There are two main types of modern residential foundations – poured concrete and masonry. Both are strong and reliable but either can be subject to movement and damage caused by pressures in the soil outside them.
When exterior pressures exert force on a poured concrete wall, the most common result is cracking. When the damage is minor, the cracks occur at random spots in the wall and can be repaired by injecting them with expanding polyurethane. Major damage is indicated by severe cracking along the sides and across the upper corners and the wall must be stabilized to repair it.
When a masonry wall, most commonly concrete block, is pushed inward by exterior pressures, the damage is usually seen by a bowing at or near the center of the wall. The bowing is usually accompanied by cracking of the mortar joints between blocks and, in serious cases, the blocks may shift out of the vertical plane of the wall.
Straightening a bowed foundation wall is not always possible so stabilizing it is the more common approach. Sometimes the traditional straightening process can be used in conjunction with modern stabilization methods.
The traditional approach to straightening a bowed foundation wall is to install one or more wall anchors in the damaged area. This process begins by burying a large steel plate vertically in the ground in undisturbed soil outside the foundation.
Then, a hole is drilled through the foundation wall, a long threaded steel rod is passed through a smaller steel plate and then through the hole.
The rod is then threaded through a hole in the buried plate outside and is tightened from the interior, using the resistance of the outside plate to begin pulling the wall back to plumb.
This approach can work but requires regular maintenance and tightening by the homeowner after installation and its success can depend on the stability of the soil outside the foundation.
For those reasons, it is often preferable to stabilize a bowed wall by using either steel or carbon fiber to lock it in place and prevent further movement.
If the bowing wall is detected early, before movement has exceeded two inches out of plumb, carbon fiber is the recommended repair method.
When the damage is more severe and the wall has bowed more than two inches out of plumb, channel steel is the preferred method of stabilizing the wall.
For carbon fiber repairs, engineering data is used to calculate the number and placement of strips. The wall is ground smooth at each location and a 12-inch wide carbon fiber strip is applied to the wall with industrial-strength epoxy and rolled under pressure to ensure a strong bond.
The lateral strength of the carbon fiber strips holds the wall in place and stabilizes it against any further bowing.
When greater movement has occurred, steel channel is used to stabilize the wall. The low-profile steel pieces are anchored to the foundation footing at the bottom and the top is bolted to a bracket mounted between floor joists. A jack screw device is used to tighten the top and bring the steel channel in contact with the wall along its entire length to provide complete stability.
Ascertaining which method of repair is best for a particular situation is the job of an experienced foundation repair contractor. At U.S. Waterproofing, our foundation repair experts use the latest techniques and relevant engineering data to repair bowed, cracked, dropped and sunken foundation walls for homeowners all over Chicagoland and northwest Indiana. Why not ask for our free advice?
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