Building A Cement Block Enclosure
[Line drawing - Three Section Block Enclosure]
Perhaps the easiest home compost bin to build is one constucted of cinder blocks or concrete blocks as the primary building material. These blocks are relatively inexpensive. A serviceable bin can be erected in just a few hours, requiring few construction skills. A block bin does not need to be built with mortar. As long as they are stable, the weight of the blocks themselves are sufficient to hold in the organic materials. It is important to decide at the outset whether you want an open three sided bin or a closed four sided bin. The closed bin is fine for a simple pile while the three sided bin is probably more desirable if you intend to turn the pile from time to time.
Locate the bin on open ground, not on a paved surface, so that the pile can drain into the soil below. Also, earthworms and the other microbes that live in soil will be able to migrate into the pile and make their contribution to its decomposition. Make sure the ground where the bin is to be located is level. This will make the bin more stable and attractive.
To achieve a certain amount of precision in the construction process, use stakes and string to lay out the outside measurements of the bin. Then set the block against the string, checking to be sure the corners are square. Use a builder's level to be sure the block is sitting level on the ground and that the sides are vertical to the ground. If on the other hand, the goal is simply an enclosure that doesn't fall over, just eyeball the placement of the line of blocks and skip the measuring tools completely.
As the drawing indicates, you can build as many adjoining sections of the cement block bin as you feel you need. Also, the size of the bin described here is purely arbitrary. For a simple pile the size of the bin may simply be a function of how much block you have on hand. For a managed composting system, two or more sections makes turning the pile much easier. It can be dumped into the bin next door.
As a general practice, most cement block bins are built so there is a small space left between each block to allow for air access and water drainage. Two to four inch spaces are sufficient. Because cinder blocks typically have open holes in them, a bin with the blocks butting up against each other will also work pretty much as well as one with the air spaces. It is wise, when laying block on top of other block, to stagger the placement of the blocks by postioning each one over the air space or jointure of the blocks in the previous layer below. This gives the structure more strength. However, staggering the block from layer to layer, results in open ends and corners which can be left as is, or filled with half pieces of block. It depends on how important a finished look is to you.
As indicated in previous chapters, a pile will decompose more quickly if it is covered in some way. With cement block bins, it is a simple matter to fashion a cover of some kind (old shower curtain, tarp, etc.) to drape over the top of the pile once it is built. To improve the appearance of a block bin, plant colorful annual flowers or vines such as morning glory or honeysuckle around the outside of the bin to soften the look of the cinder blocks.
| Parts For Single Section or Triple Section Bin | ||
|---|---|---|
| SIZE | SINGLE SECT. QUANTITY | THREE SECTION QUANTITY |
| 8 x 8 x 16 inch blocks | 30 | 90 |
| 8 x 8 x 8 inch half blocks | 5 | 15 |
Note: Some blocks can be scored at midpoint so that they can be broken to become half blocks.
TOOLS FOR THE MORE PRECISE BUILDER:
Measuring tape
Large carpenter's square to square the corners
Four foot carpenter's level to level the rows of block
Hammer to break up blocks
One-inch wide cold chisel to break blocks
Eye protection for breaking up blocks
GENERAL CONSTRUCTION STEPS FOR CEMENT BLOCK BIN(S):
1. Select a cleared, level area of firm ground where the soil is permeable enough to absorb rain or seepage from aging compost. You may want to break up the soil inside where the blocks are set to make sure worms and other microbes have good access to the pile. However, the soil under the block should be as firm and tamped down as possible.
2. Lay out the outer outline of your bin (one section, two sections, etc.) by driving stakes at each of the four corners of the allotted space. Calculate the size of the bin according to the amount of avaiable block. The easiest way is to lay out some block around the outline of bin to get an idea of the size, and then place the stakes and string as guides. Determine how much space you want to leave between each individual block. Fasten the string between the stakes at least 6 inches above the ground and level with it if possible.
3. Position the first layer of blocks, making sure they are flush with the string and are indvidually and collectively level. Adjust the ground surface if necessary to assure this.
5. Lay the second course of block, remembering to stagger the blocks so the middle of each block on the second tier rests over the space between two blocks on the first tier. This leaves a space at the end and on the corners. Here is where the half blocks will be situated. The half blocks will likely need to be butted up against the full sized blocks, eliminating the air spaces in those instances which causes no problems.
6. Now lay the third course of block, again staggering them over the spaces between the block in the second tier.
7. You can make as many tiers in your bin as you wish. This bin uses 5 tiers which creates a single bin area that will hold about 25 to 30 bushels of organic material if filled to the top or a little above the top.
Cinder Block Compost Bin with Wood Front
[Line drawing - One Section Block Bin With Wooden Front]
Here is a block bin with a wooden front that allows for removable wooden slats which make it easy to access the pile to turn it. Butt the end blocks up snugly to each other at the front ends of the layers so there is a smooth front face on which to mount the wooden front panel. This bin will hold from 25 to 30 bushels of material when filled to slightly above the top.
| Parts Chart | |
|---|---|
| MATERIALS | QUANTITY |
| 8 x 8 x 16 inch cinder blocks | 39 |
| 8 x 8 x 8 corner blocks | 12 |
| 1 x 4 x 8 feet lumber | 2 pieces |
| 1 x 2 x 8 feet lumber | 1 piece |
| 1 x 6 x 10 feet lumber | 2 pieces |
| Nails or screws as fasteners | as many as needed |
Note: You can buy corner blocks or you can make them by scoring the midpoint so that they can be broken to become half blocks.
CUTTING LIST:
2 pieces 1 x 2 x 3'2"
4 pieces 1 x 4 x 3'2"
6 pieces 1 x 6 x 3'2 1/2"
TOOLS:
Measuring tape
Large carpenter's square
Four foot long carpenter's level
Hammer
One-inch wide cold chizel (for breaking blocks)
Hand or power saw
Power drill
Eye protection
CONSTRUCTION STEPS:
1. Select a cleared level area 5 feet square of firm ground where the soil is permeable enough to absorb rain or seepage from aging compost.
2. Position the back wall blocks according to line drawing, making sure they are butted snugly and are individually and collectively level, adjusting the ground surface as necessary.
3. Position the bin sides according to the line drawing with space between a full block and a half block so that the outside length of each side is that of three full blocks. Use the square and straight edge to insure the open side of the bin is the same length as the back wall.
4. Lay the second to fifth courses of cinder blocks according to the line drawing.
[Line drawing - Showing the Wooden Structure]
5. The wooden slats, making up the front panel of this bin are held in place by a wooden framework made of three pieces of lumber. In the drawing those pieces are labeled piece "W", piece "X", and piece "Y". The narrower inside piece "X", is positioned so that when the bin is finally assembled the wooden slats slide down a slot made up of the two wider pieces "W" and "Y", separated by piece "X".
6. There are any number of ways to mount this wooden frame, made up of the three pieces of lumber, on the two front ends of the block bin. One method is to use plastic or metal masonry anchors in the block and attach the first board to the blocks with screws held by the anchors. Then mount the thin board and outside board to the anchored board with screws or nails. Another, less secure, method is to use 3 inch masonry nails to secure the three pieces of lumber into the block.