What's inside
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A wooden porch planter is a manageable weekend project for a beginner with a saw, drill, and a reasonably flat work surface. This design is a rectangular box with a separate slatted drainage base. The slats let excess water escape without requiring a full row of holes through the bottom, and the raised interior floor keeps the planter from sitting in a puddle.
The finished planter is approximately 36 inches long, 12 inches wide, and 12 inches high. Adjust the length to suit your porch, but keep the width and height close to these dimensions unless you are prepared to move a very heavy box. Wet soil adds far more weight than most first-time builders expect.
Contents
Materials and tools
Use naturally rot-resistant lumber such as cedar, redwood, or pressure-treated pine. Cedar is easier to work with and looks better unfinished, while pressure-treated pine costs less and lasts well outdoors. Avoid ordinary construction-grade spruce unless the planter will be fully protected from rain; it can begin rotting at the joints within a season or two.
- Two 1×12 boards, 36 inches long, for the front and back
- Two 1×12 boards, 12 inches long, for the ends
- Three or four 1×2 boards, 10 inches long, for interior cleats and feet
- Five or six 1×3 boards, 10 inches long, for the slatted drainage base
- Exterior-rated 2 1/2-inch screws
- Exterior-rated 1 1/4-inch screws
- Wood glue rated for exterior use
- Landscape fabric, potting mix, and a suitable finish
You will also need a tape measure, square, pencil, drill, countersink bit, clamps, and a saw. A box of exterior wood screws is worth buying instead of using indoor drywall screws, which rust quickly and can snap under outdoor movement.
Choose the right lumber
For the lowest maintenance, choose cedar or redwood and leave it unfinished so it weathers naturally. For the lowest cost, use pressure-treated pine, but allow freshly treated boards to dry before applying any finish. Buy the straightest boards available and reject pieces with large knots near the ends. A slight bow can be pulled into alignment with clamps; a twisted board usually makes the entire box look crooked.
| Lumber choice | Cost | Best use | Main trade-off |
|---|---|---|---|
| Cedar | Medium to high | Visible porch planters | Light, attractive, but dents easily |
| Pressure-treated pine | Low | Budget or utility planters | Heavy and may warp while drying |
| Redwood | High | Premium outdoor finish | Durable, but often expensive or hard to find |
Cut and prepare the parts
Cut the front and back boards to 36 inches and the end boards to 12 inches. These dimensions produce an outside length close to 36 inches when the end boards fit between the long boards. If your lumber is a true 1×12, it will be about 11 1/4 inches wide, not 12 inches. That is normal.
Cut four cleats to about 10 inches. Two will support the slatted base along the long sides, and two can be used as lower feet. If the planter will sit directly on a porch, add two or three feet underneath so air can circulate and water can dry beneath it. A small set of outdoor furniture feet can replace wooden feet, but simple scrap blocks are fine.
Sand the cut edges with 120-grit paper, then ease every exposed corner with two or three passes of the sandpaper. Sharp board corners are uncomfortable to handle and shed finish quickly.
Assemble the planter box
Stand one end board between the front and back boards. Apply a thin bead of exterior wood glue to the meeting edges, clamp the assembly square, and drive two screws through each long board into the end. Drill pilot holes first, especially near board ends, because cedar and pine can split.
Check the first corner with a square before adding the second end. Measure diagonally from corner to corner in both directions; the two measurements should be within about 1/8 inch. If they differ more, push the box into alignment before the glue sets. A planter that is slightly out of square will still function, but the drainage slats and finish trim will look uneven.
Build the slatted drainage base
Measure the inside length and width of the assembled box rather than relying on the cut list. Cut five or six 1×3 slats to fit across the width, leaving roughly 1/2 inch between each slat. These gaps provide drainage while still supporting the soil.
Install the two long cleats inside the planter, about 2 inches above the bottom edge. Use a level or measure up from each corner so the cleats sit at the same height. Drive screws through the side boards into the cleats. Set the slats across them and secure each slat with one screw at each end. Do not glue the slats in place; removable slats make it easier to clear trapped soil and inspect rot later.
For extra drainage, drill four or five 3/8-inch holes through the lowest part of each end board. This is useful on a porch exposed to heavy rain, but it is not a substitute for the raised slatted base. Water must have a clear path out, and the planter should never sit flat on a nonporous surface.
Line and finish the planter
Cover the inside with landscape fabric, letting it rest on the slats and rise a few inches up the sides. Trim excess fabric after filling. Do not use solid plastic unless you add generous drainage holes; a sealed liner can turn the planter into a waterlogged tub.
Use a penetrating exterior wood finish on the outside, including the bottom edges and end grain. Oil-based products usually deepen the color and shed water well, while water-based finishes dry faster and produce less odor. Finish all faces before assembly if you want the best coverage, then touch up the screw holes afterward.
Fill the box with quality potting mix rather than garden soil. Garden soil is dense, drains poorly in containers, and makes this already-heavy planter harder to move. Leave about 1 inch below the rim so watering does not wash soil over the sides.
Seasonal use and maintenance
Build in spring or early summer, when temperatures allow glue and finish to cure properly. In autumn, empty annuals and remove dead roots before repeated freezing. If you live where winters are severe, move the planter under cover or raise it farther off the porch; frozen, saturated soil can split boards and force joints apart.
Check the slats, cleats, and lower feet each spring. Soft wood, dark staining, or screws that no longer hold indicate moisture damage. Replacing a single slat is straightforward, but replacing a rotted cleat may require removing the soil and several drainage boards. Keep the planter at least slightly elevated, avoid constant contact with sprinklers, and recoat exposed wood when water stops beading on the surface.
For a different planting layout, place nursery pots inside the box instead of filling it. This reduces weight and makes seasonal changes easier, but it sacrifices some planting depth and still requires a drainage path beneath each pot.