While the majority of compost bins are designed to be placed directly on soil, allowing worms and other soil creatures easy access and permitting leachate to drain way, there are significant groups of composters that are mounted
off the ground or are designed to be placed on a solid base. In addition, there are systems, such as wormeries with different models available for outside and for indoor use.
In a patio garden a “conventional” compost bin should
be positioned, if practicable in a sunny part of the garden on bare soil but if this is not possible in a slabbed or courtyard garden a few slabs could be removed to create a space for the bin allowing direct access to soil. If lifting slabs or pavers is not
practicable, the bin can be located directly on concrete, tarmac, patio slabs or decking. However, it is normal for liquid (leach ate) to seep out of a compost bin and this may stain surface.
One way of avoiding this on patios, balconies
and roof gardens a small raised bed may be created to house the bin to reduce the likelihood of staining the surface. The slaps or decking within the raised bed where the bin is to be placed should be covered by at least three inches of coarse gravel or stones.
This is covered with a geotextile membrane, fabric landscape liner, degradable plastic or coir, followed by the soil layer. Once compost has been produced, it can be used to increase the level of organic matter in the raised bed soil to absorb excess moisture
so to reduce seepage. Compost worms, and other beneficial composting creatures, can be introduced by the addition of inmature compost from garden bins or fresh manure to both the bin and the raised bed. It is advisable to monitor the condition of the bin and
make further additions when required. One of the advantages of mounting the bin on a raised bed is that the compost in the bed will form a reservoir for the compost creatures.