How To Repair a Cracked Retaining Wall

Quick Column Summary:

• Cracked concrete retaining wall on home
• Was steel installed, or installed incorrectly
• Fix with steel plates or helical wall anchors
• Get the right installer to do the job

DEAR TIM: Thirteen years ago, a long poured concrete retaining wall was installed when our home was built. We didn’t hire the builder and have come to discover he built the home and wall using poor construction methods. Believe it or not, there are no building code inspections in this part of my state. Do we have to tear down the retaining wall and start over? The soil here is a deep clay and I wonder if the wall is substandard and can’t hold the weight of the soil. What would have prevented the horrible cracks or minimized them? What are my repair options at this point? John O., Jefferson City, MO

DEAR JOHN: The issues you’re having with your retaining wall are very similar to those folks have with poured concrete and concrete block foundation walls. Based on the photos you sent me, I’ve got good news for you.Your retaining wall can be stabilized and hold back that clay soil for many many years! The best part is the work can be done in just one or two days. You do not have to tear down the wall and start over.

These are severe cracks in a poured concrete retaining wall. There are ways to stabilize the wall without tearing it down and starting over. Photo Credit: John Oliveras

There are towns very close to where I live in New Hampshire that have the same situation you have with respect to the building code. In the towns near me, the person applying for the permit signs a document saying he’ll build the house to code, but there are no inspections. There’s no doubt in my mind many many houses built under these conditions have significant code violations. I see them all the time here when I stop by construction sites.

When you couple that reality with the fact that the building code is a set of minimum standards, you have the perfect storm for future repair problems. Most people don’t realize that building a home to code is like getting a 70 percent on a test. It means you barely pass. Believe me, you can incorporate building practices and standards that far surpass the building code.

For example, the cracks in your retaining wall tell me the builder didn’t install vertical steel rods, or if he did he placed them in the wrong position, he didn’t use enough steel, or the steel used was the wrong size.

The clay soil pushing against the back of the wall does two things. It tries to tip the wall over and it can cause the wall to bend or bow in the center. This bending of the wall can also happen if the wall is being tipped over by the soil. Placing 5/8-inch diameter vertical steel bars 16 inches on center and that are about 2 inches away from the side of the concrete wall that’s in contact with the clay soil would have really helped to prevent the cracks. A structural engineer is the best person to design where the steel bars should be placed.

To repair your wall, you’re going to get in contact with several companies that specialize in repairing foundation walls. I’ve worked with these companies for years, and many have great methods that will stabilized the concrete wall.

One of the solutions may incorporate large galvanized steel plates that are placed on the exposed part of the retaining wall. A hole is drilled through the concrete wall and a long  threaded rod is driven through the wall and into the soil behind the wall. The contractor digs a hole and places another large plate in the soil at the other end of the threaded rod. The threaded rod is connected to both plates with large nuts.

The plate in the soil provides resistance as the retaining wall tries to fall away or tip over. Using a large wrench, you can tighten the nuts on the threaded rod and pull the wall back into position over a period of months.

I happen to prefer the use of helical wall anchors. These are giant screws that bore into the soil behind the retaining wall. When connected to the galvanized plates on the exposed side of the retaining wall, they not only will stabilize the wall, but the anchors can also pull the wall back into it’s original position.

Your contractor may want to dig behind the retaining wall in order to make some of the repairs. While it’s not always necessary to do this, it can help prevent future problems. If there’s not great drainage behind the wall, now would be the time to install it.

Once the wall is stabilized you can inject the cracks with concrete repair epoxy. If the concrete crack surfaces are clean or can be cleaned, the epoxy will bond with a ferocious grip. If you take your time installing this product you may be able to tool it and sprinkle on some fresh Portland cement powder to disguise the cracks.

When you interview contractors for this job, be sure to ask for references from three to five years ago. You want to talk to past customers who can attest the repair methods are working. A recent customer won’t be able to give you this valuable information.

Be sure you understand what the galvanized steel plates will look like. I have to admit they don’t look attractive. If you can get the contractor to space them out in such a way that the spacing is somewhat equal, you may be able to disguise them with some sort of  decorative iron work that covers the plates. You may even be able to have a shelf built that holds plants that can hide the plates. Put your creative hat on!

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