The life expectancy of the average deck in the U.S. is as varied as climate and geography. But one thing’s for sure: A deck that was improperly designed and constructed could fall apart in less than 10 years, says Don Bender, director of the wood materials and engineering laboratory at Washington State University in Pullman, Wash.
Worst case scenario: People could get hurt, even killed. Even decks that are raised just a few inches off the ground pose a danger and/or at least a big mess, should they collapse.
We spoke to Bender and Steve Pryor, building systems research and development manager with Simpson Strong-Tie (manufacturer of structural connectors for homes and decks) in Pleasanton, Calif. We pulled some information from the North American Deck & Railing Association as well to come up with a do-it-yourself deck checkup, which should be performed now, before outdoor season is in full gear. If your deck shows signs of any of these problems, call a qualified building professional, which would include a structural engineer, architect or certified contractor.
— Karen Klages, kklages@tribune.com
1. Missing connectors: A deck should be built using a series of wood, nails, screws and metal connectors — not merely nailed to the side of your house.
“If it’s an elevated deck, it’s easy to get under and see,” says Pryor. In particular, check the ledger board — the piece of framing lumber that attaches the deck to the house. It’s a critical connection. “If you don’t see hexagonal heads of a bolt or a lag screw and all you see are nail heads,” the deck is not safe, says Bender. Nails alone don’t do a good job of holding the deck to the house.
In cases where the deck is only a few feet or less off the ground, the only practical way to inspect the ledger connection is to remove deck boards to gain access from the top, says Bender. Those boards will be attached with either screws (the easier scenario) or nails.
2. Loose connections. Check for ledger boards that look to be pulling away from the house. Check for loose stairs and wobbly railings. Push on railings and banisters to ensure there is no give. Check stairs too.
3. Corrosion. Look for rust on metal connectors, nails and screws. Rust can weaken the deck’s structure. Also check connections in the ledger board, railing, etc.
4. Rot. Check for rotting wood, which can compromise stability. Pay close attention to places “where moisture can be trapped — where two members butt up against each other,” such as the deck ledger attached to the house, Bender says.
Decay is also common “where you’ve drilled holes into the lumber for a bolted connection,” Bender says. If your deck is made of a pressure-treated lumber, it’s likely the chemical impregnation didn’t extend to where the lumber was drilled out. Decay can happen here.
One of the easiest ways to find decay is to “start poking at the wood” with a screwdriver or pocketknife, Pryor says. “If it’s really soft and ‘punkie,’ it is rotted.”
5. Cracks. As wood ages, cracks may develop from the shrinking and swelling of the wood. Large cracks or excessive cracking can weaken a deck, making it susceptible to collapse. Look for significant cracking around the connections and cracks that go all the way through the piece of wood. And beware of notched posts in your railing. Some builders like to notch the post where it’s attached to the deck, Bender says. But notching can cause cracking and weaken the wood.
