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Based on three years of research at Virginia Tech and Washington State University, the new guidelines favor lag screws and 1/2 inch bolts and advise builders how far apart to space them, depending on the span of the deck joists (see "Code Changes," above). Many local governments are going a step further, requiring or at least recommending that decks be built so they can stand on their own—even if they are attached to a house.

The deck–building industry, including professional installers, trade associations, and manufacturers of decking materials and fasteners, is stepping up with campaigns aimed at do-it-yourselfers, who often skip the inspections and skimp on quality products to save money. In addition, manufacturers have fashioned longer–lasting fasteners to better withstand contact with harsh weather and corrosive wood treatments, and have created elaborate systems that anchor the deck so it supports not just vertical weight—the things and people on the deck—but also lateral weight—the movement of that weight, which occurs when people jump, dance, or walk.

"It doesn't take much for people at a party to wander outside because it's warm, to start telling a story that requires them to start jumping up and down," says Janet Arden, managing editor of DeckWorld magazine, a publication for deck builders and manufacturers of deck materials. Frank Lesh, president of the American Society of Home Inspectors, agrees: "When you've got a deck, especially when you've got young people, you're going to have a party."

One too many parties on an improperly attached deck all but guarantees a tragedy. Around 40 percent of decks are built by handy homeowners, estimates Katwijk. And too many of them are skipping the deck inspections, says Raoul Newman, assistant director for inspections for Atlanta's Bureau of Buildings.

"The biggest problems we have are with the weekend builders who go to [The] Home Depot and get a quick how-to-build-a-deck-over-the-weekend course and they don't get a permit," he says. "Will there be deck failures? They're going to happen. But probably when that occurs, you're going to find out it wasn't permitted. I would say permitted decks are properly done."