You know that moment—you sit down on a park bench in nice shoes, then go to stand up and your heel slips right through the gap between two wooden slats. It’s annoying, a little embarrassing, and sometimes it even scuffs the leather. So what’s the safe spacing to prevent that from happening?
Most outdoor bench manufacturers and landscape architects will tell you the magic number is no more than 1/2 inch (about 12–13 mm). That’s the typical maximum gap if you want to keep a standard high heel, wedge, or even a narrow dress shoe heel from dropping through.
Why 1/2 inch specifically? It comes down to the smallest common heel tip diameter. Many stiletto heels taper to roughly 3/8 inch at the bottom, but some are slightly wider or have a small cap. A 1/2 inch gap gives you a little buffer without looking overly tight. If you go up to 3/4 inch, you’ll start catching smaller heels regularly—especially in public spaces where people wear all kinds of footwear.
For residential outdoor benches, many DIY builders stick with a 3/8 inch (9–10 mm) gap between slats. That’s visually pleasing, still allows water to drain and air to circulate beneath cushions, and it’s nearly impossible for a heel to wedge through. It’s also a good choice if you have kids who like to climb on the bench—tiny fingers won’t get stuck either.
There’s another practical reason to keep gaps under 1/2 inch: building codes and accessibility guidelines. In the U.S., the ADA doesn’t specifically regulate bench slat spacing, but many public park standards reference the “1/2 inch rule” for any opening on seating surfaces to reduce pinch points and trip hazards. If you’re installing benches in a commercial or community space, sticking to 1/2 inch or less is the safe, code-friendly choice.
How do you measure it correctly? Don’t eyeball it. Cut a small spacer block from scrap wood or use a stack of washers to set the gap while screwing down slats. A 1/2-inch plywood strip works perfectly—place it between slats, tighten everything, then pull the strip out. Check your gaps in a few places along each joint, because wood can shift slightly as you work.
What if you already have a bench with wider gaps? You have a few easy fixes. Add narrow filler strips between the existing slats—e.g., 1/4-inch strips on each side of a 1-inch gap to reduce it to 1/2 inch. Or replace the slats with wider boards, which automatically reduces the number of gaps and tightens the spacing. A quick temporary fix is a thin outdoor rug or cushion, but that traps moisture and isn’t ideal long-term.
Bottom line: if you’re building or buying an outdoor bench and care about heel safety, aim for 3/8 inch to 1/2 inch maximum gap between slats. That range gives you drainage, comfort, and a sleek look without turning your bench into a shoe trap. Your heels—and your ankles—will thank you.