Retaining wall cracks are often signs of serious structural stress, not just cosmetic flaws. In Missouri, where the soil expands and contracts dramatically due to moisture shifts and temperature swings, retaining walls are particularly vulnerable to cracking if they aren’t properly designed, drained, or maintained.
Homeowners across Missouri—especially in regions with clay-rich soils often face cracked, leaning, or bowing retaining walls within a few years of installation. In this article, we’ll break down the most common causes of these cracks, how to prevent them, and what maintenance steps you can take to protect your landscape investment.
What do cracks in a retaining wall actually mean?
Cracks in a retaining wall typically indicate structural movement, drainage issues, or pressure from unstable soil. Not all cracks mean failure, but some types should trigger immediate inspection.
- Vertical cracks often result from settlement or uneven soil compaction.
- Horizontal cracks are more serious and typically mean soil pressure is exceeding the wall’s capacity.
- Stair-step cracks in masonry or block walls may signal shifting or rotating soil masses behind the wall.
In Missouri, the risk is higher due to local soil conditions. According to the Missouri Geological Survey, clay-rich soils here can expand by up to 10% when saturated—exerting lateral forces that push retaining walls outward over time.
What are the main causes of cracking in Missouri retaining walls?
Is poor drainage behind the wall to blame?
Yes. Poor drainage is one of the leading causes of wall cracking. When water builds up behind the wall with nowhere to escape, it creates hydrostatic pressure that pushes against the structure until it cracks or bows outward.
Signs that drainage might be failing include:
- No gravel backfill or filter fabric
- Clogged or missing weep holes
- Lack of a French drain or perforated pipe behind the wall
If you’re seeing water stains, puddles, or moss near the base of the wall, it may be time to explore retaining wall service in Missouri.
Can Missouri clay soil really cause this much damage?
Yes. Expansive clay soils in Missouri are a major contributor to retaining wall failure. These soils swell significantly when wet and shrink during drought, causing continuous movement that stresses retaining walls from behind.
This movement is most problematic:
- In central and eastern Missouri where clay is abundant
- During spring and fall transitions when moisture content shifts
- When walls are built without deep footings or soil reinforcement
Walls that lack flexibility or reinforcement often crack under this natural pressure.
Is the wall design or construction possibly flawed?
Yes. Many cracked walls are the result of poor design, underengineering, or skipping critical construction steps. This includes:
- Using incorrect materials for soil conditions
- Building too high without geogrid or tiebacks
- Failing to include a proper base or footer below frost depth
In Missouri, walls over 3–4 feet usually require engineering due to soil pressure and seasonal freeze–thaw cycles.
Does freeze–thaw weather contribute to wall cracks?
Yes. Repeated freezing and thawing causes trapped water to expand, putting stress on the wall. This is especially true for:
- Poured concrete walls
- Older mortared stone walls
- Walls built without drainage or sealant
Hairline cracks caused by freeze–thaw cycles often widen if left unaddressed over several winters.
Can nearby tree roots damage a retaining wall?
Yes. Tree roots exert pressure on retaining walls as they grow, especially if planted too close. Roots also dry out soil unevenly and may clog or displace drainage systems behind the wall.
Homeowners should:
- Avoid planting large trees within 10–15 feet of a wall
- Monitor nearby trees for root expansion
- Remove roots if they’re visibly lifting or cracking nearby hardscapes
How can you prevent cracking in your retaining wall?
Are there drainage improvements that help?
Yes. Proper drainage is the single most important preventative measure. Every wall should include:
- A layer of washed gravel backfill
- A perforated pipe (French drain) behind the base
- Weep holes spaced every 4–6 feet
Water should always have a way to escape to relieve pressure.
What design elements make a wall more durable?
Walls last longer when they’re designed for site-specific conditions. This includes:
- Using geogrid for walls over 4 feet
- Ensuring footings reach below frost depth
- Building with reinforced block or concrete in high-pressure zones
Working with a builder who understands Missouri terrain can greatly improve long-term stability.
Should I redirect surface water away from the wall?
Yes. Surface water should never flow toward your retaining wall. You can improve grading and drainage by:
- Regrading slopes to divert water downslope
- Adding surface drains or swales
- Extending downspouts away from the wall base
What’s the best landscaping approach near retaining walls?
Avoid aggressive root systems and overwatering. Instead:
- Use low-root, drought-tolerant plants
- Install root barriers if trees are nearby
- Maintain a vegetation-free drainage strip at the top of the wall
What maintenance tips can help prevent cracks over time?
Should I inspect my wall regularly?
Yes. Seasonal inspections can catch issues before they become structural. Check for:
- New or growing cracks
- Leaning or bulging sections
- Water pooling at the base after rain
Walls that shift even slightly over time should be evaluated by a specialist.
Can I clean or maintain drainage components myself?
Yes. Homeowners can flush weep holes, check for clogged drains, and top off gravel if it has settled. Preventing moisture buildup extends wall life dramatically.
Is it okay to repair small cracks on my own?
Yes, but only if they’re minor. Use masonry crack sealant on vertical surface cracks less than 1/8 inch wide. But if you see horizontal cracks, gaps widening, or signs of leaning, it’s best to contact a retaining wall repair expert in Missouri.
Common Questions Retaining Wall Cracks in Missouri
Are retaining wall cracks always serious?
No. Not all cracks indicate structural failure. Hairline vertical cracks are often harmless, especially in concrete. However, horizontal or widening cracks should be investigated right away.
Can I seal the cracks and be done with it?
Yes and no. You can seal cosmetic cracks, but structural cracks often result from underlying pressure or drainage issues that must be corrected at the source.
Do properly built retaining walls still crack?
No, not usually. Retaining walls that are properly drained, reinforced, and maintained can last 20–50 years without developing major cracks.
Don’t Let a Small Crack Turn Into a Major Problem
Cracks in retaining walls are common in Missouri—but they’re not always harmless. From poor drainage and shifting clay soil to freeze–thaw stress and root pressure, the causes are often preventable with proper design and maintenance.
If your retaining wall is showing signs of distress, now is the time to act. A quick inspection could prevent a costly rebuild later.
Need help diagnosing cracks in your retaining wall? Our Missouri team Retaining Wall & Paving Solutions can assess the damage and recommend the right repair or rebuild approach for your specific yard conditions.