Recently a client asked me to replace the floor on her small back porch. At 3 feet wide, it was pretty useless for anything other than collecting stuff, so she wanted to increase the width by more than a foot, plus add a wavy outer edge that would meander around a large Rose O’Sharon shrub and mimic the winding curves of her cottage garden.
The customer chose 5/4 x 6 mahogany for the decking, which would provide some extra beef where the boards hung out past the band. But in order to get the cantilever, I would have to run the joists in the same direction as the decking, with horizontal blocking in between for support. I tried laying out the framing on 16-inch centers, which looked okay except for a couple of places where a joist landed directly under a gap in the flooring — a prime spot for dirt and debris to collect. I figured nothing was limiting me to a 16-inch layout, so I did a quick mockup with some decking scraps and adjusted the joist spacing to avoid this situation.
We installed a double ledger along the house, pitched slightly from the inside corner of the porch, and attached hangers for every joist. To visualize the curve, I set some plywood scraps on the foundation and then used a flexible rubber hose to get a rough idea of what the client had in mind. From there I knew how far to run the joists to support the projecting curve. To maintain an adequate slope away from the house, I had to notch some of the joists where they crossed the block foundation. Where the band joist stepped out for each section of the curve, I added 45-degree transitions between the projections, then finished off with PVC trim.
Next I rough-cut the boards to length and lined them up on top of the framing; the 16-13/16-inch layout worked out great. I then handed my client a piece of chalk and went out for coffee. When I returned, she had drawn the whimsical pattern she wanted without any meddling from me. We refined the curve on either side of the steps for a smooth transition, and I stacked the boards for installation. I cut the curved ends with a jigsaw, setting each successive piece in place to mark where the curve of the previous board ended. I eased the edges with a 3/16-inch roundover bit, then hand-sanded the end before screwing the board in place. I used 2-1/2-inch stainless finish head screws, predrilling for each one.
I reinstalled the original posts (which my client plans to replace eventually with driftwood logs). The drop-off on the open end of the porch was so slight that we could forego a guard rail, but I turned some of the flooring scraps into a decorative railing. I even had enough flooring left over to build a matching table. The porch is now wide enough for two people to sit on comfortably.
Roe Osborn is a carpenter and photographer on Cape Cod, Mass.