How To Build A DIY Modern Raised Planter Box

August 15, 2018 Johnny Brooke

I built these simple yet beautiful modern planter boxes using Cedar from the home center and a few pieces of angle iron. I do have detailed plans available for this project here, which include a materials list, cut list, and SketchUp file.

📦 Materials Used On The Planter Boxes (affiliate):

🛠 Tools Used On The Planter Boxes (affiliate):

DIY Modern Planter Box Plans

The Modern Planter Box plans include a 11-page detailed PDF document, including a detailed cutlist. The plans also include a SketchUp file (upon request) so that you can adjust the model to fit your needs. If you have any questions during the build, you can email me and I’ll do my best to help.

Step 1: Material Prep

The first step in this project was to break down the Cedar boards into their final lengths. This build is made of Cedar 1x4s, 1x2s, and pressure treated Pine 2x6s. Cutting the boards to length could be done with a circular saw, but I used my miter saw with a stop block and it made things super fast.

After breaking down the Cedar boards, I could start assembling the panels which make up the sides of the planter boxes. The short panels are made up of four of the 1x4 pieces and two of the 1x2 pieces.

Step 2: Assembling Panels

First, I marked up 1 ½” from the bottom edge of the bottom board, which will indicate where I need to leave the gap for the 2x6s which will be added later. Next, I squared up all of the boards and laid out the 1x2 pieces. One of the pieces is just used to figure out the spacing, as these panels lock together by having this offset in the corners.

With the 1x2 spacer in place, I added glue where the other 1x2 would be attached, used some ⅛” spacers to set the distance between the boards, and then attached the 1x2 to the 1x4 behind it with some 1” brad nails.

As you can see, I’m using a t-square to make sure things are nice and square during this process, and this is extremely important. I just kept working my way up the panel, using the ⅛” spacers between each board, and then repeated the process on the other end of the panel.

After getting building each panel, I went back and reinforced them with some 1 ¼” screws. This really made the panels a lot sturdier and should help them to hold up much better in the elements.

Step 3: Long Panels

I was making two of these planter boxes, so next I repeated the process three more times to get my other short side panels, and then I could move on to making the long side panels.

These panels are built in the exact same way, first attaching the 1x2s with glue and brad nails, then reinforcing them with screws. The only difference with these longer panels in the extra upright support in the center of the panel, just to keep the boards from flexing under the weight of the soil and plants.

One thing I should also mention is that the 1x2 pieces should roughly line up with the top board. If it does, this will ensure that your panels are all the same size.

Step 4: Joining Panels Together

Once all of the panels were put together, I could start assembling them into the planter boxes. You can see here how the 1x2s contact each other in the corners, creating something along the lines of a lock rabbet joint in each corner. I also made sure to assemble the panels with the top edge resting on my workbench, to make sure the top edges all lined up.

To make sure the connection between the corners was tight, I clamped them together, making sure any gaps were removed, and then I could add some 2” screws through the short side panels into the 1x2 of the long panel. I only added one screw at each corner at this point, so that the panels could still pivot so I could still snug up the other end of the panels.

Next, I flipped the planter box over, clamped the top ends of the panels together, and then added more screws. The screws should be about 1 ⅛” in from the corner of the planter box, to make sure they connect with the 1x2 from the other panel.

Step 5: Adding the Bottom

With the outer walls of the planter box attached, I could go ahead and get to work on the bottom. The bottom is made up of 2x6 pieces, and first I measured to confirm the length of the pieces I needed.

Over at the miter saw station, I could go ahead and cut the boards to length, making sure to clean up that factory end on the first board.

The bottom pieces are attached to the panels with pocket screws, so I went ahead and drilled three pocket holes into the end of each board. Getting the settings worked out here were a little tricky, but I eventually landed on having the jig set to the 1 ⅜” setting and the depth stop collar on the bit set a little bit deeper than 1 ½”.

To install the bottom boards, I just lined up the bottom edge of the 2x6 with the bottom edge of the panel, clamped it in place, then drove in a few 1 ¼” pocket screws. On this first board, I used these pocket hole clamps, but they actually left dents in the Cedar, so I switched to parallel clamps for the rest of the boards.

With one board installed and my jig settings dialed in, I could drill pocket holes in the rest of the boards. This pressure treated lumber was so wet that it was clogging up the bit, but I got through it, it just made a mess.

Once all of the pocket holes were drilled, I could install the rest of the bottom boards. As you can see, there is a roughly 1 ¼” gap between each of the boards to allow for drainage. You don’t need to go nuts trying to get this measurement precise, since it doesn’t really matter. I just worked my way in from the ends, leaving a small gap and clamping the boards in place while I drove in the screws.

