Dry stone causeways
Practical Action
It is also important that each of the two main groups, namely the stone gatherers and the
builders, have a 'headman', so that everybody knows what to do and works efficiently.
If possible, the site of the causeway should be on a rocky part of the bed of the river or
watercourse. It is probable that the site cannot be 'chosen', for there will already be a track
leading to it, and this will be where people need to cross. There may also be an alternative
route close by, even if there is a main track already in existence. If the existing site is across
an earthy part of the riverbed, and if there is a rocky area close by that can be used without
too much difficulty, then choose this second option. The reason for this is that you will not
need to take extra precautions against erosion when building on a natural rock foundation.
Collecting stone
You will need a good deal of stone, between 150 and 200 tonnes for the average causeway.
This needs to be of three basic sizes. First, the sides of the causeway are built with large
boulders. The heavier these are the better, and the smallest should be very difficult for a
strong man to lift. Secondly, the centre of the causeway - everything except the sides - is
filled with stone of all types, but which are reasonably easy to lift and carry. These stones will
range from the size of a football to the size of an orange, and can be of any shape. Finally,
small stones - fist-sized and smaller -are used to level off each of the three layers in the
structure.
Everyone who is helping should be organised into groups to collect the stones. If the stones
are very close by, they can be carried to the site, otherwise they can be gathered into heaps
beside a track where they can be loaded onto transport. A supply of large, heavy boulders is
needed first, as these will be laid before anything else.
Marking out the site
The standard width of the causeway is seven metres, or seven large paces. This may seem
large, but much stone will have to be used, making the structure massive and resistant to
damage during flooding. It also enables all vehicles to cross safely, including lorries and
buses.
Having chosen the site, check exactly where the lines of the causeway are to be. This should
be fairly obvious if it has been used as the crossing point for a path or track already.
The first strings need to be some 30cm off the riverbed, and level. Drive in a peg at each end
and attach the string (see Figure 2).
The lowest part of
the riverbed - which
is where the drain
will be placed -will
probably be about
half way along the
string, as in the
diagram. Use the
spirit level to ensure
that the string is
horizontal. If you do
not have a spirit
level, then use a
section of hosepipe Figure 2: Setting up the strings
to check it. This is
done with two people, who hold the hosepipe in the approximate position the pegs will be in.
Fill the hose with water. Water always finds its own level, so one or both ends can be moved
up or down until the water just comes to the top of each end of the pipe. This procedure is
easier if something like a clear plastic funnel is pushed into each end; you can then see the
water more easily.
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