How to Build Wood Planter Boxes Outdoor | Cedar, Drainage, Assembly

Build a durable outdoor wood planter box with cedar, galvanized screws, drainage gaps, and a landscape fabric liner.

Nothing sets off a porch or garden like a well-built wood planter. The right way to build one comes down to four things: rot-resistant lumber, rust-proof fasteners, proper drainage, and a liner that keeps soil from rotting the wood. A weekend of work gets you a box that lasts years instead of one season.

What Wood and Fasteners Work Best Outdoors

Cedar is the go-to choice for outdoor planters, and for good reason. Its natural oils resist rot and insect damage without any chemical treatment. Other options include redwood and pressure-treated pine—just remember pressure-treated wood should always be lined before adding soil.

For fasteners, skip the regular screws. Galvanized or exterior-grade screws resist the rust that plain steel develops when it meets damp soil and rain. Pre-drilling pilot holes before driving screws keeps cedar from splitting along the grain.

Cutting and Assembling the Frame

Start on a flat, level surface—a garage floor or patio slab works best. Cut four side panels from your 1×6 or 2×6 lumber, plus a bottom piece sized to fit inside the frame. The box’s overall size depends on what you’re growing: herbs thrive in a shallow 12-inch box, while tomatoes need at least 18 inches of depth for their roots.

Clamp the corners and drive your galvanized screws through the side panels into the corner boards. Attach the bottom supports—two short lengths of lumber running perpendicular to the bottom slats—before you drop the floor in place. This keeps the planter off the ground so water drains freely and air circulates underneath.

Adding Drainage and the Liner

Water needs an escape route or your plants will drown. Drill 1/2-inch holes every six inches across the bottom, or space your bottom slats with 1/4-inch gaps so excess moisture seeps out. Either method works; the key is making sure water never pools against the soil.

Line the interior with landscape fabric before adding soil. Cut a piece large enough to cover the bottom and all four sides, then staple it to the inside edges of the frame. This fabric lets water pass through while keeping soil from washing out and reduces the contact between damp dirt and the wood—the main cause of rot.

Finishing Touches That Extend the Life

Once assembled, seal the exterior with a weatherproof wood stain or exterior finish. Cedar takes a clear sealer well, while paint offers more protection if you don’t mind hiding the grain.

The most common mistakes boil down to skipping the pilot holes, using cheap fasteners, or forgetting the liner entirely. Each one shortens the planter’s life. Do all three right and you won’t need to rebuild for a long while.

Before you start cutting, it’s worth seeing tested outdoor wood planter boxes worth buying if a DIY build isn’t your speed.

FAQs

Is cedar worth the extra cost over pine?

Yes, if you want the planter to last. Cedar’s natural rot resistance means it can survive outdoor conditions for a decade or more without chemical treatment. Pine rots within a few years unless you pressure-treat it or commit to regular sealing, which makes cedar the better long-term value.

Do I need to drill holes in the bottom of a wooden planter?

Yes. Without drainage holes or gaps, water saturates the soil and rots the roots of most plants. Drill 1/2-inch holes every six inches or space the bottom slats with quarter-inch gaps. Elevating the box slightly with feet lets the water escape instead of pooling underneath.

Can I paint a wood planter instead of staining it?

You can, but paint traps moisture against the wood and can peel within a year or two. A breathable exterior stain or sealer lets the wood release moisture while still protecting it from rain and sun. If you prefer paint, use an exterior-grade primer and finish, and expect to touch it up regularly.