8 Ways to Make an Old Deck Safe
Three days of strategic work and an investment in materials save this deck from a catastrophic ending.
I was at a client’s house only to estimate a front-door replacement, but my eyes were drawn to the second-story deck. From a distance, I could see that the joists on this old deck weren’t supported by a regular beam but were attached to a single rim joist that in turn was nailed only to the side of the 4×4 posts. A closer inspection revealed many other problems: corroding hardware; missing hardware nails; inadequate ledger attachment and flashing; stair stringers pulling away from the frame; and loose, warped guard balusters.
I wasn’t surprised. The houses in the neighborhood were built in the 1970s, and the decks were slapped on without attention to good building practices. There had been local cases of deck collapses. Without preemptive repairs, this deck was a catastrophe waiting to happen.
According to the North American Deck and Railing Association, more than 40 million decks are over 20 years old. You have to wonder how well those decks were constructed before model building codes ramped up minimum standards, not to mention the wear and tear nature inflicts on a deck year after year.
As it turned out, this old deck was worth saving. The framing was solid, and repairs were straightforward because I had easy access to the deck’s underside. I figured it would take only three days of labor and $600 in materials, much cheaper than dismantling and disposing of an old deck and building a new one. I used the American Wood Council’s Prescriptive Residential Wood Deck Construction Guide (also known as the DCA-6), based on the 2009 IRC, as a reference.
Problem #1: Shallow footings
|Starting at ground level, the first thing I noticed was that the footings appeared tilted and that the posts were sliding off the tops. I dug around a couple of footings and found that they didn’t extend below the frost line. Combined with their mushroom-shaped tops and unstable surrounding soil, their shallow depth had led to frost heave.
Problem #2: Posts don’t support the beam
|The single rim joist carrying the deck joists was face-nailed to the 4×4 posts, which extend up to become railing posts. Without additional support, nails have the potential to pull out. Ideally, the rim beam should be doubled and should rest directly on top of the support posts.
Problem #3: Unsecure ledger
|The ledger is inadequately attached to the house with washerless 5/16-in. lag screws and a few randomly driven structural screws. In addition, all the joist hangers are beginning to rust and are missing nails. Where there are nails, they’re the wrong type (6d common nails and 2-in. roofing nails).
Problem #4: No lateral load connectors
Lateral load connections have been prescriptively addressed in the code only since 2007. While not required on existing decks, they’re a well-advised upgrade to elevated decks. The lateral connection joins a deck joist to a joist inside the house. Two connections per deck are all that’s needed. After running the bolt or rod from the inside out through the ledger, position the deck-joist hardware and screw it in place. Add a bead of sealant to waterproof any gap between the rod and ledger.
Problem #5: Leaky flashing
|The thin aluminum ledger flashing is inadequate and is corroded in several spots. Left as is, the flashing will allow water behind the ledger, which in turn will cause rot and a potential deck failure. A more robust flashing system should include self-adhering membrane and flashing with a taller wall leg.
Problem #6: Broken balusters
|The spaces between most of the guard balusters are greater than the code limit of less than 4 in. Several balusters are warped or broken, and most are loose, attached only by a single nail at each end.
Problem #7: Unsafe handrail
Problem #8: Weak stairs
After a quick inspection, I found a handful of problems with the stairs. The tops of the stringers had pulled away from the header. The stringer cuts extended past the notches into the structural area. (The DCA-6 requires an uncut structural area of at least 5 in.) The stringer’s span was too long and spaced too wide without intermediate support. Finally, the stringer header itself had no supporting jacks and was nailed only to the posts.
—Mike Guertin is a builder in East Greenwich, R.I., and editorial adviser to Fine Homebuilding. His website is mikeguertin.com. Photos by Charles Bickford, except where noted.