Compost It!

This two-bin composting system can be built by one person in about five hours. The bin holds one ton of properly moistened yard waste. It's rodent proof and has removable front doors to reduce the work of turning the compost. You'll never have to buy organic matter for your garden again!

You can also adapt this design to a three-bin system by adding another middle partition and increasing the length of the system to three feet.

CLICK HERE to download a printable version of the plan.

Design Considerations

Most of the lumber dimensions are multiples of approximately three feet, making maximum use of 12-foot-long boards.

Because this unit will be outside and is designed for the decomposition of organic matter, all fasteners and hinges must be galvanized and all lumber must be rated for outdoor use. This will provide your project with long-lasting lumber.

Construction

Step 1: The Frame

Cut three pieces of 2-inch x 4-inch x 69-inch for joists. Cut two pieces of 2-inch x 4-inch x 33-inch for headers. Mark centers of headers. That is where you will nail the center joist. Butt end nail headers to the three joists, overlapping the joists at the ends. When this step is complete, you should have a 6-foot by 33-inch rectangle with a joist down the center.

 

Step 2: The Posts

Cut three pieces of 2-inch x 4-inch x 34-inch for rear posts. Cut three pieces of 5/4-inch x 6-inch x 34-inch for front posts. Using a circular saw, cut a 3/4-inch-deep notch 1-1/2 inches from one end of each 2-inch x 4-inch piece. Chisel out the waste to create a 1-1/2-inch x 3/4-inch notch on one end of each rear post.

 

Step 3: Post Installation

Clamp the two outer rear posts to the rear corners of the frame. The bottom ends should be flush with the bottom. The notch should be up and facing inward. Using a framing square, make sure the posts are all perpendicular to the frame. Using two 3-1/2-inch x 1/4-inch carriage bolts, nuts and washers, fasten each 2-inch x 4-inch piece to the base.

 

Do the same to the two outer front posts, assembling them to the two front corners of the frame. (There are no notches on these posts).

 

To install middle front and middle rear posts, mark the center of the front and rear joists and the centers of the two remaining posts. Using two 3-1/2-inch x 1/4-inch carriage bolts, nuts and washers, fasten the front middle post to the center of the front joist, perpendicular to the base. Repeat for middle rear post.

Step 4: The Floor

Cut twelve pieces of 2-inch x 6-inch x 34-1/2-inch for floorboards. Cut a 3-1/2-inch x 1-1/2-inch notch in one corner of one floorboard. Starting on the left side with the notched board fitted around the left rear post, line up your floorboards widthwise across the base and flush with the front of the frame. (The boards will overhang the back of the frame). Leave 1/8-inch between boards. Notch the center floorboard to fit around the center rear post. Since a 2-inch x 6-inch is actually 5-1/2-inches wide, you will have a 3-5/8-inch gap after lining up the floorboards. Cut one piece of 2-inch x 4-inch x 33-inch. Lay this floorboard along the right side between the front and rear posts. Using 8d galvanized nails, secure floorboards to frame.

Step 5: The Back

 

Cut five pieces of 5/4-inch x 6-inch x 6-foot wood for back slats. Starting at the bottom and spacing them 1/4-inch apart, secure back slats to rear posts with 2-1/2-inch galvanized #8 deck screws. The ends of the slats should be flush with the sides of the rear posts.
 

Step 6: Front Door Side Runners

Cut three pieces of 2-inch x 2-inch x 29-1/2-inch. Cut three pieces of 2-inch x 4-inch x 27-1/4-inch. For side runners, stand each 2-inch x 2-inch upright behind each (5/4-inch x 6-inch x 34-inch) front post, flush with outer edge. Stand each 2-inch x 4-inch behind a 2-inch x 2-inch, again flush with the outer edge of the front post.

 

This forms a sandwich with a track in the middle (see illustration). Repeat for other side. Clamp them together and drill two 1/4-inch holes through all three boards, 6-inches from the top and 10-inches from the bottom. Join the three boards with 4-1/2-inch x 1/4-inch carriage bolts, nuts and flat washers.

Step 7: Front Door Middle Runners

Mark centers of 5/4-inch x 6-inch middle post, 2-inch x 2-inch and 2-inch x 4-inch. Clamp the three boards together at the centers to form left and right center channels. Drill 1/4-inch holes through the three boards 6 inches from the top and bottom of the middle post assembly. Join them with two 4-1/2-inch x 1/4-inch carriage bolts, nuts and flat washers.
 

