist the effects of the weather." But, older wood is not always the problem. The Chicago deck was just five years old. "The inspection is important even before the deck is being built because the structural engineer needs to determine what type of materials are necessary to build that specific porch," said Kupets. Kupets contends that the Chicago deck was in violation of both the Chicago building code and customary practices in the construction industry. He cites a ledger board that was attached with improper screws and lag bolts and wasn't attached in enough places, the wrong size lumber, the wrong fasteners, and the wrong construction method for a porch of this size as key factors related to the collapse. As a result of this deck failure, the city of Chicago has issued a series of porch construction documents that are available online at www.cityofchicago.org.
Charlottesville Building Inspector and Plan Reviewer, Denise Burgess agrees with the need to fully understand the scope of the building project as well as the intended use of the deck. She works with homeowners and builders to better understand how the deck is going to be built even after she has seen their drawings. "We are now seeing more guardrails and supporting posts installed to code and per our instructions," she added. The ICC recommends that homeowners, condominium owners, and apartment dwellers visually inspect porches, balconies, elevated freestanding decks, and similar structures at least twice a year.
"From a structural design and building code standpoint, an elevated deck is the most challenging element of a house, because the vertical and lateral load support system and railing system are not addressed by prescriptive details in the model building codes. "Load requirements are given in the IRC, but construction details needed to satisfy the design loads are not presently in the code," said Frank Woeste, P.E., Professor Emeritus at Virginia Tech. Woeste's summation shows how critical construction plans, permits, and inspections can be to a deck's structural integrity. Both new and replacement decks require a building permit before construction begins. Although specifics vary by locality, required inspections are typically for footings (before pouring concrete), framing and final completion. Other code inspections, such as an electrical inspection, may be required based on the deck design. Robertson's team works to make inspections convenient for builders. "Permit holders can call us for both inspections (footings and framing/final) at the same time if they leave the footings open so we can see what was used for footing and we can check footing and framing at the same time," said Robertson. "We can combine framing and final inspections because everything is visible at that time, unlike a house where walls would cover up framing." So complicated is the inspection of residential decks, balconies, and porches that researchers at Virginia Tech produced the Manual for the Inspection of Residential Wood Decks and Balconies in 2003. The manual was published by the Forest Products Society in cooperation with the ICC. Researchers for the project investigated eight decks and balconies in Virginia and found that not one met all code provisions based on the 2000 IRC, which was adopted by the State of Virginia in 2003 as the model code for residential construction. The latest versions (2000 or 2003) of the IRC, deemed the industry standard, have been adopted by many localities.
Many communities make amendments to the model IRC to accommodate specific issues in their geographic area. For example, Virginia amended the section dealing with stair geometry. Code development and amendments occur at the local and state level. Deck builders have several opportunities to participate through public hearings and other public input vehicles.
Robertson encourages builders to participate in the process. "With respect to the permitting and inspection process, the building inspector is not the builder's adversary. He is your partner because we are both trying to achieve the same thing," he said. Many communities are putting codes and details of the permitting and inspection processes online to make it easier for the builder. For example, the City of Sammamish posts local amendments to the IRC on its Web site at www. ci.sammamish.wa.us. "Information can also be found at a Web site shared by nine cities in our area," said Jan Vogee, building official, City of Sammamish. "The Eastside Building Officials Partnership provides tip sheets, inspection checklists, and some online permits at www.mybuildingpermit.com."
KEEPING UP WITH CHANGES
Building inspectors, like deck builders and homeowners, are challenged to keep up with the deck industry. There are changes to the IRC every three years. State and local amendments are added to those changes. New building materials and deck-related products are appearing on the market in record fashion. Reading industry magazines, consulting with other inspectors on a regular basis, and monitoring state building and code official association Web sites and message boards are all good ways to stay abreast of new products and inspection challenges. And, in some cases, the builder is required to educate the inspector. "We see new deck materials and construction methods during on-site inspections and look at manufacturer specifications," said Ronn Seaward, building inspector, City of Sammamish. "We read the industry publications and when we see a new product in the field, we require the builder to provide product information," said Roberston. "For instance, if it’s a composite material we need to make sure it is going to span the distances, or if it’s a deck ledger bracket we need to be sure it will support the load it is supposed to. With the new composite materials, we need to make sure that whoever is putting it up is attaching and supporting it the way it’s supposed to be because you can’t support plastic the same way you would wood."
The results of good construction, building inspection, and plan review are often unseen, according to Elliott. "The absence of TV news reports of building code-related accidents and no calls from attorneys concerning those accidents are peripheral goals of every inspector," he said. Robertson summed up why deck inspections are so critical. "No one wants to build an unsafe deck and that's what it's all about." And as deck collapses continue to make headlines, the focus on safety and the quality of deck construction is bound to be strengthened.
Re-printed courtesy of Professional Deck Builder Magazine. Published bi-monthly, Professional Deck Builder Magazine strives to educate and inform professional deck, dock, and railing builders; to provide a venue for manufacturers and suppliers to reach their buyers; and to contribute to the growth and professionalism of the industry. For your free* subscription call 678-344-6283.
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