of the support sheet illustrated in fig2 a member 16 of h cross section is affixed approximately mid centre of the channel 15 and extends away from the open section of the elongated channel 15 in use the cutter sheet if required can be gripped by any suitable means e g by the well known pile driver and driven longitudinally into the ground to cut tree roots etc the cutter sheet is then removed by any conventional means if necessary the adapter is attached to the support sheet as illustrated in fig4 a to 4d before driving the sheet into the ground also if necessary after the adapter has been removed the member 16 of the attachment 17 is affixed to e g the pile driver and the channel member 15 positioned over the top of the support sheet so that the top fits into the mouth of the channel the support sheet is then driven to ground level after the support sheet is at the required depth if required a second and any subsequent support sheet is driven into the ground overlapping the first support sheet as illustrated in fig6 in the building element illustrated in fig7 the rectangular sheet 1 pleats short sections 12 a b and holes 4 a b optional not illustrated are substantially as in the support sheet depicted in fig2 a casing 18 is affixed to the sheet 1 by any suitable means the casing comprising a double walled nylon mattress 20 held together at intervals by filter points 19 the casing is filled with for example fine aggregate concrete 21 by pressure injection until the mattress.