The piles are constructed in short lengths joined with steel dowel bars grouted into position so that piles of any length can be constructed. Pile sections are pushed into the ground by jacking against the underside of the existing foundation. When the required depth has been reached the pile is built up to the underside of the existing foundation and pinned up. The water table may be high precluding the use of the wall underpinning method. Piles are driven to the required depth without disturbing the existing foundation though half will have to be driven from inside the structure.
Excavation takes place to reveal the existing foundation.
At the pile locations holes are made in the brick walls. The piles are exposed, reinforcement straightened and then support needles constructed giving support the brickwork over. In some instances temporary needles of steel or precast concrete can be used to support the existing brick wall. The foundation may then be lowered using the wall underpinning technique but without the need for bay construction. The pretest method may be used with the traditional wall underpinning method.