Several plans for planter boxes made from pallets already exist on Instructables, so I'm probably adding another brick to a wall that can't get any higher. In any case, I hope my take on a pallet planter box will inspire some of you. This plan outlines my project, though I identify areas where builders can opt for different routes.

The garden box I make here will be about 20 inches tall and 13 inches wide.

To make the planter box, you will need

Pallets
A table saw or saber saw
Perhaps a reciprocating saw
A circular saw
Screws or nails and/or a nail gun
Landscape fabric, 6 mil plastic, or tar paper.
Perhaps paint that restores old wood and fills in cracks
Perhaps caulk rated for exterior use
Safety goggles

Before you begin, please read this instructable, How to Determine if your Pallet is Safe for Use, especially if you plan to house vegetables in the planter box.

Step 1: Step One: Dismantle Pallets

Several instructable explain how to dismantle pallets to harvest the wood and possibly the nails. Here, I am providing my take on the process.

To dismantle the pallets, use a 10" or 12" extra-thick demolition blade on my reciprocating saw. Longer blades allow for leverage needed to work in between the boards. When dismantling the pallets, decide whether or not to remove nails and screws. It is a good idea to remove them if they may get in the way of cutting them to size. The builders decide whether they would like to remove the fasteners.

Pulling pallets apart with a pry bar can be tricky, as the wood is often brittle and can splinter. It's a good option for those who want to save and reuse the nails, though. Some people saw off the ends of the wood and only pry from the center, but then they are losing 3-4 inches of good wood.

After I dismantle the pallets, I like to sort the wood.

Step 2: Step Two: Cut the Frame and Side Panel Wood

Standard pallets are just under 40 inches wide, so cut the side panel boards (the fat exterior boards that people will see) at 39 3/4 inches or so. A jig will help make the process faster. A 36-inch long by 13-inch wide by 20-inch tall planter box will consume just over one pallet's worth of planks.

Save boards that are cracked, crooked, or bark-edged. The good sides of those boards can be used if a board has to be ripped to width. Additionally, those boards might have a good ten inches or so that can be used for the bottom of the box. If several boards only have about 12 inches of good material, then you may want to use them on the sides of the box, horizontally.

To create the internal framing, rip the 2x4-ish wood to 2 x 2-ish wood. The internal framing for hollow-core interior doors is a good alternative for these pieces.

Measure the width of the pallet wood to get a general idea of how wide it is. If plans call for a 36-inch long planter box and the boards are 5/8 inch thick, for example, cut the long internal frame pieces 1 1/4 inch short (5/8 + 5/8 = 1 1/4), or 34 3/4 inches, to ensure the box is the proper width.

Likewise, if the plans call for a planter box that is 12-inches deep, then subtract the width of the long framing and the side panel boards from the length. Since I am making a series of planter boxes for my yard, I decided that they all will be about 20 inches tall and about 13 inches wide. So I cut all of my short framing pieces to about 10 inches. That measurement will come in handy in a few steps.

Think ahead and consider the rim or lip of the planter box and include that in measurements if size must be exact.

Step 3: Step Three: Build the Internal Frame and Attach Side Panel Boards

When creating the two internal frame pieces, the front and back parts should be the long parts. That way, the outer side panel boards will be nailed or screwed to both the side frame and front frame, which should increase strength.

I screw the frame pieces together with 3 1/2 inch deck screws and pre-drill the holes. They could be nailed or air nailed, as well. I only put one screw into each joint, which makes it easier to manipulate and square the frames. The side panel boards will provide any needed strength.

The top of the planter will have a rim, so consider attaching the side panel boards with the uncut or crooked or ugly side up so any of those bits can be covered by the rim and so the exposed bottom edge will look clean. A glance at the photo will reveal that I didn't follow my own advice. Most of my boxes will sit on railroad ties or bricks, so a clean bottom edge isn't too important for me. I ensure the top edge is straight so the rim isn't crooked.

If using screws or nails larger than trim nails, consider pre-drilling nail holes. Otherwise, the wood may crack.

Lay out the boards before attaching them. Try different widths to see if they can be attached without ripping any to width.

Once the side panel boards have been attached, be sure to square the frame by taking diagonal measurements.

Step 4: Step Four: Attach Panels to Front and Back and Clear Nail or Screw Tips

Attach the front and back panels to the frame. Again, lay the boards out ahead of time, as the correct combinations of widths can eliminate the need to rip any boards to width. If any boards must be ripped to width, set them on the frame and trace the cut line. If the line is not straight, use a saber saw to cut the board to width.

Since I attach the side boards with a nail gun and don't worry about nail length, the nails stick through the frame boards. They can cut gardener's wrists, so I remove the nubs with an angle grinder. A reciprocating saw or a pair or wire cutters could also remove them.

Step 5: Step Five: Add a Rim and a Bottom

Cedar fence is a great planter box rim material. Since the frame boards are under 2" wide and the pallet boards are under 3/4" wide, a fence board ripped in half will make for a great rim.

The rim on the planter box pictured is 2 3/4 inches wide. It can be made of pallet wood or fence wood. If two pieces must be used to make up one edge, then consider cutting the joint on an angle. In addition to nailing the rim on from the top, consider nailing the corners together from the sides to prevent curling or separation.

If I measured the frame correctly, the inside of the planter box should be about 12 inches wide. Since the frame boards are 1bout 1 1/2 inches wide, I can cut bottom pieces at 10-12 inches, so one pallet board could make four bottom pieces.

There are options for the bottom. Some people like to put potted plants inside planter boxes. If that is the case for your project, then you could use any boards, no matter how crooked, bent, or cracked, or no boards. Since I am filling my boxes with dirt, I use mostly straight wood. I'll actually use whatever scraps I have laying around.

Step 6: Step Six: Finishing Details

If the planter box is over 30 inches long, it's a good idea to attach an additional frame piece to the middle of the box. In the final picture above, I added a tree branch that ensures the box will not bow out and provides an easy carrying handle.

As the pictures indicate, I wrapped the inside of the planter box with tar paper. I did that for this box because I do not plan on planting vegetables in the box because tar paper can leech chemicals into the soil. When I make boxes that will hold edible plants, I line them with 6 mil plastic. No matter the liner, I measure it so it covers the sides and then overlaps on the bottom. Excess water should have an exit route and the liner should prevent dirt from escaping the sides.

At this point, the planter box is basically finished. However, builders could opt for more finishing details. Clear finish would make this box look fantastic, and that look is quite popular these days.

My wife desires a uniform back yard, so the color scheme calls for chocolate brown planter boxes. Since I am painting the boxes, I go ahead and caulk the seams. I also use restorative paint that can fill cracks. The caulk and paint combination creates