Over the past few weeks, I designed and built a set of custom cedar planter boxes for our yard. After replacing a small lawn area with stones, we wanted three freestanding flower boxes that could sit along one side of the yard and add some color back into the space.

Rather than build the boxes that directly hold the soil, I decided to use purchased plastic planter boxes as inserts and then design a custom cedar enclosure around them. This gave us the clean appearance of a custom-built wood planter while keeping the planting, drainage, and long-term maintenance simple.

The purchased plastic flower box became the starting point for the entire design. These inserts are designed to sit either directly on the ground or over a standard horizontal 2x6 or 2x8 beam. I liked that built-in support concept, so I decided to make a 2x6 cedar beam the primary structural element of my planter box. The beam supports the plastic inserts from below, ties the end assemblies together, and provides a strong center structure for the full box.

I began by modeling the plastic planter insert in xDesign so I could use it as an accurate reference for in-context design. This part was more challenging to model than it might look at first glance. It is a shelled injection-molded part with drafted side walls, rounded corners, a top flange, and a recessed underside that nests around the support beam. Because of those molded details, the most accurate way to recreate the part was with surface modeling techniques. I plan to cover that modeling process separately, but for this project the important point is that the insert model gave me a reliable core reference to build around.

The underside photo and section drawing show the main design relationship between the plastic inserts and the cedar beam. The 2x6 beam fits into the recessed area under the two plastic planters, allowing the inserts to sit securely while keeping the top of the plastic boxes aligned with the top of the wood enclosure. This relationship drove the height, internal supports, and overall construction strategy for the planter box.

Once the insert and beam relationship was established, I designed the wood structure around those components directly in the assembly. This is where xDesign was especially useful. Instead of creating a separate component for every individual board, I modeled the cedar structure as a single component with multiple solid bodies. Each wood board was its own body, but all of the wood geometry lived inside the top-level Design Features set of the assembly.

This workflow let me work quickly while still preserving the important benefits of a detailed model. I could visualize the final box, measure lengths and clearances, confirm fit around the plastic inserts, and create accurate drawings for fabrication. This made the workflow much easier than it would have been if every board had been created as an individual component.

To create each board, I used the Extrude command with the “New” option selected. This prevents the extrude from merging with existing geometry and creates a separate body instead. For this type of woodworking layout, that was important because each board needed its own selectable edges and faces. It also made the model easier to interpret visually, since the seams between boards remained visible.

My first design had the front and back boards overlapping the side boards. The goal was to cover the end grain of the side pieces and give the box a cleaner appearance. However, once I started laying out the cuts against standard 1x6 cedar stock, I realized that this arrangement was not the most efficient use of material.

That was an important turning point in the project. The design had to move beyond what looked good on screen and become something that could be built efficiently from the stock I planned to buy. Since I was making three planter boxes, material efficiency had a direct impact on cost, waste, and fabrication time.

Using cut list optimizer, I adjusted the board lengths to get the best yield from the cedar planks. To make the layout work, I reversed the overlap between the front/back boards and the side boards. That solved the material usage problem, but it reintroduced visible end grain at the corners. To address that, I added vertical leg face boards at all four corners. These boards improved the appearance, covered the end grain, added visual detail, and strengthened the corner construction. I also added small feet to raise the planter box approximately one inch off the ground.

The final design was based around ripping standard 1x6 cedar planks in half. This created boards approximately 2.66 inches wide, which became the common width for the front, back, side, internal support, leg face, and foot pieces. Keeping all of those pieces the same width simplified the fabrication process because I could rip all of the 1x6 stock to one consistent width before crosscutting the individual parts to length.

For the three planter boxes, I purchased eight 8-foot 1x6 cedar planks and two 8-foot 2x6 cedar beams. After crosscutting the stock in half, I ripped the 1x6 pieces in half to create the common stock used for all of the exterior boards. The purchased cedar boards already had rounded outside edges, which gave the boxes a softer finished appearance. After ripping the boards, the newly cut edges were sharp, so I used a router with a 1/4-inch roundover bit to give all exposed edges a consistent profile.

Before crosscutting the ripped boards to final length, I reviewed the stock and selected which pieces would be most visible. Boards with more attractive grain and knots were used for the front, back, and side faces. Cleaner, less visually interesting boards were reserved for internal supports and hidden structure. This helped make the finished boxes look better without requiring additional material.

The engineering drawings became my primary reference for fabrication. It defined each required part, including the front and back boards, side boards, internal supports, leg faces, feet, main beam, and beam supports. Having these drawings available in the shop made the cutting and assembly process much more controlled. Instead of measuring from the CAD model repeatedly, I could work directly from the drawing and part callouts.

I started the assembly by building the two end panels. Each end panel is made from three side boards and two internal support boards. The end panel drawing defined the spacing, offsets, and support locations. I used 3/4-inch plywood spacers between the side boards to maintain consistent gaps and lightly clamped the pieces together before fastening.

One detail that came directly from the CAD model was the chamfer on selected internal support boards. The angled lower walls of the plastic inserts interfered slightly with the end supports, so I cut a small chamfer on the top of those boards to provide clearance. This is a good example of why modeling the purchased insert accurately was useful. The interference was easy to see and resolve before final assembly.

During the early assembly stages, I used a brad nailer to tack the parts together. The brads made it easy to hold the boards in position while checking fit, squareness, and alignment. Once the end panels were assembled, I attached the first front board between the two side assemblies, then continued adding the remaining front and back boards. If anything was not right, I could pull the boards apart, reposition and nail them again.

After the outer box was tacked together, I test-fit the plastic inserts to make sure they sat correctly and that the clearances matched the CAD design. I then turned the unit over installed the main cedar beam and beam supports from the under side. The beam is one of the most important structural elements in the box because it supports the plastic planters and ties the assembly together from underneath. I glued the 4in support blocks to create more surface area between the structural beam and the sides.

The close-up corner photo shows the fastening strategy. The brads were only used to hold the boards during initial assembly. Once everything was aligned, I predrilled the joints and reinforced the construction with exterior-grade 2-inch screws. I drove screws from multiple directions around the perimeter so the front, back, side, and corner elements were locked together securely.

The final construction steps were attaching the leg face boards and the feet. The leg faces gave the corners a more finished look and helped hide the board overlap change that came from optimizing the cut layout. The feet lift the box slightly off the stone surface, which helps the planter feel more intentional and keeps the wood from sitting directly on the ground.

The finished planter boxes are made from white cedar, so they can be left unfinished outdoors. The removable plastic inserts make planting and maintenance easier, while the cedar enclosure gives the boxes a more custom, integrated appearance in the yard.

Overall, this was a simple but rewarding design-and-build project. The most interesting part was not just building the planter boxes, but connecting the full workflow from purchased part, to in-context CAD design, to material optimization, to shop drawings, to final fabrication. xDesign made it easy to combine assembly components with multi-body modeling so I could move quickly from concept to finished product.

I also included the 3DXML file at the end of the post so the design can be previewed or downloaded and opened in xDesign.