We live in a relatively urban area in an apartment with zero land that we can compost traditionally on. As voracious plant-eaters we have quite a lot of vegetable scraps that we morally can't send to the landfill. The solution is a worm bin that resembles furniture, won't stink up the place if properly managed, and can process the waste of at least two plant-chomping people.
These instructions will show how to construct a three-tiered, wooden worm bin out of readily available materials. In the future we will cover how to add and care for the wormies.
How does it work?
The three-tiered system works like a magic food to compost machine. The three boxes are identical and interchangeable. You put food scraps and woody material (paper, wood shavings, etc.) into the top layer which worms eat over time, filling the top box. Once the top layer is nearly full, you put the empty bottom layer on top. Then once that layer is nearly full you put the last empty box on top. By the time that one is full you will have premium, beautiful soil in the bottom layer that can be emptied out and used. The cycle keeps going. The layers are important because the worms will seek refuge, rest, and reproduce toward the bottom.
Since the layers are identical, the directions will show how to make one box, the base, and the lid.
The worm bin is ventilated and will ONLY smell bad if it is poorly managed. It should smell like the floor of an old growth forest. More on how to achieve that to come.
Step 1: Materials, Tools, and Dimensions
All materials can be purchased at your local Home Depot if not reclaimed from somewhere else. This particular worm bin was made for about $40. However, it is make out of pine which will not last as long as more expensive woods like oak. But I would rather have a pine worm bin than no worm bin at all.
20" wide x 15" deep x 24" tall (Can adapt to 15" x 15" if you don't make that much food waste)
Three sets - 8" x 1" board cut into two 13.5" and two 20" sections (first image).
Three sets - 1" x 0.25" trim cut into two 15" sections and two 20.5" sections (second image).
Two boards - 1/2" thick cardboard cut to 20" x 15 (third image)
Two sets - 5/8" wide cove trim cut at 45 degree angles. Two 16.25" and two 21.25" (fourth image)
0.25" aluminum wire mesh cut to three 15" x 20" squares (roll in image)
24, 1.75" wood screws
5/8" long brads (those little finishing nails)
1/2" long staples
One garbage bag to cover the inside of the base to prevent leaking.
The tools in the picture are just a few of the tools that were used. The japanese pull saw is the best available hand saw in the world and that one cost $30 online.
Jig Saw or coping saw (Just for cutting handles)
Staple gun with staples and brads (Can be done with a hammer)
Step 2: Building Boxes
There are three identical boxes in the worm bin. Take your 1" x 8" boards and butt the 20" boards against the end of the 13.5" boards. This is clear in the bottom left image. I took the time to drill pilot holes to prevent splitting and to ensure that the corners were flush. Then just screw in your 1.75" wood screws.
If you care hide the screw heads, you can drill a 1/4" deep hole with a 3/8" diameter drill bit. Then you can glue screw caps or cut dowels to cover the hole.
If you haven't already, cut the trim to two 15" strips and two 20.5" strips. Overlap the trim over the top of the boxes by 1/8". This will create a lip so the boxes can sit on each other. 4 or 5 brads on each piece of trim will do the trick. It's optional, but adding some wood glue under the trim will make it a lot stronger.
Tip: Stack the boxes before you nail on the trim to ensure that the boxes can fit.
Step 3: Cut Handles
The pattern can easily be customized. I made a handle pattern that was 4" wide and 1.25" tall.
In order to center this pattern, you need 5 1/2" inches to the edge of the side. I set it 2 3/4" from the top as well. I wrote this on the pattern to make it simple.
Drill a guide hole, preferably on the edge of the outline. The cutting can be done with a jigsaw like in the picture or a coping saw, which looks is like a smaller hacksaw made for wood.
A pictures is worth 1,000 words, so follow the 7 picture cutting sequence for 7,000 words worth of instructions.
If you don't have any fancy saws, just drill two 1" diameter holes about two inches apart and cut or chisel out the wood in between them.
Step 4: Grating
Using scrap mesh that you hopefully have after cutting out your 20" x 15" sheets, cut a total of 12 rectangles at 2" x 5". On the inside of the handles double up the mesh so worms won't go AWOL and staple them on. We lightly hammered the pointy edges into the wood to minimize worm hazards.
Lay the grate over the bottom of the box. Using the principles upholstery, first staple the middle of an edge, then the middle of an opposite edge, then go around from there. This should reduce bulging. Hammer proud staples in so the box can sit well into the boxes below it in the stack.
Step 5: Base and Lid
Grab one of your 15" x 20" plywood boards and one set of cove trim pieces. If you haven't cut them yet, you need two 16.25" and two 21.25" lengths. These measurements are to the end of the point of the 45 degree angle. Make sure that you cut the 45 the proper way using the pictures as guides.
Stretch a doubled garbage bag over the top of the base board and tack the trim on to anchor it. The bottom of the trim should be flush with the bottom of the base board. In other words, everything will be even with the ground on the bottom. There should be a slight overlap of the trim on top so the boxes can set into it like they set into each other. Tacking the trim on can be tricky so don't worry too much about getting the plastic tight. Also, there is only plastic on the base.
Grab your second 15" x 20" and your last trim pieces. The lid is different from the base because the trim will not be flush to the board. The last picture is the lid upside down which illustrates this. It shows how the trim is offset in an opposite way so it can fit into the top of the boxes. As a guide for offsetting the bottom of the trim, I just followed the line of the first ply layer.
Not only are you finished with the box now, but you can literally apply finish to it to make it nicer looking and longer lasting if you want. I would suggest any natural, VOC free finish that won't choke out the worms. I just used a very light layer of coconut oil, but don't use this if you are in a hot climate because it might go rancid.
Step 6: WORMS!
We applaud your interest in worms, DIY, and reducing waste! Let the vermicomposting begin!
Thank you for reading!
*Coming soon, instructions on how to start and care for a worm bin.