Why Cedar?
Cedar is the standard material for outdoor compost bins because of one property: natural rot resistance. Western red cedar contains thujaplicins — natural preservative compounds that resist the organisms that break down wood. A properly built cedar bin lasts 15–25 years outdoors without paint, stain, or chemical treatment. Pressure-treated lumber raises questions about copper leaching into compost used on food crops — an unnecessary risk when cedar works as well or better.
The Case for Buying
The Greenes Fence 4-piece Expandable Cedar Composter ($89–129) is the most widely purchased model. It assembles in under 20 minutes, uses tongue-and-groove cedar boards, and can expand to 4 or 8 cubic feet. For moderate kitchen and garden waste, it is adequate and practical.
The Case for Building
Building produces a result that typically outperforms purchased bins in capacity and durability. The standard home-build is a three-bin system: one actively composting, one curing, one staging fresh materials.
Materials for a three-bin system (each bin 3x3x3 feet):
- Cedar 1x6 fence boards, approximately 120 linear feet: $80–130
- 4x4 cedar posts, 4 feet long (9 total): $60–90
- Galvanized hardware cloth, 1/2-inch mesh (optional): $25–40
- Galvanized exterior screws: $15
- Total: $180–275
Three purchased cedar bins at $90–130 each costs $270–390. DIY is comparable in cost but produces a more integrated system. Labor: 4–6 hours. Make the front boards removable — slide them into grooves cut in the uprights. Removable fronts are what separate a functional bin from a frustrating one.
Sizing and Internal Links
The minimum for hot composting is 3 cubic feet (3x3x3 feet). Smaller bins produce compost slowly as passive cold composting. For a household with a vegetable garden, a 3-bin system at 3x3x3 feet each is the cooperative extension standard. Building a cedar compost system pairs well with broader DIY garden projects. For what goes into the bin, the soil amendments guide covers nitrogen-to-carbon ratios, moisture management, and troubleshooting.
Frequently Asked Questions
- How long does a cedar compost bin last?
- 15–25 years. Posts in direct soil contact degrade faster — plan 10–15 years at the soil line. Set posts on gravel or concrete pads for maximum longevity.
- Can I use cedar fence boards?
- Yes. Cedar 1x6 fence boards ($2–4 each) are the most cost-effective option for bin walls. Use 4x4 posts for structural uprights to add rigidity.
- Is pressure-treated lumber safe?
- Modern PT lumber uses copper azole rather than arsenic-based CCA. The risk of copper leaching is debated. Cedar is the conservative, no-compromise choice for edible garden composting.
- Does a compost bin need a lid?
- Optional but useful in high-rainfall areas (over 50 inches annually). Open-top designs are easier to fill and allow rain to naturally manage moisture. In drier climates, open works well.
- What size do I need for a family of four?
- Two or three 3x3x3-foot bins enable proper active rotation. The USDA recommends a minimum pile of 3x3x3 feet to achieve temperatures that kill weed seeds and pathogens.