Commercial-scale compost barns are typically much larger than you might need for a small backyard operation. If you have just one horse or cow, it can generate a lot of manure: up to 50 pounds every day, or 8 tons per year, according to the Pierce County, Washington website. Storing manure for future use can present challenges: it's too much for a standard compost pile, and you must compost the source material to use as a plant nutrient. A small compost barn could be the answer to the mountain of manure your horse or cow produces.
Locate your compost barn in a level area that is large enough to accommodate a structure of 8 feet wide by 16 feet long, or a bit larger. Clear the area of all plants, rocks and other obstacles. Also, locate your barn near your horse or cow's living area to make the transfer of manure easier.
Purchase or gather your building materials: you'll be constructing two side-by-side 8-foot by 8-foot stalls with open fronts and a roof covering them. You can use purchased lumber, wooden pallets or logs from fallen trees. For the roof, use metal sheeting, simple tarps or heavy-gauge plastic.
Build your foundation by leveling the ground where your barn will stand and then digging 8 to 12 inch deep holes at each corner with your post hole digger. Sink 8 foot long 4-by-4 boards as corner posts into the holes and then secure them with quick-set concrete.
Build up the sides and back of your barn by nailing boards, pallets or logs to your corner posts after the cement has set. If possible, leave ½ inch gaps between boards or logs to allow for air circulation into the manure that will be composting inside your barn. Leave the front edge of each bin open for easy access.
Construct a simple roof over the entire structure by draping plastic or tarp over the top and securing it with nails, rope or another material that will keep it in place. If you want a long-lasting roof, use metal sheeting or standard roofing materials.
To make manure compost, add manure to one of your bins every time you clean your animal's living quarters. You can also add garden and kitchen waste to your composting manure if you wish. When the pile reaches about 5 feet high, stop adding materials to the first bin and begin to build up a second pile in the vacant bin.