What exactly are deck extensions? They’re just what they sound like: added sections of decking supported by part of the existing structure. You have a few installation options. If you have a slab patio, you can restyle it as a deck, or you can add a new section onto your old deck, going either one step up or one step down, depending on the design of your outdoor area. Whichever method you choose, make sure you have a deck plan before you get started.
Turn a Slab Patio into a Deck
If your existing concrete patio isn’t powdery or broken into chunks, you can easily install sleepers and then lay down decking in a weekend. Sleepers are 2x4 joists that sit on a solid surface rather than other boards—in this case, elevating the decking over the concrete. (Make sure to choose pressure-treated wood.) On the surface of the slab, snap chalk lines 16 inches apart on center, then install the 2x4s flat. Fasten them to the concrete with masonry nails or a powder-actuated tool. Cut and install the decking. Consider patterns other than parallel decking—the flat 2x4s provide a sufficient nailing surface for many formations, including the chevron pattern shown above.
Framing Step-Up Deck Extensions
To frame an extension one step up from the existing deck, lay out the post locations, then cut them to a height that allows the joists to rest on the surface of the old deck. Build the frame and toenail it to the old deck. Design your extension using 2x6s, if possible. That way, you’ll have about a 7-inch step up to the new deck.
Framing Step-Down Deck Extensions
To frame a step-down deck extension, use the edge of the existing structure as a ledger for the new frame. Mark the joist locations along this board, and lay out the site with batter boards and mason’s lines. Hang the joists in joist hangers.
