The Q&A Archives: compost bin construction

Question: I would like to build a compost bin in my backyard. I live in Mid-Michigan and would like to know what construction materials I need to build a 3 x 3 x 3 compost bin. Can you give me any help?

Answer: I love composting, because there really is no "proper" way--no matter what you do, eventually everything will turn into compost. To speed the process along, you need four ingredients: carbon (browns), such as leaves, straw, shredded paper, woody prunings from the landscape; nitrogen (greens), such as grass clippings, kitchen fruit and veggie scraps, fresh clippings from the landscape, manure; water, and oxygen. An easy way to start out is to mix the carbons and nitrogens in about a 50/50 ratio. As you construct the pile, sprinkle it with water from your hose. The ingredients should be as wet as a damp sponge. Don't try to make the pile and then water it all down from the top. The water finds paths to pour through out the bottom! The pile should be at least 3 feet by 3 feet by 3 feet (1 cubic yard) to have enough mass to insulate and retain heat. As the microorganisms that are doing the decomposing die off, they release heat. When the pile cools, they've probably run out of oxygen, which is where turning the piles frequently comes in. The more turning and reapplying of moisture, the more quickly the materials will decompose. On the other hand, you can construct a good pile and then just let it sit. It will decompose, but take 6-8 months. Hint: the smaller the ingredients, the faster they will decompose. This is just a quick outline to get you started. For more info, a great book is "Let it Rot" by Stu Campbell and it's usually available at libraries and bookstores.

You don't really need to build a compost bin, but if you decide you want to, here's what you'll need:

STEP 1. CONSTRUCT THE REAR WALL OF THE BINS. Begin by cutting two pieces of 2x4 (1-1/2"x3-1/2") lumber each 96 inches in length. These pieces will be used to make the rear rails. Next cut three pieces of 2x4 lumber to 48 inches for the uprights. Cut one section of 48-inch wide welded wire mesh (2x4 inch mesh size) to 96 inches. Lay the two rear rails face down parallel to each other, 48 inches apart. Carefully lay the three uprights on top of the rails, keeping their ends flush to the edges. Space the uprights with with one on either end of the rail and one in the center. Mark the pieces for half-lap joints, then cut half-lap joints in the rear rail and on the ends of the uprights. Attach the rear wall uprights to the rear rails using three 1-1/2" #8 flathead wood screws per joint. Fasten the 48-inch wide meshing to the rear wall using 5/8-inch staples driven at intervals of approximately 10 inches.

STEP 2. SECURE THE REAR WALL. To prevent the compost bin from being blown away in high winds it is advisable to secure it to the ground. Move the rear wall to its intended location. Stand the wall vertically and temporarily brace it with scrap lumber. Against the outside of the wall, in line with the uprights, drive three 60-inch high fencing stakes into the ground to a depth of 12 inches, until their ends are flush with the upper edge of back wall's top rail. Use a sledgehammer if necessary. Drill 3/16-inch diameter holes through the fencing stakes into the top and bottom rails to a depth of 1". Fasten the fencing stakes to the rear wall rails using 3/8" x 1-1/12" screws.

STEP 3. BUILD THE SIDES AND FRONTS OF THE BINS. Cut 20 pieces of 2x4 stock to 48 inches each. Then cut five sections of 48-inch wide mesh fencing (the same as the rear wall) to 48 inches each. Assemble five panels, each measuring 48x48 inches. Construct each panel using lap joints, following the same procedure for building the rear wall. Next attach the mesh fencing to each panels using staples, as was described earlier. Join three of the equal sided panels to the rear wall to form bin sides. To fasten the sides, first butt an upright of each panel against the upright of the rear wall. Drill three 1/4-inch diameter pilot holes from the outside of the rear wall into each upright. Then enlarge the holes in the rear wall to 3/8-inch. Install 3/8x4-inch lag bolts fitted with washers. Adjust the bin sides so they are perpendicular to the rear wall, then drive two 60" fencing stakes into the ground to secure the bin sides as you did for the rear wall. Secure each stake in the same manner described for the rear wall.

Use the two remaining panels for the front of each bin. You can attach the panels with two hinges on either side of each bin so they will swing open or you can make them removable and attached as needed with hooks securing the doors.
Enjoy your composting!

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