Holes are dug below
the foundation grade beam wall and pilings. Generally, the
pilings are 8" in length and 4" in diameter. The are
forced into the ground using hydraulic pressure a maximum level as
decided by the repair company, until sufficient resistance is met, or
a minimum of 10 feet. Rigid steel pins are installed during the
driving process to secure alignment and added strength. A
concrete cap is placed on top of the pilings and foot long concrete
cylinders are next. Steel shims complete the process.
Shafts will be
drilled vertically or at an angle next to the foundation and the depth
can range from 6 to 20 feet. The shafts are then filled with concrete
and have a haunch at the top that usually measures approximately 2
feet square. The haunch will be located about 1 foot below the
foundation. Drilled piers can be good choice when it is
difficult to create holes for other type of foundation supports
directly below the foundation.
There are basically
two types of interlocking systems. The first uses rebar inserted
after the pilings are driven in place and then the rebar is cemented
inside the pilings. The second method is to glue or cement a
flexible steel cable in the lead cylinder with the remaining cylinders
threaded through the cable. The end of the cable is then glued
or cement to the top cylinder.
|There are two areas
that may needs supports, the perimeter wall which carries the majority
of the structure's weight and the interior piers that are used to the
support the underlying beam. The perimeter wall can be supported
the same ways as slab and the interior piers are generally concrete
blocks or 1 to 3 foot poured concrete columns. Floors tend to
sag when the interior piers are too far apart or there is no longer
contact between the pier and the beam.