Is That Bow in Your Retaining Wall Normal? (Here's Why It's Failing)

The Scenario

A homeowner recently asked:

"Is this retaining wall okay?"

The GardenOwl Diagnosis

The Assessment

You moved into a new home in 2022 and noticed a slight curve—a "bow"—in your retaining wall. You did the responsible thing and asked the builder, who waved it off as "no concern." Fast forward to 2025: that "slight bend" has become a noticeable bulge, vertical cracks are spiderwebbing through the mortar, and you are witnessing a classic case of The Hydrostatic Dam Effect. Here is the hard truth: The builder likely rode out their warranty period hoping you wouldn't push the issue, and now you are left holding the bag on a structural failure where the masonry is "screaming for help" against invisible water pressure. You suspect serious issues related to your yard drainage, but you aren't sure if this is just an ugly cosmetic issue or a structural disaster waiting to happen.

Here is the hard truth: The builder likely rode out their warranty period hoping you wouldn't push the issue. Now, you are left holding the bag on a wall that is slowly failing.

The Trap: Ignoring Hydrostatic Pressure

Masonry is strong, but it has a fatal weakness: it does not bend. Stone, brick, and concrete have high compressive strength (they can hold heavy weight) but terrible tensile strength (they snap when stretched or bent).

The force pushing your wall outward is called hydrostatic pressure.

When it rains, water saturates the soil behind that wall. Water weighs roughly 8.34 pounds per gallon. If that water has nowhere to go because the soil is heavy clay or there is no drainage pipe, it builds up immense pressure against the back of the wall. Eventually, that pressure exceeds the strength of the mortar, and the wall bows out. The cracks you see are the masonry screaming for help.

This is a classic case of Why Your Brick Wall is Wet: The Hidden Danger of High Gravel—except in your case, the danger is invisible water trapped underground.

The Solution: Excavate and Drain

You cannot fix this with a patch kit or by pointing some new mortar into the cracks. That is like putting a band-aid on a broken leg. You have to relieve the pressure.

1. The "Autopsy" Excavation

Your instinct to dig is 100% correct. You need to excavate the soil directly behind the bowed section. You don't need to dig up the whole yard, but you need to clear a trench about 12 to 18 inches wide right up against the back of the stones, down to the footing.

2. The Smoking Gun

When you dig, look at what is touching the back of the wall.

• Good Scenario: You find clean, angular gravel and a perforated pipe.
• Bad (Likely) Scenario: You find heavy dirt or clay packed right up against the stone.

If you find dirt touching the wall, that is the cause of the failure. Clay soils expand when wet and act like a hydraulic press against your hardscape. For more on how soil types affect drainage, check out this guide on soil health and drainage.

3. The Drainage Fix

A proper retaining wall needs a "chimney" of drainage. This involves:

• Perforated Pipe: A 4-inch perforated drain pipe at the very bottom, encased in a fabric sock to keep dirt out.
• Clean Gravel: Backfilling the space behind the wall with #57 stone (clean, angular gravel). This allows water to drop straight down to the pipe and flow away, rather than pushing against the wall.
• Filter Fabric: Placing landscape fabric between the gravel and the soil (not the wall!) to prevent dirt from clogging your gravel chimney.

If the wall has already cracked and bowed significantly, simply removing the dirt might not snap it back into place. The mortar bonds are broken. You may need to deconstruct the bowed section and re-stack it. If the slope allows, you might even consider a tiered approach to reduce the load, similar to the strategy in Retaining Wall on a Steep Slope: Where You Can Dig.

Visualizing the Result

Before you start ripping out stones or hiring a mason, you need a plan. If the wall needs to be rebuilt, do you want the exact same wall? Or would a tiered slope with native plantings be more stable and attractive? Sometimes, the best fix is to Skip the Retaining Wall entirely and grade the land differently.

This is where planning saves you money. If you want to test this on your own yard, upload a photo to our Exterior Design App and see what this design would look like in your space. You can visualize a corrected wall, a tiered garden, or a sloped bed before you ever pick up a shovel.