Step 6: Adding Trim

The last wooden pieces to add to the planter boxes were the trim around the top edges, but first I sanded all of the corners flush before doing that, to make sure the trim was seated well.

Next, I measured my actual final length, about 47 ½”, and then moved over to the miter saw to cut the angles. This is one area where using a circular saw would be really difficult, as you don’t have a lot of surface to rest the saw on, so I’d definitely recommend a miter saw here.

To cut the trim, I first cut a 45 degree miter on one end, then flipped the board around, marked my length, and cut an opposing 45 degree miter on the other end. I always leave these pieces long at first, and then trim them to final size based on the actual dimensions.

After getting one piece to the right length, I used it as a template for the second long piece of trim, which you see me doing here.

With both of the long pieces cut to size, I attached them to the planter box with glue and 1 ½” brad nails. The 1x2 uprights were a great spot to drive in nails here. I also made sure the edges of the 1x2s were flush with the outside of the panels.

Once the long trim pieces were installed, I measured the length for the short trim pieces and cut them in the same way over at the miter saw.

This is the fit you want, with the edge of the 1x2 flush with the panel. Also, it looks like there is a gap in the miter here, but the pieces are slightly different thicknesses. If you work with these kinds of Cedar boards, you’ll notice all kinds of inconsistencies like this, but luckily it’s nothing a little sanding can’t fix.

Step 7: Lining the Planter

Speaking of which, with all of the wooden pieces installed, I could go ahead and give the outside of the planter box a good sanding with 80 grit sandpaper. The key areas to focus on here are the corners, which you want perfectly flush, as well as the trim. I also made sure to round over the corners, as the angle iron I used for the legs has a rounded inside corner.

After sanding, it was time to make this box ready for some planting. First, I lined the bottom with some galvanized steel mesh, to keep dirt from falling out of the gaps in the bottom if the plastic breaks. I picked up these tips from a planter box video Ben over at Homemade Modern did, make sure to go check that video out as well as his design looked awesome, as always with Ben.

I used some aviation snips to cut the mesh to size, formed it to fit the bottom of the planter, and then stapled it into place with ½” staples. I did cut away the areas where the mesh came into contact with the 1x2 uprights, so that the mesh could lay flat.

I repeated this process on the other half of the planter off camera, making sure the mesh overlapped in the middle, and then I could add some plastic to line the planter. I used 2mil plastic drop cloth here, which wasn’t as thick as I wanted it to be, so I doubled it up to make sure the plastic didn’t break under the weight of all the soil, and then stapled it into place. After installing the plastic, I punched some holes through it with a screwdriver for drainage.

Step 8: Steel Legs

The last step in this build was the legs, which I made from steel 2” angle iron. Since I used steel here, I cut down the pieces on my metal chop saw, but you could also use aluminum angle and cut it on a regular miter saw. You could also get the angle iron from a steel yard and they would cut the pieces to size for you.

I set up a quick stop block to cut the pieces to length, as it’s super important that they all match perfectly.

After cutting the pieces to length, I rounded over all of the sharp edges using my belt grinder, but an angle grinder and flap disc would work great as well.

Step 9: Legs Continued

Next, I needed to drill the holes for the screws I used to attach the legs to the planter boxes. I wanted all of these holes to line up nicely, so I marked them all out on the inside faces of the angle iron. One tip here, I love these paint pens for marking on steel. They show up much better than Sharpie and the paint is removed easily with a little Acetone.

With all of the hole locations marked, I drilled the holes over at the drill press, making sure to use cutting fluid to keep my drill bit from getting too hot.

Once all of the holes were drilled, I wiped all of the pieces down with Acetone to remove the paint pen, cutting fluid, and any other surface contaminants, and then sprayed on a few coats of flat black enamel paint.

Step 10: Finishing Up

After letting the paint dry, I attached the legs to the corners of the planter boxes using construction adhesive and screws. I used 1 ¼” screws for the two upper holes but could use 2 ½” screws on the lower holes since the hole ran into those 2x6 bottom pieces.

One thing to look out for here is there might be a screw underneath some of the holes, depending on where you put the screws through the corners of the panels before. Also, I probably should have pre-drilled these holes, as I got a little splitting.

The last little detail on this build was to use the same flat black spray paint to touch up the screw heads and make them match the legs, then I could get the planter boxes filled. Luckily, my mom was in town when I built these planter boxes and she’s a master gardener, so we bought a bunch of plants and soil to fill up the boxes and got them looking really nice.

And with the plants added, these planter boxes were done!