Garden Composters
A compost bay that never rots into the compost
Compost destroys the thing containing it. PolyBrick® bays are unaffected: no rot, no treatment, no replacing, and open joints that let the heap breathe.
Why PolyBrick works here
There is a particular irony in a wooden compost bin. The heap inside it is a machine for breaking down organic material, and the bin is made of organic material. Pallets last two or three years. Treated timber lasts a little longer and puts preservative in contact with compost you are going to spread on food crops.
PolyBrick is not food for the heap. It does not rot, and the material is inert, so nothing moves from the bay into the compost. It is UV stabilised, so the sunny side does not go brittle while the shaded side stays damp.
The other advantage is practical: because blocks push-fit rather than being fixed, a bay can be taken apart. Anyone who has tried to turn a heap or empty a bin through a small door will understand why that matters.
Where this works well
- Single garden compost bays
- Two and three bay rotation systems
- Leaf mould bays
- Allotment and community composting
- Grass clipping and green waste storage
- Muck heap bays and manure storage
- Wood chip and bark storage
- School and community garden projects
At a glance
| Assembly | Push-fit interlock. No tools, no mortar, no fixings |
| Access | Front courses can be removed to open the bay for turning and emptying |
| Aeration | Build with gaps between blocks so air reaches the heap through the walls |
| Base | Open to soil, so worms and organisms move in and liquid drains away |
| Contact | Inert. Nothing leaches into compost destined for growing |
| Material | 100% recycled polypropylene, UV stabilised, made in the UK |
| Service life | 25 years under warranty |
| Maintenance | None. Rinse it down if you want to; that is the extent of it |
Build it to breathe
A compost heap needs air. Without it the process goes anaerobic, which is slower, colder, and produces the sour smell that makes people give up on composting altogether.
Build the side walls with deliberate gaps between blocks rather than solid, so air moves in through the walls along the full height of the heap. It is the same principle as a slatted timber bay, without the slats rotting.
Leave the base open to the soil. Worms, fungi and bacteria colonise the heap from below, liquid drains away instead of pooling, and the heap stays in contact with the ground it came from.
Why three bays beats one
A single bin is a place to put garden waste. A three bay system is a process, and it produces considerably more usable compost with less effort.
The principle is simple: bay one is what you are filling now, bay two is what you filled last and is actively rotting, bay three is finished compost ready to use. When bay three empties, everything shifts along, and the act of moving material between bays turns and aerates it, which is what accelerates the whole process.
Because the system is modular, you can start with one bay and add the others as your volume grows, rather than committing to the full run on day one.
How it goes together
- Choose a level spot with reasonable access. You will be wheeling barrows to it in all weathers, so a route that is not across wet lawn is worth having.
- Clear the ground and level it. Leave the base as bare soil rather than paving it, so the heap stays in contact with the ground.
- Lay the first course and check it level in both directions. Everything above follows it.
- Build up the back and sides in courses, leaving gaps between blocks for airflow, and staggering the joints between courses.
- Build the front as loose, stackable courses that lift out rather than as part of the structure. This is your access.
- Where you are building multiple bays, share the dividing walls between them.
- Cap the top course if you want a finished edge, and leave the top open or cover the heap with a sheet or old carpet to keep rain off.
The removable front
This is the detail that makes a bay pleasant to use rather than a chore, and it is where most bought bins fail.
Build the front wall as courses that simply lift out. Fill the bay with the front in place, then remove the courses one at a time as you dig the heap out, so you are always working at a comfortable height with the face of the heap open to you.
Compare that with a plastic dalek bin, where finished compost is at the bottom, under everything you have added since, behind a hatch the size of a letterbox. The removable front is the single biggest reason people actually turn their heaps.
Sizing the bay
Bigger heaps work better. A heap needs enough mass to hold heat, and a small bin loses it to the outside faster than the process generates it, which is why little bins produce cold, slow compost.
Around a cubic metre is the usual working minimum for a heap that heats properly. Below that, composting still happens, it is just slower and stays cooler, which means weed seeds and roots survive it.
Do not go so wide that you cannot reach the middle with a fork. Depth front to back is more useful than width, and if you have the space, another bay beats one enormous one.
Muck heaps and green waste
The same structure works for manure storage, grass clippings and wood chip, and for those the material advantage is even clearer, because these are wetter, heavier and harder on a container than garden compost.
For muck heaps, check what applies to you on storage siting and run-off before you build. Rules on storing manure near watercourses, ditches and boreholes vary, and the position of the heap matters more than the bay it is in.
Get it right first time
The one thing worth knowing: put it somewhere you will actually walk to.
The most common composting failure is not technique, it is distance. A bay at the far end of the garden, across the lawn, behind the shed, gets used enthusiastically in spring and abandoned by October when it is dark and wet.
Site it somewhere on a route you already take, with a firm approach underfoot. Slightly less tidy and considerably more used beats beautifully hidden and full of nettles.
Ask our engineer
Questions about bay sizing, multiple bay layouts or muck heap storage? Ask below, or get in touch directly.
Common Questions
Why use plastic blocks for a compost bay instead of wood?
A compost heap is a machine for breaking down organic material, and a wooden bin is organic material. Pallets last two or three years, and treated timber puts preservative in contact with compost you may spread on food crops.
PolyBrick does not rot and is inert, so nothing moves from the bay into the compost, and it is UV stabilised so the sunny side does not go brittle.
Does a compost bay need gaps for airflow?
Yes. A heap without air goes anaerobic, which is slower, colder and produces the sour smell that makes people abandon composting.
Build the side walls with deliberate gaps between blocks so air moves in through the walls along the full height of the heap. It is the same principle as a slatted timber bay, without the slats rotting.
Should the compost bay have a base?
Leave it open to bare soil. Worms, fungi and bacteria colonise the heap from below, liquid drains away instead of pooling, and the heap stays in contact with the ground.
Paving underneath cuts the heap off from the organisms that do the work.
How big should a compost bay be?
Around a cubic metre is the usual working minimum for a heap that heats properly, because a heap needs enough mass to hold heat and small bins lose it faster than the process generates it.
Below that, composting still happens but stays cool and slow, which means weed seeds and roots survive. Do not go so wide that you cannot reach the middle with a fork.
How do you get the compost out?
Build the front wall as loose courses that lift out rather than as part of the structure. Remove them one at a time as you dig the heap out, so you are always working at a comfortable height with the face of the heap open.
It is the single biggest reason people actually turn their heaps, compared with a bin where finished compost sits at the bottom behind a small hatch.
Is a three bay system worth it?
It turns composting from storage into a process. Bay one is what you are filling, bay two is actively rotting, bay three is finished and ready to use. When bay three empties everything shifts along, and moving material between bays turns and aerates it, which accelerates everything.
Because the system is modular you can start with one bay and add others as volume grows.
Can I use it for a muck heap or grass clippings?
Yes, and the material advantage is even clearer, because manure, clippings and wood chip are wetter, heavier and harder on a container than garden compost.
For muck heaps, check what applies to you on storage siting and run-off before building, since rules on storing manure near watercourses, ditches and boreholes vary and the position matters more than the bay.
Does the bay need a lid?
Not structurally, but covering the heap helps. Keeping heavy rain off stops the heap becoming waterlogged and cold, and retains warmth.
A sheet, a board or an old carpet over the top is enough, and it can be lifted off when you add material.
Will it need any maintenance?
No. There is nothing to rot, treat, stain or replace, and no fixings to work loose. Rinse it down if you want to, but that is the extent of it.
The blocks carry a 25 year warranty and can be dismantled and reused elsewhere if you reorganise the garden.
