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Foundation Cracks in St. Louis: What They Mean and When to Worry

Have you started noticing new cracks in your basement walls or along the outside of your home and wondered if they are normal? Many homeowners across the St. Louis metro area ask the same question. Some cracks are cosmetic and relatively harmless. Others are early warnings of foundation settlement or structural problems that should be addressed quickly.

At Perma Jack of St. Louis, we inspect and repair foundations throughout St. Louis, St. Charles, Jefferson County, and surrounding areas. Not every crack is an emergency, but no crack should be ignored. Understanding what you are seeing is the first step in protecting your home.

In this guide, we will cover:

  • Why foundation cracks are common in our region
  • The most common types of cracks and what they mean
  • When to monitor, when to repair, and when to call a professional
Cracks in the foundation

Why Foundation Cracks Are Common in the St. Louis Area

Homes in and around St. Louis are built on a mix of expansive clay soils, fill soils, and older backfill. These soils are very sensitive to moisture changes. When they get wet, they swell. When they dry out, they shrink. Over time this movement can put a lot of stress on your foundation.

Common factors that contribute to cracking in our area include:

  • Expansive clay soils that shrink and swell with the seasons
  • Heavy spring and summer rains that saturate the ground
  • Drought periods that dry and shrink the soil away from the foundation
  • Poor grading or downspouts that dump water near the foundation
  • Normal concrete curing in newer homes

Older brick homes in the city, ranch homes in South County, and newer construction in areas like O’Fallon or Wentzville can all experience cracks caused by soil movement and settlement.

Foundation Wall Crack

Types of Foundation Cracks and What They Can Indicate

The direction, size, and location of a crack all offer clues about whether you are dealing with normal movement or a more serious foundation issue.

1. Hairline Shrinkage Cracks

What they look like:

  • Very thin, hairline cracks in poured concrete walls or floors
  • Usually vertical or slightly diagonal
  • Often appear within the first few years after a home is built

What they usually mean:

These are often related to normal curing and shrinkage of concrete. On their own, they are usually not structural problems. However, they can still let moisture seep through and may worsen over time if other issues are present.

When to be concerned:

  • The crack begins to widen over time
  • You see moisture or efflorescence (white mineral deposits) appearing along the crack

In older homes around Kirkwood, Webster Groves, and South County, these cracks often appear in plaster or drywall and widen over time.

2. Vertical Cracks

What they look like:

  • Cracks that run mostly straight up and down
  • Can appear in poured concrete or block foundation walls
  • May start as hairline and slowly widen

What they may mean:

Vertical cracks can be related to minor settlement or shrinkage. However, if they grow wider or occur in multiple areas, they can indicate differential settlement, where one part of the foundation is moving more than another.

When to worry:

  • The crack is wider than the thickness of a nickel
  • It is clearly widening or spreading
  • It leaks during heavy rain

3. Diagonal Cracks

What they look like:

  • Cracks running at an angle, often from the corners of windows, doors, or foundation openings
  • Sometimes wider at one end than the other

What they may mean:

Diagonal cracks are often associated with uneven foundation settlement. In finished areas, you may also see diagonal cracks in drywall above doors and windows. These are clues that part of the foundation is dropping or shifting more than the rest.

When to worry:

  • The crack is wider on one end
  • You also notice sticking doors, sloping floors, or gaps at trim
  • New cracks appear over a short period of time

These issues are especially common in areas like Chesterfield and Ballwin, where homes sit on expansive clay soils.

4. Stair-Step Cracks in Brick or Block Walls

What they look like:

  • Cracks that follow the mortar joints in a step pattern
  • Common in brick veneer and concrete block foundations

What they may mean:

Stair-step cracks are a classic sign of foundation settlement and movement. When the foundation shifts, the rigid brick or block walls above it respond by cracking along the mortar lines.

When to worry:

  • The cracks are growing or spreading
  • Sections of the wall appear shifted, bulging, or displaced
  • You see them on more than one side of the home

If you live in an older brick home in St. Louis city or in established neighborhoods like Kirkwood or Webster Groves, stair-step cracks are a very important sign that should be evaluated.

Horizontal cracks or bowing are serious and should be evaluated by a structural professional immediately.

5. Horizontal Cracks

What they look like:

  • Cracks running sideways along a foundation wall
  • Often appear mid-height in block or poured walls

What they may mean:

Horizontal cracks are often caused by lateral pressure from soil pushing against the wall. In our region, saturated clay soils, hydrostatic pressure, and freeze thaw cycles can all increase this pressure.

Horizontal cracks can be associated with:

When to worry:

Horizontal cracks are considered serious and should be looked at promptly. If you also see bowing, bulging, or inward deflection of the wall, you should contact a foundation specialist as soon as possible.

These can indicate one part of your home is sinking faster than another.

Sinking Foundation Repaired

When Are Foundation Cracks Mostly Cosmetic?

Some cracks are more about appearance than structure, especially if:

  • They are very thin and not changing
  • They appear only in interior finishes like drywall, not the concrete foundation
  • They do not leak or show signs of moisture

Even so, it is smart to keep an eye on them. Take pictures, note the date, and check periodically for changes in length or width.

When Cracks Mean It Is Time To Call Perma Jack of St. Louis

You should reach out for a professional foundation evaluation if you notice:

  • Cracks that are getting longer or wider
  • Cracks wider than about one eighth of an inch
  • Cracks that allow water to seep into the basement
  • Multiple new cracks appearing over a short period of time
  • Cracks combined with other warning signs such as:
    • Doors or windows that stick or do not latch
    • Floors that feel uneven or sloped
    • Gaps between walls and ceilings or baseboards
    • A chimney that is leaning or pulling away from the house

These signs often indicate active foundation settlement or soil movement, not just cosmetic changes.

How Perma Jack of St. Louis Addresses Foundation Cracks

Perma Jack does more than simply patch cracks. We look for the cause of the cracking and design a repair solution that addresses the underlying foundation problem.

Depending on what we find, our recommendations may include:

  • Steel push piers or helical piers to stabilize and lift a settling foundation
  • Wall bracing or anchor systems to support cracked or bowing walls
  • Foundation crack repair to seal and protect against water intrusion
  • Drainage improvements to help manage water and reduce soil pressure

All solutions are based on decades of experience with local soils and St. Louis weather patterns, and are designed to provide long term stability.

Concerned About Foundation Cracks? Start With a Professional Evaluation

If you have noticed foundation cracks in your St. Louis area home, do not rely on guesswork. An early evaluation can help you avoid more serious damage and higher repair costs later.

Perma Jack of St. Louis offers thorough foundation inspections and honest recommendations. We will explain what your cracks mean, whether you should be concerned, and what options you have to protect your home. Contact Perma Jack of St. Louis today to schedule a foundation evaluation and find out what your foundation cracks are really telling you.

All solutions are based on decades of experience with local soils and St. Louis weather patterns, and are designed to provide long term stability.