Secrets to successful outdoor woodwork

If you build outdoor furniture the same way you build indoor projects, you’re headed for grief. I know, because I’ve experienced plenty of heartache learning things the hard way. Finishes that don’t last, joints that fall apart and corrosion-stained surfaces are all common and disappointing fates that afflict outdoor furniture. Common, but not unavoidable—at least, not if you follow my field-proven design and construction tips.

Moisture and sunlight are the enemies that you must deal with at the start. Cedar is such a popular choice for outdoor projects because it keeps these foes at bay: it’s rot-resistant and long-lasting. Yet, cedar also has weaknesses. It’s particularly soft and structurally weak, which creates problems you must address when you build.

Cedar needs large, overlapping joint areas and a lot of help from fasteners and glue if it’s to hold together for the long haul outdoors. Avoid mortise-and-tenons and dowel joints. Even lap joints can fail unless they’re cut in extra thick wood.

Keeping your wood in good condition
Since cedar dents easily, I recommend you rout corners with a round­over or chamfer bit. Also, square edges don’t hold a finish as well as rounded or angled ones, and as your finish wears out at the corners, deterioration spreads to surrounding areas.

Leave any 3⁄4"-thick lumber outdoors for a couple of years and it’ll almost certainly develop a cupped shape across the width of the boards. This change happens as the wood gets sopping wet and then bone dry over the course of each year. That’s also why beefy lumber—thicker than 1"—is my choice for most outdoor applications. It’s much less likely to cup as it ages.

Large-diameter wood screws (I prefer #10) work best with cedar because the wood is so soft. But even these should be supplemented with weatherproof glue, and not just for strength. Ordinary wood glues—even those rated as water-resistant—go mushy during damp, outdoor weather. You need to use glues that meet the waterproof rating set by the American National Standards Institute (ANSI). For example, a glue that ANSI rates as Type II is suitable for outdoors. A Type I glue actually has a higher waterproof rating than Type II. So if you can, use Type I.