According to my research, there have been 23 deaths and hundreds of serious injuries do to deck failures since 2000. A properly designed and built deck cannot be overloaded even if you stacked people onto it shoulder to shoulder. There are two main reasons for deck failures. 1) The ledger (the board that runs parallel to the side of the house and supports the edge of the deck, securing it to the house) is just nailed onto the house. Half the weight of the deck is on the ledger board and nails have a tendency to slide out over time. A ledger board needs to be attached to the house with fastners that are compatible with pressure treated lumber such as galvanized bolts, lags, or ACQ compatible Star Drive Lag Screws™. 2) ROT! Decks that have not been built correctly or have not been maintained are more susceptible to damage and weakening due to rot.
Look for rot’s discoloration in the lumber or anything growing out of the wood. Test for rot by stabbing the wood with a sturdy knife point. If your knife goes in more than one quarter of an inch or you find spongy spots, that means the wood is decaying. If only a few boards are damaged, replace them. You cannot get away with leaving the rotten boards and putting a new board beside it. This will only accelerate the rot by providing fresh food for it. The rot will quickly invade the new board. If you find soft spots in the support posts or beams, you will need to rebuild the deck. (This requires a building permit.) To minimize future problems, hire a professional that specializes in decks.
Assess whether the structure is solid. When you walk on the deck, you should not feel it move. It should not tilt. The railing should be firm and not moveable. The fasteners should not be loose or corroded. If you own a wood deck, you should clean and seal the boards every year. Check your deck yearly and before large gatherings for rot and other problems.
Because decks are exposed to the weather, they don't last forever, and they always come down with friends and family. So make sure your deck doesn’t come down unexpectedly.
President of Deck Builders, Inc
Professional Deck Builders Magazine
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