Building a Compost Bin: A Simple Weekend Project

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Every allotment needs a compost bin. Every garden needs one too, for that matter. It’s basically a recycling centre for your garden waste, turning what would otherwise go in the green bin into beautiful, rich, dark compost that your plants absolutely love. It’s free fertiliser. FREE. And if there’s one thing I love more than gardening, it’s free stuff. Compost ticks both boxes.

Now I covered the whole composting process in an earlier post, so I’m not going to go over all of that again. This one’s about building the actual bin. The physical structure. Because while you can technically just have a heap on the ground (and plenty of people do), a proper bin keeps things tidier, composts faster because it retains heat better, and stops the whole thing from spreading across your allotment like some sort of slowly decomposing blob. Which mine did, for a while, before I got my act together.

My first compost “bin” was a pile behind the shed. Just a pile. No sides, no nothing. It sort of worked — things did eventually decompose — but it took ages, it looked terrible, and it kept collapsing outward until it was basically a thin layer of rotting vegetation spread across a massive area. JB called it “the crime scene.” Not entirely unfair. So I built a proper bin. And it was a revelation. The compost was ready in half the time, it was better quality, and the allotment immediately looked about 500% more organised.

Pallet Compost Bin — The Classic

The most popular DIY compost bin on allotments worldwide is the pallet bin. It’s cheap (usually free if you can find pallets), easy to build, and works brilliantly. Here’s how to make one.

You need four pallets. Standard size, roughly a metre square. You can usually get them for free from industrial estates, builders’ merchants, or by asking on your local Facebook group. Loads of businesses are desperate to get rid of pallets. Just make sure they’re heat-treated (marked HT) rather than chemically treated (marked MB) — you don’t want chemicals leaching into your compost.

Stand three pallets up to form a U-shape — back and two sides. Wire them together at the corners with galvanised wire or cable ties. I used thick wire twisted through the slats, which is dead sturdy. The fourth pallet becomes the front door — wire it to one side panel along one edge so it opens like a gate. This way you can get in to turn the compost and shovel out the finished stuff.

That’s it. Seriously. Four pallets, some wire, and about twenty minutes of your time. Done. You’ve got a compost bin that holds a decent volume, has gaps in the sides for air circulation (crucial for composting), and can be easily disassembled if you ever need to move it. Cost: nothing. Value: priceless. Well, not priceless exactly, but it’ll save you buying compost for years.

If you want to get fancy, you can line the inside with cardboard or landscape fabric to stop the compost falling out through the gaps between the pallet slats. I line mine with cardboard — it eventually decomposes and becomes part of the compost itself. The ultimate in recycling.

The Timber Bin — A Step Up

If you’ve got some basic woodworking skills and want something a bit more polished, a timber compost bin is a nice weekend project. Not difficult, just requires a saw, a drill, and some patience. And probably a couple of cups of tea.

You need four corner posts (about 75x75mm, treated timber), enough planks or boards to make the sides, and some screws. Set the four corner posts in the ground — about 30cm deep for stability. Then screw planks horizontally between them to form the sides. Leave small gaps between planks for air circulation — about 1cm is ideal.

For the front, instead of screwing the planks in permanently, create a slot system — nail vertical battens to the inside of the front corner posts to create channels, and then slide the front planks down into these channels. This way you can remove front planks from the bottom to access the finished compost at the base, while the top planks hold back the newer stuff that’s still decomposing. Clever, eh? Can’t take credit for the idea — saw it on Audrey’s plot and immediately copied it. She’s ahead of us all on most things.

Wire Mesh Bin — Quick and Easy

If pallets and timber aren’t your thing, a wire mesh bin is even simpler. Get a length of galvanised wire mesh (chicken wire works but the heavier welded mesh is sturdier), bend it into a circle, and secure the ends together with wire. Stick it on bare soil. Job done.

The advantage of mesh bins is great air circulation — compost needs air to decompose properly, and mesh provides it in abundance. The disadvantage is it doesn’t retain heat as well as solid-sided bins, so composting is a bit slower. I use a mesh bin for my leaf mould (different from regular compost — it’s just leaves decomposing slowly on their own). Works perfectly for that because leaf mould doesn’t need heat, just time and air.

Bought Bins — Are They Worth It?

You can obviously buy compost bins. Councils sometimes sell them subsidised — the big black “dalek” bins you see everywhere. They’re fine. They work. They’re a bit small for an allotment but fine for a garden. The tumbler bins — the ones on a frame that you spin — are faster at producing compost but they’re expensive and they hold less volume. I’ve tried a tumbler and honestly, it wasn’t worth the money for me. The pallet bin does a better job for free.

Green Johanna and similar bokashi-style composters are another option if you want to compost food waste including cooked food and meat, which you can’t do in a regular bin. They’re more specialised and I won’t get into them here, but they’re worth looking into if you generate a lot of kitchen waste.

Sizing and Placement

Bigger is generally better for compost bins. A minimum of about one metre cubed is ideal — this is the critical mass needed to generate proper heat in the centre of the heap, which speeds up decomposition and kills weed seeds and pathogens. Smaller bins can work but they’ll be slower and won’t get as hot.

Place your bin somewhere convenient — close enough to the beds that you’ll actually use it, but not so close that it’s in the way. A semi-shaded spot is fine — full sun can dry the heap out too fast, full shade slows things down. Near a water source is handy because compost needs to be kept moist (not wet, moist — like a wrung-out sponge).

I’ve got my two pallet bins side by side at the back of the allotment, near the shed. Close to the path so I can wheelbarrow stuff in and out easily. They’ve been in the same spot for four years and the soil underneath is absolutely incredible — rich, dark, worm-filled. I keep meaning to move the bins and plant something in that spot because the soil is so good. But then I’d have to build new bins somewhere else and that sounds like effort. So they’re staying put.

Making It Work

The bin is just the container. What goes IN it matters just as much. The golden rule of composting is the green-brown balance. Greens (nitrogen-rich materials — grass clippings, kitchen scraps, fresh plant waste) and browns (carbon-rich materials — cardboard, dried leaves, straw, wood chips). Aim for roughly equal amounts of each, layered up. Too much green and it goes slimy and stinky. Too much brown and it takes forever to break down.

Turn it every few weeks with a fork to introduce air. Keep it moist. In about three to six months you’ll have gorgeous, dark, crumbly compost that your plants will thank you for. The smell of good compost — earthy, rich, slightly sweet — is one of the best smells in gardening. Better than any air freshener. Though maybe don’t quote me on that.

Look after yourselves. Take good care. 🌱