Why Retaining Walls Collapse?

Retaining walls serve a good purpose. They hold back soil, reinforce steep areas, prevent erosion and allow lower-level space to be effectively and safely used. Retaining walls are often used around basements or in residential landscaping as an easy way to utilize hills and space. 

Several reasons exist why retaining walls collapse. It could be the design wasn’t equivalent to lateral earth pressure, water pressure or freezing water, or soil shearing behind the wall. Things like poor load design, bad soil, and lots of groundwater all contribute to these failures. 

There are ways to prevent failures and rebuild a retaining wall. Read the article below to find out more. 

Common Reasons for Retaining Wall Failures

Behind the basic reasons listed above, there are root causes of retaining wall failures that come from bad design, create excessive soil loads, or amount to too much water. Here is a look at those root issues. 

Bad Construction

Most retaining walls fail due to construction errors and most of those errors are committed by homeowners trying to build the wall themselves. Miscalculations on depth and weight and bad grouting are just two of the errors homeowners make in a DIY retaining wall project. 

The underlying problem with homeowner projects is they are anxious to be done with the work. That leads to people taking shortcuts. Homeowners can do a lot of this work but must take it on to do it correctly with no shortcuts.

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Bad Footing

In short, your retraining wall wasn’t built with a good foundation. Many use dirt or gravel underneath the wall. The wall will lean or fail if it shifts or isn’t compacted. Some builders use capstones for the footing. That’s like wearing a size five shoe when you need a 10. The only way to fix this problem is a rebuild.

Bad Drainage

Drainage should be considered when putting in a retaining wall. Water that has no escape will rush against the wall, wearing it out. It will also create heavy soil that will push the wall over. Drainage issues are a common problem when it comes to retaining wall damage.

Bad Backfill

Soil creates the backfill for retaining walls. It needs to be correctly layered so water can move. 

Bad Materials

Softer stones may be cheaper but they crumble. Look at the kind of stone used in your retaining wall. You may need to go with a tougher stone in the rebuild.

Some builders use stones, bricks, or wood planks incorrectly. They put smaller top row pieces on the base and larger base pieces on top. 

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Bad Weight

Some people think a retaining wall is solid enough to handle extra weight like a deck. This isn’t true. Retaining walls aren’t meant to be support structures. 

A retaining wall is built for its purpose and anything that will be bearing weight needs to be built with that in mind.

Old Age

Older walls wear out. Stone can crack. The ground shifts and the backfill eventually make stones lean. This is not a rare occurrence. Stone and wood walls should last at least 40 years. Stone retaining walls should last at least 50 years. 

Some will last a century or more.

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Fixing a Retaining Wall

Even though homeowner construction errors can cause issues with a retaining wall, there isn’t a reason why you can’t fix it yourself. Unfortunately, any repairs are going to involve taking the wall apart. 

Remove any plants around the retaining wall. Start removing wall pieces.

Be sure to note and categorize the stones on how they were put together. You will want to put them back the same way unless the stones weren’t put together correctly in the first place. You will want to replace any failing stones too, so mark those to get some of the same type and size. 

Inspect the subgrade to figure out what is causing the problem. Look for tree roots, bad backfills, bad foundations, or a lack of compacted soil. 

That was the easy part. Now comes the challenge. 

Dig a little wider and deeper on the old footing. You will need some extra room to work with to properly fix your retaining wall. Spread a thick layer of gravel in the trench and pack it with a tamper. 

The first course of blocks should lay halfway deep in the trench. One block should be set every six feet or so for the length and be level. Use a rubber mallet to secure them. 

This is your footing so make sure the blocks are larger ones. Only larger blocks can support the entire wall.

It is important to use a level throughout the rebuild. You want each layer to be level as you go.

Otherwise, you end up with a haphazard-looking structure.

Lay landscape fabric along the wall’s base and back. Landscape fabric will help control weeds and adds a bit of solid security to the foundation. Backfill behind the first layer with gravel. It is probably best to use the crushed gravel as it can be compacted and fits nicely together.

You will want to compact gravel as you go to keep it secure.Set the next row of blocks by using channel connectors to line up channels. Don’t overlap face joints. 

Now, lay a perforated plastic pipe behind the wall and use gravel to backfill it. This will provide the drainage you need to keep water and heavy soil from pressing onto your wall. Drainage isn’t something you can skimp on. Perforated plastic pipes are inexpensive but save a world of problems later.

Lay the third row of blocks. Backfill with gravel. Keep doing this until the wall is the height you want. You may need to cut some stones or blocks with a wet saw to fit them perfectly with each other. 

Use construction adhesive on the top row of blocks and secure the cap pieces. Use a rubber mallet to even it. Replant the flowers and bushes you removed.

Read: What Can I Do With An Uneven Backyard?


How can you stop a retaining wall from collapsing?

You can add gravel or aggregate and compact it. Compacting fills in space in the soil and makes for a stronger foundation. 

What happens when a retaining wall fails?

A failed retaining wall leaves piled dirt from the collapse. This can be expensive to repair and cause significant landscape damage. 

What are the signs of a failing retaining wall?

Some signs that a retaining wall is failing are the wall cracking or bulging. The wall may lean or show that it’s shifting. There may be sunken areas around the bottom.

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What can you do with a leaning retaining wall?

You have two choices to fix the leaning problem. You can demolish it and rebuild it or call in a professional foundation repair company. 

Can you push a retaining back if it’s leaning forward?

No, you can’t push it back. You will need to first remove the dirt behind it. Then, you will need to reset the wall and add more soil or stabilizers. You may also need to repair damage and then add more backfill.

How will I know when it’s time to replace my retaining wall?

You’ll know it’s time when there are noticeable cracks in the wall or a separation between the part of the wall from the main structure. You may also notice water leaking through or over the wall.