Step 8: Runner Top Rails

Cut three pieces of 2-inch x 4-inch x 32-inch for top rails of runner assemblies. Set a top rail into the notch at the top of each rear post and across to the top of each inner front post (2-inch x 4-inch). Using four #8 2-1/2-inch deck screws, join each of the top rails to the tops of the front and rear posts.
 

Step 9: Front Door Slats

Cut ten pieces of 5/4-inch x 6-inch x 33-1/4-inch. Screw two #6 1-1/4-inch deck screws into the bottom edge of each of the ten boards (one on each side), leaving about 1/4 inch of each screw protruding. Check that the slat's slide easily in the runners. If they do not, your posts are not 100-percent perpendicular to your joists. You should still be able to push your posts slightly to adjust them. Using a framing square, make sure the posts are perpendicular to the frame. Using 16d nails, nail them to the floorboards.
 

Step 10: Hardware Cloth Partitions

To complete the middle partition, cut one piece of 2-inch x 4-inch x 30-inch for the middle bottom rail. Nail it to the central floorboard with 8d nails, between the front and rear middle posts. Cut one 31-inch x 34-inch piece of 1/4-inch hardware cloth. Using 3/4-inch galvanized fencing staples every four inches, secure hardware cloth to one side of the middle frame.

 

Cut two pieces of 36-inch x 33-inch x 1/4-inch hardware cloth. Fold one inch in from each edge to eliminate jagged edges. Using 3/4-inch galvanized fencing staples every four inches, secure hardware cloth to the right and left sides of the compost system.
 

Step 11: Rear Rail

Cut one piece of 2-inch x 4-inch x 6-foot for top rear rail. Fasten to the top of the rear posts, using 16d nails.

 

Step 12: Lids

Cut four pieces of 2-inch x 2-inch x 32-inch for lid sides. Cut six pieces of 2-inch x 2-inch x 31-3/4-inch for lid cross-members. Mark the centers of the four lid sides. Using 2-1/2-inch deck screws, fasten two lid sides to two lid cross-members to form a square (see illustration). Secure third cross-member to the centers of the two lid sides to reinforce the lids. Further reinforce the lids by adding 2-inch x 5/8-inch corner irons to insides of each of the corners see illustration below). Cut two pieces of 36-inch x 33-inch x 1/4-inch hardware cloth. Fold one inch in from each edge to eliminate jagged edges. Using fencing staples, secure hardware cloth to the tops of lids.
 

Step 13: Attaching Lids

Secure the lids to the top rear rail, using two 3-1/2-inch tee hinges per lid. Using fencing staples, secure one 30-inch piece of #12 jack chain to the inside edge of each lid and to the inside of each side rail at about the middle of the rail. Complete the lids by fastening a 5-inch turning hasp to the middle of each lid and the top front door slat (see assembly illustration - Steps 11 & 12).

Simple Compost

Alternate six inches of dry plant material with six inches of wet plant material.

Cover it with a thin layer of manure and a thin layer of soil or mature compost.

Place your compostable household garbage anywhere in the pile, as long as it is under the cover of the soil so that it will not smell or attract flies.

Water the pile regularly to keep it at the consistency of a squeezed-out sponge.

What Goes Into the Heap

Nearly everything that was once alive is a candidate for the compost heap. That includes old newspapers, coffee grounds, tea bags, pet hair, leaves, eggshells, spoiled fruit and vegetables, leaves, sawdust, cold fireplace ash, wool and cow and horse manure.

Do not use meat scraps, kitchen grease or materials that have been heavily treated with chemicals. Large pieces of wood, leaves and pine needles should be chopped up before composting.

A compost heap requires a ratio of about 30 parts carbon to one part nitrogen. If you have too much carbon, the pile will take forever to decompose. Too much nitrogen will make it smell. Some materials that are very high in carbon are sawdust and leaves. Materials that have heavy nitrogen content are fertilizers and blood meal.

The more diverse your pile, the more beneficial microorganisms you will attract and the faster your material will decompose.

Start building your pile in one of the two bins. Because organic material shrinks to less than five percent of its original volume during decomposition, you will be adding layers to your pile over several weeks.

When your first bin has settled and can hold no more compost, it's time to turn it over in order to speed decomposition. Remove the front door slats from both bins. Starting from the top and sides, shovel your compost from the first bin into the second, adding slats to the second bin as it fills.

Start a second compost pile in the empty bin. When it is full, it's usually time to use the compost from the other bin.

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