What's inside
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Contents
Choose a size and set the slope
This simple deck box has a plywood body, a framed lid that sheds rain, and no complicated joinery. A practical finished size is about 36 inches wide, 20 inches deep, and 22 inches tall at the front. That holds cushions or garden gear without making the box too heavy to move. Check your largest item before cutting; bulky seat cushions often need more inside clearance than their label suggests.
For a 20-inch-deep lid, make the back about 2 inches taller than the front. That gives a modest slope of roughly 6 degrees—enough for water to run off, but not so steep that the lid looks awkward. The dimensions below are a working example, not a fixed plan. Adjust the width or depth to suit your space, and keep the back-to-front height difference if you change the depth.
Materials and tools
Use exterior-rated plywood, not ordinary interior plywood, which can delaminate when exposed to damp weather. Half-inch plywood is adequate for a moderate-size box if you add corner cleats and a center support; 3/4-inch plywood is stiffer but heavier and costs more. For outdoor use, choose exterior paint or a penetrating exterior finish and seal every cut edge.
You’ll need exterior-rated plywood, straight 1-by-2 lumber for cleats and lid framing, exterior screws, waterproof wood glue, two hinges, and a lid stay or soft-close support. A circular saw with a guide, drill, square, tape measure, clamps, and a sanding block will cover the work. A search for exterior plywood can help compare available grades and sheet sizes; inspect the actual panel for flatness and voids before buying.
| Material choice | Good fit | Trade-off |
|---|---|---|
| 1/2-inch exterior plywood | Smaller box with cleats and a center support | Lighter and often cheaper, but edges dent more easily |
| 3/4-inch exterior plywood | Wider box or frequent heavy use | Stiffer, but adds weight and cost |
| Painted exterior finish | Color and better UV protection | Needs sound surface preparation and eventual repainting |
| Penetrating exterior finish | Visible wood grain and easier touch-ups | Usually needs more frequent maintenance |
Make the cut list
For a box about 36 inches wide by 20 inches deep, cut the front and back panels 36 inches wide. Make the front 20 inches tall and the back 22 inches tall. Cut two side panels 19 inches deep; their top edges should slope from 20 inches at the front to 22 inches at the back. This arrangement lets the front and back cover the side-panel edges. The exact finished width and depth will vary with plywood thickness and assembly layout, so dry-fit the pieces and measure before fastening.
For the lid, make a framed plywood panel that overhangs the body by about 1 inch on the sides and front. A lid roughly 38 by 21 inches is a reasonable starting point; leave a small gap at the back so the hinges can move freely. Cut the plywood top to size, then add 1-by-2 framing underneath. Test the lid against the assembled box before sealing or finishing it.
Assemble the box
Mark the sloped line on each side panel with a straightedge and cut it carefully. Clamp the panels before cutting; a wandering cut creates a gap that is hard to hide and can weaken the lid support. Sand the edges, then fasten the front and back to the sides using glue and exterior screws into 1-by-2 cleats at the inside corners. Predrill near plywood edges to reduce splitting, and keep screws far enough from the edge that they do not break through.
Fit the bottom inside the box, resting it on cleats or a continuous support strip. Use exterior plywood for the bottom too, and drill several 1/4-inch drainage holes near the corners. A sealed, watertight box can trap condensation and rain that gets past the lid, so drainage is useful even when the lid overhangs. Add a center support under the bottom if the box will hold heavy items or if the span feels springy.
Build and fit the lid
Glue and screw the 1-by-2 frame beneath the lid panel, keeping it square and flush with the panel edges. If the lid is wide, add a crosspiece to limit flex. Set the lid on the box and check that it sits evenly on the sloped rim. A warped lid or an uneven rim leaves a low spot where water can stand; correct the fit before installing the hinges.
Fasten two exterior-rated hinges to the back edge, spacing them several inches in from the ends. For a heavy lid, use three hinges or add a continuous hinge. A lid stay made for outdoor storage boxes reduces the chance of the lid falling on fingers. Do not rely on friction hinges alone to hold a heavy top open. Test the motion slowly, and check that the lid does not bind against the taller back panel.
Seal it and keep it usable
Sand exposed edges, fill screw holes if desired, and apply finish to all surfaces, including the underside of the lid and the inside faces. End grain and plywood edges absorb moisture fastest, so give them particular attention. Follow the finish label for drying time between coats; applying another coat too soon can leave a soft, tacky surface. Put the box on feet or thin plastic spacers rather than directly on a wet deck, and leave a little clearance beneath it for airflow.
Keep the lid light enough to lift safely, and add a child-resistant latch if children could climb inside. A lid stay is not a substitute for supervision. Recheck screws and finish after the first wet season; tighten loose hardware and touch up bare edges before water gets under the plywood veneer. If the box will sit fully exposed to rain year-round, a small roof or a fitted cover will extend its life more than extra decorative trim.