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The North American Deck and Railing Association estimates that 2.5 million decks are built each year. At the time of construction, deck builders can prevent four of the most common causes for deck collapses by taking care during installation to:

1. Use lumber treated with preservatives that will prevent the deck boards from rotting.
2. Screw, don't nail, the deck to the building using zinc-coated, corrosion-resistant fasteners, joint hangers and anchors made from galvanized steel, stainless steel, silicon bronze or copper. Local building codes detail the size and number of fasteners required.
3. Laterally brace the deck to anchor it against strong winds. Install footings that will support the deck from downward loads and prevent it from lifting during a wind-driven storm.
4. Install guardrails on any deck, porch or balcony that is more than 30 inches off the ground. Most codes require the railings to be at least 36 inches high with slats every four inches. Similar rules apply to railings on staircases.

Extra steps for prevention

Even a well-constructed deck is at risk of collapsing if it's overloaded, poorly maintained or has outlived its expected lifespan. And even deck builders who followed every rule and took every precaution could find themselves on the wrong end of a liability lawsuit if a by-the-book balcony falls and injures someone.

Although building codes do not require it, it's not a bad idea for contractors to take an extra step toward preventing a deck collapse: Educating the building's owners about the importance of weight limits and maintenance to keep the structure safe. Here are five tips to pass along:

1. Leave a sign behind that posts the maximum capacity for the balcony or deck so that the building owner will know. Also, advise the owner that a pileup of snow on a deck can be heavier than a group of people, and can lead an otherwise empty deck to collapse.
2. Advise owners that decks do not last forever; in fact, deck professionals give even the best-made structures a lifespan of 15 years. Rusted nails or fasteners can be compromised. Splinters, loose or warped boards and popped nails are signs of deterioration. Professional deck builders know local codes for deck-building, and follow them strictly, as that is the first thing an inspector will check for after a deck has collapsed. One easy fix that could save lives: Older decks often have railings that are too low for safety because outdated codes allowed them to be built at shorter heights.
3. Leave instructions for the building owner about how to maintain the deck. Railings and supports should be regularly examined for broken or missing pieces; decks need regular cleaning, as dirt, water, dead animals and falling leaves can decay the wood.
4. Any movement or swaying on the deck can indicate that the structure needs cross-bracing. Alert the owner to call for repairs and stay off of the deck if it starts to move.
5. Encourage building owners to have their decks inspected periodically so dry rot and other issues that could compromise the structure can be repaired before they lead to tragedy. The North American Deck and Railing Association estimates that at least 40 million residential decks and 10 million commercial decks in the U.S. are at least 20 years old.