To make a rammed earth block it is quite simple. Firstly you need to make some “shuttering” or “formwork”. This is a simple box with no bottom or top. Just 4 edges.
I used old scrap chipboard from a disposed kitchen, but soon found that the shipboard splits under pressure! I would strongly advise the best quality wood you can find for this stage of construction. Because mine broke I bound it with string and tape, and it just about held out long enough to make all the blocks I required.
Next: fill the frame at about an inch at a time. Don’t go filling it right up, ram it down, and wonder why all the soil falls apart when you lift it off! Small and slow is the secret to making hand made bricks. After each inch use the ramming rod, bash it down (good anger relief!) and even stand on it – you need to squash the mud together so hard that it sticks!
It is important to point out at this stage that the earth must be moist, but not soaked, and definitely NOT dry. Dry bricks don’t bond at all (I know – I wasted half an hour making one). Wet bricks wont compress as the water has no where to go.
So, you have a frame, and you are going to fill it up? Place the frame on a base board; throw in an inch of soil – and ram ram ram! Doesn’t it feel good bashing it down! Ha ha…
Once the block is full comes the tricky bit, and I find it is useful to have an extra set of hands. One person pushes down on the block, the other pulls up on the frame, ease it a bit at a time, from all sides, or you will end up breaking the brick. Ideally you would have a frame that came apart, but this is a time consuming thing to build, and seeing as we won’t make many blocks I did not bother.
When you have managed to pry the frame off of the block (hopefully with finger nails intact!) you should be left with a rather heavy, compact pile of square mud! Now, make another 9!
Leave them for a day or a week on a board, to dry out. Try not to let them get wet, and try to let them “bake” in the sun. If you are too impatient to wait use them immediately in your construction!
Once you have a collection of blocks you can begin to position them around the base that you made. Try and overlap joints as if it were a real brick wall. Where there are odd triangular gaps, and spaces between the edge of the hole and your earth blocks this can be filled with excess soil – and rammed “in-situ”
Hopefully your oven is taking shape now, and you can get a good idea of its size, shape, and final form? It is important that when you pack up for the day you COVER the oven / pit. The last thing you want is extensive rain damage destroying your work before you have the roof on! I used some plastic sheeting from an old estate agent advertising board.
In my next Blog – how to build the dome framework and construct the walls using an earth/straw mix!
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