How to Build Planter Box with Legs | Build It Right

A planter box with legs raises plants to a comfortable working height while protecting wood from ground moisture; the build comes down to one weather-resistant frame with leg assemblies and drainage.

Building a planter box with legs solves two problems: better access without bending, and legs keep wood off damp ground where rot starts. Whether a simple raised bed on legs or a modern patio planter with storage, the same core method applies. Here’s how to build one that lasts.

The Basic Frame and Leg Assembly

Use weather-resistant lumber — treated pine, cedar, or any wood rated for outdoor exposure. The classic build uses 1×6 boards for sides and 2×2 or 2×4 stock for legs. Cut four side pieces to your desired length (common sizes range 24 to 48 inches), then attach legs 1 inch from each corner end using 3-inch exterior screws driven into the frame’s corners. This offset distributes load directly through the leg. For retro-style tapered legs tilting outward, use a 1×3 or scrap plywood ripped to 2½ inches wide and cut each leg with a 15-degree angle at top and bottom — Kreg’s modern planter plan uses this geometry for a clean mid-century look.

Add bottom supports: a 1×2 ledge screwed around the inside bottom, set so the panel or slats sit flush. This ledge carries all soil weight, so use deck screws rather than nails for the long side ledges.

Building the Bottom: Slats vs Solid Panel

Two options exist. A slatted bottom with six to eight boards spaced about ¾ inch apart optimizes drainage — water falls through, and gaps let air circulate. Fasten each slat to the ledge with one or two brad nails per side. A ¾-inch plywood bottom is sturdier for larger planters and supports heavy wet soil without sagging, but drill three or four 1-inch drainage holes ½ inch up from each end board to prevent water pooling. Whichever route, line the inside with landscape fabric before adding soil. The fabric holds dirt in while letting water escape and stops soil washing through gaps.

If you want extra utility, a lower shelf assembly transforms it into a storage planter. The Lowe’s storage planter design adds shelf slats and a door, creating space for potting soil bags and tools beneath the planting box.

Drainage, Lining, and the Mistakes That Kill Planters

Drainage is the single most important detail. Without it, roots rot and trapped moisture accelerates wood decay. Even a slatted bottom needs the landscape fabric trick — it breathes while stopping soil loss. When adding soil, leave 1 to 2 inches at the top; overfilled planters spill mud and leave no room for mulch.

Another common mistake is using untreated wood outdoors or skipping preservative. Unfinished cedar or redwood mellows to gray, which some prefer, but treated wood or quality exterior stain adds years. Wood expands and contracts with weather changes, so leave about 5mm (roughly 3/16 inch) between side boards if using multiple boards per side — Ryobi’s modern planter plan uses this spacing to let timber move without cracking the frame. For pre-built solutions, see our review of the best flower boxes on legs.

Finishing and Filling the Planter

Sand all edges with 120-grit paper, then soften corners with a router or by hand. Apply exterior stain or sealant — one coat for natural finish, two for deeper protection. Let it cure fully before adding soil. Use lightweight raised-bed mix rather than heavy garden soil; it drains better and is easier on the structure. Fill to within an inch of the top, plant, and water gently. The legs lift the assembly off the ground, keeping air circulating underneath and preventing rot that kills ground-set boxes in two seasons.