Retaining Wall Crack Repair: When to Fix and When to Worry

A retaining wall has one job, and it's a heavy one: holding back a hill of soil. So when you spot a crack in yours, it's natural to wonder if the whole thing is about to give way. Most of the time it isn't. But retaining wall crack repair is one area where it pays to be honest about the difference between a cosmetic crack and a wall that's losing the fight.

The usual culprit is water. Soil behind the wall gets soaked, gets heavy, and pushes. For small cracks on the cap or the top of a stable wall, a masonry crack filler keeps water from getting in from above. For a wall that's leaning or bulging, filler isn't the answer.

The Short Answer

Small, stable cracks in a retaining wall's cap, face or joints can be cleaned and sealed to keep water out, and blocked weep holes or drains should be cleared. If the wall leans, bulges, has growing or horizontal cracks, or soil is washing out through it, call a contractor or engineer, especially for taller walls or walls near driveways, buildings or slopes. Sealing those cracks only hides a failing wall.

Why Retaining Walls Crack

• Water pressure. Saturated soil is much heavier than dry soil. Poor drainage behind the wall is the most common reason walls crack and lean.
• Blocked weep holes or drains. Many walls have weep holes or a drain pipe at the base to let water out. When they clog, pressure builds.
• Freeze-thaw of wet soil and water inside the wall.
• Footing problems. A wall without a solid base can tilt or settle.
• Shrinkage in poured concrete walls, which causes thin vertical cracks that are often harmless.
• Roots from nearby trees pushing on the wall.

Types of Retaining Walls and Their Cracks

• Poured concrete: thin vertical cracks are often shrinkage. Horizontal cracks or a tilt are the concern.
• Concrete block (mortared): cracks follow mortar joints. Stair-step cracks suggest settling.
• Segmental block (stacked, no mortar): these don't crack so much as shift. Look for bulges, gaps opening between blocks, or blocks pushed out.
• Stone: loose stones and gaps are more common than cracks.

Cosmetic or Serious?

Usually cosmetic

• Thin vertical cracks in a poured wall that isn't leaning
• Cracks in the cap or top course
• A single open mortar joint

Call a pro

• Leaning, tilting or bulging anywhere along the wall
• Horizontal cracks across the face
• Cracks that keep widening
• Soil or muddy water coming through cracks or gaps
• A tall wall, or one supporting a driveway, structure or steep slope

Taller walls and walls holding up something important often need an engineered repair, and in many areas a permit. A leaning retaining wall is a safety issue, so don't put it off.

Fix the Drainage First

• Clear weep holes with a stiff wire or rod.
• Check the drain outlet at the ends or base of the wall and remove blockages.
• Redirect downspouts and sprinklers away from the soil behind the wall.
• Regrade the top so water doesn't pool behind the wall.

Choosing a Retaining Wall Crack Filler

• Cap and top cracks: a water-activated filler suited to masonry and concrete works on horizontal surfaces. The Crack Repair Filler by VALYA is ready to use, needs no mixing, and cures weather-resistant. The same product handles cracks in nearby walkways as an exterior concrete crack filler.
• Vertical face cracks: a non-sag masonry filler or patch.
• Mortar joints: fresh mortar for repointing.
• Don't seal weep holes or drainage gaps. They're supposed to be open.

For a broader look at wall cracks, see our cement wall crack filler guide.

How to Seal a Small Retaining Wall Crack

1. Clear the crack of soil, moss and roots with a screwdriver.
2. Brush and blow out the dust.
3. Make sure it's dry.
4. On the cap or top: fill the crack with the pointed applicator, level it, then mist lightly with water.
5. On the face: press a non-sag filler in with a putty knife and smooth it.
6. Let it cure and check the wall again after the next heavy rain.

Mistakes With Retaining Walls

• Sealing a leaning wall and hoping for the best
• Plugging weep holes while sealing cracks
• Ignoring water behind the wall
• Piling extra soil or parking vehicles near the top
• Planting trees right behind the wall

FAQ

Are cracks in retaining walls normal?

Thin vertical shrinkage cracks in poured walls are common and often harmless. Leaning, bulging or horizontal cracks are not.

Can I repair a leaning retaining wall myself?

No. A leaning wall is under too much pressure or has a footing problem, and it can fail. Have a contractor or engineer assess it.

Should I seal the weep holes in my retaining wall?

No. Weep holes let water out from behind the wall. Clear them instead.

What causes retaining walls to fail?

Most often, poor drainage. Water-soaked soil pushes harder than the wall was built to resist.

Wrapping Up

Retaining wall crack repair starts with drainage: clear weep holes, redirect water, and seal small cracks in the cap and face. Leaning, bulging or horizontal cracks mean the wall needs a professional.

For small cracks on caps and nearby walkways, take a look at the Crack Repair Filler by VALYA and see if it fits your project.