by Steve Shackett and Scott
Anderson
From the 1950s through the '80s — before poured concrete
became the norm — many homes in northern New England were
built with concrete block foundations. Unfortunately, block
isn't the best material for a long-lasting foundation in this
area. Frost pressure, melting snow, and heavy clay soil put a
lot of stress on block walls, and I see the resulting damage
every day. Our company, Tri-State Basement Systems in Berlin,
Vt., specializes in waterproofing and repairing leaking and
damaged foundations.
On a recent job, we were called to the home of a retired
couple. The long side of their house had bowed in about 3
inches in the center, and the short section of wall next to the
garage door had sunk several inches (see Figure 1). When cracks
in the plaster started showing up, they gave us a call.
| |
| Figure
1. Soil pressure pushed this block foundation
to the point of near collapse. Inside, the wall bows in
a little more than 3 inches at the center, pushing the
electrical panel with it. Note the sunken wall next to
the garage door. |
Two-Part Repair
The repair and stabilization plan developed by our estimator
called for two support piers to prevent the subsided footing
from sinking further and three wall ties to pull the bulging
foundation wall back in line.
To stabilize the
footing, we use a push-pier jacking system from Grip-Tite
Foundation Systems (877/474-7848,
www.griptite.com). Hydraulic rams powered
by a portable pump push steel posts into the ground until they
develop sufficient bearing capacity. At this point, L-shaped
brackets are bolted to the post and support the footing from
below. The system works in principle a lot like an automotive
bumper jack, except the lifting action is hydraulic rather than
mechanical. While smaller repairs like this one are more
common, we've also used the push-pier system to stabilize
entire foundations built on poor soil.
Ties. Wall ties, the other
half of the repair plan, are an inexpensive and effective
solution to buckled walls. A large metal plate on the inside of
the foundation wall and another below grade on the outside are
connected by a threaded rod. As the nut on the rod is
tightened, it gradually draws the plates closer together,
straightening the wall. It works similar to the rail bolts used
for joining sections of laminate countertop or handrail (Figure
2).
Figure 2. The Grip-Tite
system uses both anchors and push piers to stabilize problem
foundations.