Epoxy Injection

Cast in place concrete foundation walls which are inadequately connected to the floor system, or walls which are subjected to relatively high soil pressures, may fail and move inward. As they move inward they typically develop diagonal cracks at the ends of the walls which may wrap around the corners, and at least one vertical crack near the center. Epoxy injection of these cracks alone will not stabilize the foundation wall.

Carbon Fiber

Bracing a concrete foundation wall with carbon fiber straps is not a viable solution as the top of the straps are not, and can not be, connected into anything. Carbon fiber was developed to reinforce areas of excessive tension stresses within concrete structures, like bridges and buildings, typically in seismic zones and not to provide bracing for foundation walls.

Steel Braces

At the ends of the leaning concrete foundation wall, in the area of the diagonal cracking, the integrity of the wall is usually significantly compromised and requires full height bracing with steel beams, along with epoxy injection of the cracks, to restore the integrity of the wall. In areas where the integrity of the foundation wall has not been compromised, the connection between the floor framing and the foundation wall can be restored. One way we typically restore this connection is with steel angles bolted to the foundation wall and the floor joists. The size and spacing of the steel angles, and the required bolting, will vary depending on the height of the foundation wall and the height of the exterior grade.

Tie Back Anchors

There are situations where it may not be possible to brace the foundation wall with a connection to the floor framing. Similar situations exist with retaining walls. These situations require some type of anchorage back into the soil. These anchors are referred to as tie-back anchors.

Helical Tie Back Anchors

Helical anchors can be used as tie backs if you can embed them into the soil deep enough to provide adequate resistance and have them embedded beyond the failure plane of the soil. The failure plane is the area of soil which is moving with the foundation wall or retaining wall. If your anchor is embedded within that area it will do nothing to restrain the wall as it will move with the wall. Embedding helical anchors deep enough in tough clay, which is common in the Chicago land area, can be difficult as the force required to turn the anchor into the soil may exceed the mechanical limits of the anchor shaft. Before utilizing helical anchors as tie backs it is recommended that the soils be investigated by a geotechnical engineer.

It is also advantageous to have access to the back side of the foundation or retaining wall so that the hole cored through the wall only needs to be large enough to accommodate the anchor shaft and not the helical plate. The shaft can be placed through the wall and the helical plate installed on the back side with some excavation.

Concrete Deadman Tie Backs

In order to control the embedment of tie back anchors, and to assure they have adequate resistance, we use what is referred to as “concrete deadman”. A trench is excavated parallel to the foundation wall, beyond the failure plane of the soil, and set reinforcing steel bars in the trench. Holes are drilled through the foundation wall and galvanized threaded rods are run through the foundation wall into the trench. The trench is then filled with concrete. This system provides ample, predictable, economical, and reliable tie back capacity.

Drilled and Grouted Tie Backs

In some unique situations it may be necessary to install grouted tie backs. These are situations where access to the back side of the foundation or retaining wall is limited, the foundation or retaining wall is relatively tall, proper embedment depth of the tie back must be obtained, and high tie back capacities are required.

A grouted tie back is a hollow threaded rod which has a drill tip on the end. Sections are added as the tie back is drilled into the ground. The tie back is drilled through the retaining or foundation wall and back into the soil. As it is drilled in, cement grout is pumped down through the hollow center until it flows back out the bore hole in the wall and the threaded rod becomes cemented into the ground. Connections to steel plates and beams at the front of the wall can then be made.

Foundation Wall Push Back

In situations where the foundation wall has moved in excessively it may need to be pushed back to a plumb position prior to installing the permanent bracing. We typically recommend this if the wall is more than 2-1/2″ to 3″ out of plumb. Pushing the wall back does require excavation at the exterior to relieve the soil pressure. It is not possible to move a foundation wall back to a plumb position against the soil without removing the soil first.