Now, you need to be let in on my secret weapon… none of this would have happened if it hadn’t been for SID.
SID (Soil Improvement Device) is a contraption that I had already built prior to even hearing of rammed earth. He came about because we had a problem. We wanted to grow vegetables in the garden but found that our topsoil was contaminated with brick rubble, rope, plastic and no end of glass. We couldn’t grow in that, so SID was conceived.
SID screens the soil and ejects particles over 25mm down the top shoot and then a second lower screen of 12mm separates particles between12mm and 25mm down another lower shoot. The earth particles under 12mm go straight through SID into the wheelbarrow and are returned to the raised beds for our crops to grow in.
When I started to look into rammed earth building, I soon realised that one of the main hurdles you need to jump is soil screening. SID can process around one tonne an hour (if you have two wheelbarrows and two pairs of hands), so it didn’t take too long to sort out the 39 tonnes to build the Eco-Shed.
I already had around 26 tonnes of subsoil from the excavations from the shed’s footings and the other13 tonnes came from a building site six miles down the road. All this subsoil was processed through SID. The total cost to build him was just £45, including the power unit – a £25 drill from a large DIY chain. Keep your receipt, as they only seem to do about 13 tonnes before the inevitable happens! I am sure that many of you could improve on my design, especially the power unit. I have seen some examples based on SID that use a jigsaw to cause a vibrating effect to process the material. Even better would be a powerful motor – the kind you get on concrete mixers – with a speed controller.
All the big stuff such as brick rubble and stones, which comes down the top shoot, can be re-used as hardcore for your subfloor and the smaller stones from the lower shoot we used for pathways around the garden. Everything in the barrow is below 12mm and this is what I used for my rammed earth walls.
I have since built a new soil sieve which is a better design as it puts less strain on the motor.
Finally, don’t forget the safety goggles, have fun and good luck!