GuideCompost Bins
Build a Three-Bay Compost Bin from Pallets
A three-bay bin is the classic way to make a lot of compost: one bay fills with fresh material, one is working and one holds finished compost ready to use. Built from reused pallets, it costs very little and takes an afternoon.
What you will build
You will stand pallets on edge to form a back wall and four side walls, making three bays open at the front. The fronts are closed with loose boards that slide into slots, so you can open a bay to fill, turn or empty it.
Pallets come in different sizes and some were treated with chemicals, so the first step is choosing the right ones. Look for the treatment stamp: pallets marked HT (heat treated) are the ones to use. Avoid pallets marked MB (methyl bromide), unmarked pallets of unknown origin and anything stained by spills.
Real-world examples
Photos of similar builds by other people, shared under open licenses. They show the idea in practice; the details differ from this guide.
Materials
- 7 pallets of the same size, stamped HT (3 for the back, 4 for the dividers and ends)
- Exterior screws 3 in (75 mm), or galvanised brackets and shorter screws
- 4 lengths of 2 × 2 in (45 × 45 mm) timber per front, to make the board slots
- Boards about 1 × 6 in (20 × 145 mm) to slide in as front panels
- Optional: wire mesh to line the inside against rodents
- Optional: old carpet, a tarp or boards as lids
Tools
- Drill/driver
- Saw
- Tape measure
- Spirit level
- Pry bar for loose pallet boards
- Gloves and safety glasses
Step by step
1Choose and check the pallets
Collect pallets of one size with the HT stamp. Knock in or remove protruding nails, replace broken boards and avoid any that smell of chemicals or show stains. Wear gloves: pallets are full of splinters.
2Prepare a level site
Choose a level spot on bare soil, partly shaded, with easy access for a wheelbarrow. Clear weeds and level the ground roughly. Compost works best on soil, where worms and moisture can move in from below.
3Stand up the back wall
Stand three pallets on edge in a row to form the back wall and screw them to each other through their blocks or with brackets. Check that they stand straight up.
4Add the dividers and ends
Stand a pallet at right angles to the back at each end, and two more in between to make three bays. Screw each one firmly to the back wall at top and bottom. The structure becomes much stiffer once all the sides are joined.
5Make slots for the fronts
Screw two strips of 2 × 2 in timber upright to the front edge of each divider and end, leaving a gap just wider than your front boards. The boards then slide down into the slots and lift out one by one.
6Add the front boards and a lid
Cut the front boards to fit between the slots and drop them in. Add boards as each bay fills. Cover the bays with old carpet, a tarp or boards to keep heavy rain off and the heat in.
Tips for a better result
- Mix roughly equal volumes of green material (kitchen scraps, grass cuttings) and brown material (dry leaves, shredded cardboard, straw).
- Turn bay one into bay two when it is full, and bay two into bay three when it has broken down; the turning adds air and speeds things up.
- Keep the heap as damp as a wrung-out sponge.
- Chop larger material small; it breaks down much faster.
Common mistakes to avoid
- Using unmarked or chemically treated pallets.
- Building the bin far from the garden, so it never gets used.
- Adding meat, fish, dairy or cooked food, which attract rats in an open bin.
- Letting the heap get waterlogged or bone dry; both slow composting down.
Safety
- Wear gloves when handling pallets and compost, and wash your hands afterwards.
- Wear safety glasses when prying off boards or cutting old wood, which can hide nails.
- Do not put diseased plants, pet waste or perennial weed roots with seed heads into a cool home compost heap.
General guidance only. Follow the instructions for your tools and materials and your local rules, and use a qualified professional for electrical, gas and structural work.
Finishing up
A three-bay bin turns garden waste into a steady supply of compost and keeps the work tidy. When a pallet eventually rots, it is easy to unscrew it and replace it with another, so the bin can last for many years.
About this guide: written by the DIY Outdoor Builds editors from general, widely used building and gardening practice. Text and illustration © DIY Outdoor Builds. Photos are by the people credited under each one, used under their licenses. Found an error? Let us know.
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