Build Your Own Cedar Planter Box in One Afternoon (Step by Step)

A good cedar planter box works on a patio, a front porch, a balcony (check weight capacity first), or a driveway edge. It gives you a raised garden anywhere you have 6+ hours of sun. And unlike buying one, building it yourself means you can size it to exactly fit the spot you have. Let's build one.

One 8-foot cedar 1x8 board (about $18-$25). One 8-foot cedar 1x2 board for internal cleats and trim (about $6-$8). One 8-foot cedar 2x2 for corner posts (about $8-$10). A box of exterior-grade 1.5-inch screws (about $8). One small square of plywood for the base (about $6, or use scrap). Wood glue if you want extra strength (optional, $4). Total: about $50-$60 for materials. Add $10-$15 if you want an oil finish.

A drill or driver with a countersink bit is ideal but not required. A tape measure. A pencil. A speed square or combination square. A miter saw or a hand saw for cutting. Optional but nice: a random-orbit sander. If you don't own a saw, most home improvement stores will make cuts to your list for free at purchase — bring the cut list below.

"A drill or driver with a countersink bit is ideal but not required."

Cedar 1x8: cut four pieces at 24 inches (short side panels — two per side means two sides). Wait, let me clarify: cut eight pieces at 24 inches long. Two 1x8s stacked make each side of the planter 15 inches tall (two 7.25-inch-wide boards). Cedar 2x2: cut four pieces at 20 inches (corner posts). Cedar 1x2: cut four pieces at 24 inches (top trim). Plywood: cut one piece 22 x 22 inches (base).

For each of the four sides, take two 24-inch 1x8 boards. Lay them side by side (long edges touching) on your work surface — this forms one 15-inch-tall panel by 24 inches wide. Attach them together at the edges to the 2x2 corner posts (see next step). This is much easier than trying to hold everything together at once.

Stand one 20-inch 2x2 corner post upright on your work surface. Place one of your 24-inch 1x8 boards flat against it, with the bottom edges aligned. Predrill and drive 1.5-inch exterior screws through the 1x8 into the 2x2, spacing screws every 4-5 inches. Repeat with the second 1x8 stacked directly above the first, so the two boards together cover the length of the 2x2 post. Now you have one corner post with one side attached.

"Stand one 20-inch 2x2 corner post upright on your work surface."

Attach the adjacent side to the same corner post at a 90-degree angle. Then continue adding sides and posts until you've built a rectangular box with four corner posts on the inside and eight 1x8s forming the walls. Check that the box is square by measuring the diagonals — both diagonals should be equal. Small adjustments before the screws are fully tightened keep everything true.

The base needs drainage. Take the 22x22 piece of plywood, drill six to eight ½-inch drainage holes through it, and set it inside the box, resting on the bottom edges of the corner posts. Add small cleats (short pieces of 1x2) screwed to the inside walls of the box at the right height to support the base. Alternatively, screw the base directly to the bottom of the corner posts from below. Either method works — the goal is a base that supports soil weight and drains freely.

The 24-inch 1x2 pieces attach to the top rim of the box, one along each side. Miter the corners at 45 degrees for a finished look, or just butt them together. This trim hides the top edges of the 1x8s and gives the planter a polished, professional appearance. Screw down from the top through the 1x2 into the top of each side panel.

"The 24-inch 1x2 pieces attach to the top rim of the box, one along each side."

Sand all outer surfaces with 120 grit then 220 grit sandpaper. Ease any sharp edges. Cedar can be left completely unfinished — it'll age to a beautiful silvery gray over 1-2 years. If you want to preserve the warm reddish tone longer, apply one coat of exterior-grade UV-protective oil like Penofin or teak oil. Avoid varnish or paint on cedar; they trap moisture.

Add a layer of landscape fabric on top of the base (optional but nice — keeps soil from washing through the drainage holes). Fill with a good raised bed soil mix or container potting mix. Don't fill with garden dirt — it compacts and drains poorly in containers. For a 24x24x15 planter, you need about 3-4 cubic feet of soil, or roughly 4-5 bags of potting mix at $6-$8 each. Total soil cost: about $25-$40.

This size planter is perfect for one large plant like a determinate tomato or a pepper plant with basil around it, or a mix of herbs, or a shallow-rooted flower display (petunias, calibrachoa, alyssum, dwarf snapdragons). For edibles, choose plants with root systems under 15 inches deep. Larger plants (indeterminate tomatoes, deep-root shrubs) need bigger boxes.

"This size planter is perfect for one large plant like a determinate tomato or a pepper plant with basil around it, or a mix of herbs, or a shallow-rooted flower display (petunias, calibrachoa, alyssum, dwarf snapdragons)."

Choose a spot with 6+ hours of sun for edibles. Any light for a decorative or shade-tolerant plant. Level ground is best; the planter's weight when filled and watered can be 100-150 pounds. On a wooden deck, use pot feet to lift the planter slightly for drainage and air circulation, which prevents damaging the deck below.

Same techniques scale up or down. A 24 x 48 x 20 planter for a small salad garden. A 12 x 12 x 14 planter for a single herb or flower on a small patio. A shallow 30 x 12 x 8 window-box-style planter for a deck rail. Once you understand the corner-post construction, you can build almost any size.

Cedar naturally resists rot and insects. Reapply oil (if you use it) every 1-2 years. Empty the soil every 3 years and check the interior for wear; refresh with fresh soil. Any single board that starts to look worn can be replaced individually — that's the beauty of screwed construction. This planter can easily last a decade with almost no fuss.

"Cedar naturally resists rot and insects."

The best part of building your own planter isn't the money you saved (though it's real — a similar-sized cedar planter retails for $200-$400). It's the small pride of walking past it every day and knowing your hands made it. A few years from now, the wood will have silvered, the plants will be lush, and you'll still remember the Saturday afternoon it came together. That's the real gift of DIY — a home built one honest project at a time.