This is an easy project that can be built in an hour or two using material reclaimed from a single pallet or several pallet tops. Used to secure the tops of palleted material like cardboard or crushed metal for recycling, pallet tops can sometimes be found with regular pallets, especially in places that have a lot of them. I was fortunate enough to salvage several dozen of them from a huge lot full of pallets that the owner wanted to get rid of. Pallet tops contain less material than a standard pallet but the wood is thinner, which is better for certain kinds of projects. Figure 1 shows part of my pallet top collection.
Step 1: Prepare the Wood
If you have some prepared pallet wood you are ready to get started. If not, choose your pallet (or pallet tops if you can get a hold of some) and separate the boards using a hammer and prying device (pry bar or large screw driver). De-nail (or de-staple, as the case may be) the wood. The combination of a claw hammer and a pair of pliers is sufficient to remove the nails or staples from the boards once you have disassembled your pallet.
If the wood is dirty form being kept outside, hose it down and sweep it off with a broom and let it dry (Figure 2). You can plane or sand the wood if you like, but the wood I used was from some pretty old (vintage!) source material and I preferred the rougher more primitive look for this project.
Step 2: Measure and Plan
The sill where this shelf was going was 58 inches long (Figure 3), so the shelf was designed to be 57 inches long to allow sufficient clearance on the ends to make installation easy. Since my boards were not 57 inches long, I decided to make a joint in the center of the shelf and butt the boards together in the middle. For good support and a balanced appearance I used five pieces of wood to support the shelf boards.
Note: If your window sill is not that long, say 48 inches or less, you can use fewer support boards (three or four) underneath. Or, you may have to use more than five if it is a really long sill. As a general rule, the support boards should be 14-18 inches apart.
For a shelf that is somewhere between 9-15 inches wide, you can use three pallet boards placed side by side to form the shelf platform. Pallet board widths vary. I wouldn't want to go more than 12-14 inches wide without using some additional bracing from the wall underneath to provide added support. To keep construction simple, rip cut the boards as needed to keep the width down, rather than design extra support.
For this project, it worked out that three pallet boards made for a shelf about 11 inches wide. Perfect!
Step 3: Cut the Wood
Since my boards were not long enough for the entire length of the sill, I used six boards for the shelf top and cut them 28.5 inches long (half the total required shelf length of 57 inches) on a table saw (Figure 4). Any saw will work.
Another board was ripped in half to create support boards about two inches wide. The support boards (five total) were then cut to a length of about 13 inches.
So, a total of seven pieces of salvaged pallet wood were used to construct the shelf.
Exactly how these boards are used and what they look like is made clear in the next step.
Step 4: Dry Assemble the Shelf
Place the support boards (underboards), five in this case, on a table and then arrange the shelf boards on top of them. The easiest thing to to do is place a support board at each end and then one in the middle. The middle one supports the joint where the two sets of half sill-length board meet in the middle. Then slide in the remaining support boards in the middle of each half (Figure 5).
The front top board should be flush with the front edges of the underboards and there should be an inch or so of each underboard protruding from beneath the top boards at the back.
Once you like the arrangement you are ready to fasten them all together.
Step 5: Screw the Shelf Parts Together
This configuration required 30 countersunk wood screws about a 5/8 inches long. The wood was fairly soft so no countersinking was needed to drive them flush using a cordless screwdriver, but I did drill pilot holes slightly smaller than the diameter of the screws to avoid splitting. If your wood is hard, you may want to pre-drill and countersink the top boards for the best appearance and to prevent splitting.
Start at one end making sure the edges of the top boards are aligned with the side and front edges of the end underboard. Pilot drill each board (6 holes in this instance) and then drive in two wood screws to attach each top board to the underboard (6 screws total). Repeat the procedure on the opposite end.
Note: If you don't have a butt joint in the middle, you can just repeat the above procedure for the middle of the shelf as well.
Now work on the middle. Check the butted alignment of the two sets of top boards and center the underboard beneath them so that it supports the top boards evenly on each side. Drill and screw the top boards to the center underboard (Figure 6).
Use a tape measure to center each of the remaining two underboards halfway between each end and the center underboard. Drive in the final screws (12 in this case). Assembly is finished.
Step 6: Install the Shelf on the Sill
Set the assembled shelf in the sill so that the protruding ends of the underboards are as close to the window as possible. For this part of the job, I used 1-inch long drywall screws. Wood screws would also work.
Drive two screws in each underboard to fasten the shelf unit to the sill. That's it (Figure 7).
A shelf such as this constructed from pallet top wood is quite light yet strong (Figure 8). If you ever need to remove it, simply remove the mounting screws, fill the screw holes, and repaint the sill. No one will ever know it was there.
Step 7: Load the Shelf With Plants
We are using the shelf for some aloes and African violets. These plants and their pots are not that heavy and there is no risk of the shelf failing. So long as you don't overload it, your shelf should be plenty sturdy enough to hold even medium sized plants in clay pots (Figure 9). Enjoy your new plant shelf and take care of your plants!