Rubble stone is the by-product of either natural geological occurrences or work in a quarry. While it is usually used as fill for mortared walls, it may also be used on its own to create beautiful, rustic rubble stone walls that will enhance any landscape. It is also an economical resource, and building with it is almost like solving a puzzle as you work to fit the pieces together.
Lay out a rough outline in string of the size and shape of the rubble stone walls you want to build. Determine the height, length and width of each.
Calculate the amount of rubble stone needed for each wall by multiplying the three measurements to get the total volume. One cubic metre of wall requires approximately 2.4 tonnes of stone. Add extra to ensure you have enough and to account for the irregular shape of rubble stone and the varying density of the rocks.
Collect or purchase the required amount of rubble stones. Shale, slate, schist and limestone are good choices for building rubble stone walls as they are easily split if necessary.
Sort the stones into piles of similar sizes and shapes to make the process of fitting the rubble stones together easier and quicker.
Building the wall
Dig a trench the length of the wall. It should be at least 30 cm (1 foot) wide for a rubble stone wall up to 90 cm (3 feet) high, wider if the rubble stones are wide, and at least 15 cm (6 inches) deep.
Stack the largest rubble stones in the trench to form the wall's footing. This will help prevent the wall from sliding forward. Make sure the stones are level and complete the whole length of the wall before continuing.
Use a tamper to pack the rubble stones in place, adding dirt as needed. Fill in space between the larger rocks with smaller rocks, using the hammer and chisel to break them up if necessary.
Place the second layer of rubble stones so that they fill any openings created by the first layer. Add dirt and smaller rocks to fill in the spaces. Water carefully poured on the fill will help it settle. Try to maintain the rule of two stones over one, one stone over two for maximum strength and stability. Build each layer in this manner until the desired height is reached.
Split some of the larger rubble stones that are left so that they are flat and place on the very top of the wall to give it a more finished appearance.
Build the levels at an 8 degree slant and fill behind with dirt to allow gravity to help hold them in place. Always wear safety goggles when breaking rocks. Work gloves should also be worn, especially if you are not experienced with a chisel.