Braces vs. Tie-back Anchors: Special Considerations for Walkout Basements

What do walkout basements, basement garages, raised ranches, and split-level homes have in common? These structures have exposed foundation walls—i.e. walls that are not surrounded by dirt. And when foundations in these structures experience lateral movement, the proper repair may be tie-back anchors instead of vertical I-beam braces. Choosing the proper repair system is critical, or you may not prevent further movement.

The Mechanics of Braces and Tie-Back Anchors

When a foundation wall is pushing in, two of the most commonly prescribed repairs include (1) vertical I-beam braces and (2) tie-back anchors (sometimes called “deadman anchors”).  Although these systems both solve the same problem (i.e. preventing further inward movement), they do so in very different ways.

Let’s start with the mechanics of each system. Vertical I-beam braces are mounted to the foundation wall at both the base and the top. The base of each brace is anchored in the concrete foundation floor. The top of each brace is attached to the floor joists overhead using special mounting brackets. Exemplary braces and connection points are illustrated in the photographs below.

Seven braces are installed along a foundation wall (braces indicated by red arrows).

This exemplary top mount system attaches the brace to the floor system overhead.

The bases of these three braces are anchored in the concrete foundation floor.

Now, as the braced wall tries to push inward (you can read more about what causes lateral movement here), the braces resist that movement by pushing against the concrete floor and the floor joists, thus transferring a portion of the inward force through the floor system. In some instances, it is primarily the opposite foundation wall and the soil behind it that prevent the braced wall from moving further.

Tie-back anchors oppose inward movement in a very different way. While individual tie-back systems vary, the general concept involves running a rod through the foundation wall, anchoring one end of the rod to the inside of the foundation wall, and anchoring the other end of the rod in the soil some distance away from the home. The anchor attached to the inside of the foundation wall is tightened periodically, which pulls against the anchor out in the yard to create an outward force against the wall. The first diagram below shows two bowing foundation walls, and the second diagram below shows an exemplary tie-back system that has been installed to remedy the lateral movement. Now, as the anchored wall tries to push inward, the anchor out in the yard pulls against the surrounding soil to resist that movement.

Bowing foundation walls.

Figure reproduced with permission from Ram Jack Distribution, LLC.

Exemplary tie-back system.

Figure reproduced with permission from Ram Jack Distribution, LLC.

For purposes of this discussion, a key difference between braces and tie-back anchors is that a braced wall often relies on the opposite foundation wall (and the soil behind it) to resist inward movement, while an anchored wall uses anchors out in the yard behind the wall (and the soil around the anchors) to resist inward movement. In other words, an anchored wall does not rely on the opposite foundation wall for stabilization.

When to Use Tie-Back Anchors

Braces are generally less expensive than tie-back anchors, and when used in the appropriate circumstances and installed properly, braces are very effective.  But in some circumstances, due to the forces described above, braces may not prevent additional lateral movement.

Tie-back anchors may be necessary when you have exposed foundation walls, or in other words, foundation walls that are not surrounded by dirt on the exterior.  Exposed foundation walls are common in the context of walkout basements, basement garages, raised ranches, and split-level homes. 

Why might braces be problematic when you have exposed foundation walls? Let’s suppose you have a walkout basement and your “problem wall” (the wall that is pushing inward) is the basement wall at the front of the house. On the opposite side of the basement is the back wall through which you can exit to the backyard. This back wall is an exposed wall, because it is not surrounded by dirt on the exterior. Let’s suppose you install braces on the front wall that is pushing inward. Now, as the braced wall pushes inward, the braces push against the floor joists overhead. In turn, the floor joists push against the back wall on the opposite side of the basement. If there were soil behind the back wall, the wall wouldn’t budge—the soil is too heavy. But in this example, there is no soil behind the back wall. So when the inward force from the front wall is transferred across the basement to the back wall, the back wall pushes out. The foundation (and the house above it) is now racking toward the back wall. That’s a big (and potentially expensive) problem.

The photos below illustrate this scenario. This house has a typical walkout basement, with the exposed wall at the back of the house. At some point, the basement wall at the front of the house began pushing in, and braces were installed in an effort to prevent further movement. Over time, as the inward force from the front wall was transferred across the basement to the back wall, the entire house began racking toward the back wall. In the first photo, you can see that this caused the back wall to push out, as evidenced by the leaning wall and the large V-shaped crack. In the latter photos, you can see the main beam in the house is being pushed off its support post, illustrating that the entire house is being racked toward the back.

The back wall is pushing out, as evidenced by the leaning wall and large V-shaped crack.

The main beam is being pushed off the support post.

Close-up view of the main beam being pushed off the support post.

In this scenario, tie-back anchors would have been the appropriate repair. An anchored wall does not rely on the opposite foundation wall for stabilization and therefore does not cause racking in this manner.

As with most things, this is not a hard-and-fast rule. There are instances when it may be appropriate to use braces in conjunction with exposed foundation walls, provided that the forces described here are given due consideration.  Nonetheless, if you see signs of foundation movement in a home with exposed foundation walls, there is a good chance that tie-back anchors will be recommended.

If you or your clients have concerns about foundation movement in a home with exposed foundation walls, Schroeder Engineering would be happy to help. Contact us today for a foundation inspection.