No matter which design you decide to build, you will need to answer a few questions.
Where will it go?
How big do you want it?
What kind of wood should I use?
The answers to these questions affect how you get started. For example: you will need to draw up plans and the location could affect how the base is built. Will it stand on legs or be sunk into the ground some? Will you need to dig out some dirt so you can set it into a hill? Next, you will need to know how much wood and materials you will need to find. For small boxes you may be able to recycle products around your house. And finally, the wood choice. Obviously, if you are recycling you are limited in your choice, but if not, you will want something that will resist rotting. Preferably something that isn't chemically treated like pressure-treated pine. This is why cedar is a common choice, but no matter what wood you choose, you can seal it with natural oils to gain some more time out of your box.
The following are the steps to make a simple, budget friendly, planter box from cedar fence planks.
9 Cedar Fence Planks
1 8ft 2x4
tung oil (optional)
Start by preparing your boards. To do this you want to rip your 2x4 in half long ways to end up with what are roughly 2x2s. Cut these into sections of the following lengths:
2 @ 36"
2 @ 13"
4 @ 10"
4 @ 6"
These will be used to frame and support the planter box.
6 @ 36"
6 @ 17.25"
Make sure to use as few planks as possible to achieve these boards. Break the table saw back out and cut a plank in half at 45 degrees and cut those sections to 18" each. You will need 8 total of those. You should have 1 plank left at this point. Cut it in half at 90 degrees and cut each of these on the miter saw to the lengths of:
2 @ 38.75
2 @ 19.5" with a 45 degree angle on the ends imagining you will be making a picture frame with them.
Next, you want to assemble the base. To do this, take two 36" 2x2s and put two 13" 2x2s between them to make a rectangle roughly 36" x 16". A single screw in each corner is all you need. As the rest of the box is assembled you'll be surprised at how strong and tied together everything starts to feel. Make sure to predrill all screw holes throughout the process; these boards are all relatively small so cracking could be an issue.
Building the floor of your planter box:
Take the 6 planks you cut to 16.25" and attach them to the back to create a little floor. I would recommend using at least one screw in each corner of each plank, so 24 total. This will help prevent the base from moving and will keep the boards flat. On the two end pieces you may add a 5th screw on the side to hold the small 2x2 to the base.
Next, attach the four 10" 2x2s to each corner to support the future walls. If you're running short on long screws, a toenailed screw on a couple of sides will work.However, for simplicity, a long screw up through the bottom works best.
With the frame set up it is time to place the siding. Take the six 36" planks and the six 17.25" planks and attach them to the sides of your frame starting flush at the top of the 2x2s and overhanging the bottom. Then come back with the four 6" 2x2s and attach them in the corners of your overhang as legs.
Now you should have what looks like a planter box but it needs some finishing touches. Take the eight 18" pieces you cut with a 45-degree bevel on one side and use these as trim for the corners. These won't need much to hold on, as they are primarily aesthetic- you may even switch to a small brad nailer to give the box a more finished look.
Finally, to tie it all together, take your 4 remaining boards, the ones you ripped in half on the table saw, and cut to 38.75" and 19.5" and create that picture frame around the top of the planter box. This should help to tie everything together and give it the finished look you desire.
The last step is optional but if you want to squeeze as much time as possible out of this box, you may want to go buy some tung oil. Use it to seal the exposed 2x4's, including the feet. This will help keep those pieces that are holding everything together from falling apart.
Check out this video for more details on this build and remember, there are endless options on how you build your DIY planter box!