How to build a new zealand box compost bin

The quickcrop vegetable gardenHello and welcome back to the Quickcrop garden. Well, it’s a beautiful day in mid September and today we are going to build one of our large New Zealand Box composters. This the area where my old compost bins were located, I’ve emptied them now and added the compost to the garden to give me space to build my brand new bins. I’ll explain more on how this 3 box system works when we have it built but first lets look at why I’m composting in the first place, come over into the garden and we’ll take a look.

Pea plants ready to be compostedAs I said it’s mid September now so many of the plants in the garden are coming to the end of their life cycle. These pea plants won’t be producing any more pods this year so once I harvest the last ones I need to clear out the dying plants.

The plant has used nutrients from the soil to grow this foliage and produce the peas. I’ve eaten some of those nutrients when I gobbled up the peas but the rest remain in the plant. I now want to recycle the goodness left in the plant by composting this material to produce a rich dark mulch which I can add to my vegetable beds as a natural plant feed and soil improver.

Here’s some of tExcellent quality garden composthe compost I’ve added from last years garden waste, you can see it’s a lovely dark colour, it smells fresh and sweet and has a lovely crumbly consistency. I have cleaned out any bits of woody stems which didn’t break down but you can still see a few egg shells and bits and pieces from the kitchen waste we added over the year. Any material that didn’t break down can be added back to the compost bin for another cycle.

You can build these bins to any size you like but because of the size of my garden I’m going to build a big one. I’m going to make this one 4 foot by 12 foot divided into 3 separate bays. OK, let’s measure out our rectangle using a little geometry.

Creating a right a right angle compost binThe first thing we need to do is find the right angle. Now, here’s a quick and easy way of doing it. Put in your first post with the second post exactly 3 feet away. This will make up the gable of your composter so make sure it it where you want it, all your other measurements will be taken from this point.

Next I run a line at an approximate right angle to the second peg and with a pen mark exactly 4 feet on my string. Now with a tape measure I make the distance between the first peg and the 4 ft mark exactly 5 ft and then I mark this point with a peg. Now I know this angle here is a perfect right angle.

Measuring out for composterWe can now measure out our full rectangle by marking a new line at the length we want (in this case 3.6m) and running it from our right angled corner to the corner on the opposite. By keeping the line taut and just touching our 4ft marking peg we ensure this new line remains at right angles to our gable. Once you have plotted one width and length it is a relatively simple process to mark the other two by simply measuring and marking the distance from the opposite corners.

Posts for making wooden composterNext we’ll look at sinking our supporting posts. I have 8 posts in total, 4 of them plain and 4 with this groove cut in them. The plain posts go on the ends with the grooved ones placed in the middle with the grooves facing each other. It is important to have the grooved posts facing each other as this is where our dividing wall slots in later in the build.

These posts are 6 ft high and I want to build a 4ft high composter so I’m placing 2ft in the ground. My site is a little sloped here so I’m going to put the set the first post with the 2 ft mark at ground level.

Sinking posts for new zealand box compost binThe trick to getting a solid post without using concrete is to add the fill in small amounts tamping down hard as you go, I’m using an old shovel handle. Add the soil you removed from the hole a couple of inches at a time packing it down hard after every fill. Use a spirit level to make sure your post stays vertical as you go.

The finished composter will look great if all the posts are perfectly level and to do this we make a mark at 3 and half feet from the top of the corner posts and temporarily fix a board at this point. You can bring the corner posts up or down a bit in their holes until the joining board is level.

Levelling posts for a wooden compost binLeave this plank in place to easily set the two mid posts by making a mark at the same point and simply lining it up with the board. Bingo! Remember to keep checking your levels as you go as posts can move slightly while you’re working.

As I’ve said I’m making a large composter here made up of 3 separate 4 foot sections so am using a full 12 foot plank along the back of the unit. We need to leave gaps between the boards to allow air to flow through out compost bin; I’m using a wooden spacers to allow me to build the sides quickly without having to constantly check for level every time. Fix the bottom board level first and then continue up the the rest.

The middle separating boards simply slot into the grooves cut in the centre panels and can be easily added or removed.

Marking brackets for compost binThe front boards are also relatively quick to add using our unique moulded plastic bracket system. Make a mark 6 inches apart on the sides of the posts and use the template provided to mark out the position of the brackets with a pencil.

The brackets are attached with the open end facing upwards and are fixed with the screws provided. When all your brackets are in place simply slot the retaining timber slats in place.

OK, we’re done. YNew zealand box composter hero shotes it may look a little complicated at the start but that’s really just me being pedantic. So, now we have it built let me show you how it works:

The idea is you start your composting in one side of the bin, I’m adding some fresh material from the garden here, remember our old pea plants from the start of the video. The beauty of the removable slats is the you only place them at the height of your pile making the bins really easy to fill.

Quickcrop new zealand box composterOnce the first part is full it will be partially broken down and will need to be turned to allow air into the pile which helps it break down further. Fork your compost into centre bin, in doing this you are mixing and aerating the material. Your pile now spends a number of weeks in the centre section while you begin again in the first with new garden and kitchen waste. The middle section is then emptied into the last bin to complete the final stage of the composting process while you transfer the first into the middle again and so on.

Mixing compost in new timber compost binYour finished compost will be the rich, dark and crumbly material you want having been tuned and aerated twice. Any material that hasn’t completely broken down like thick cabbage stems can be added to the first bin again to go through the cycle a second time.
If you want to clear the whole unit the separating planks can be easily removed allowing you plenty of room to work.

We also recommend using a lid in wet climates to help keep heat in the pile and avoid it getting too wet. We also supply simple hinged wooden lids for this purpose.

Remember these bins can be made to any size you wish depending on how much garden waste you have. Our standard version features 90cm or 3ft bays which is plenty for a relatively large vegetable garden.

Finished quickcrop compost binThe New Zealand Composter is the best solution if you have relatively large amounts of material to process. Like any open slatted timber composter it is also much more forgiving than an enclosed plastic unit due to it’s superior aeration and will still produce the goods even if your mix of materials isn’t quite right.

More details are available on our websites and including photo instructions and any other equipment you may need for composting or any aspect of home vegetable growing. Remember we are the experts and we’re always here to help.

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