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Foundation Cracks: What Is Normal and When to Worry

Typical cost range: $2,000 – $7,000

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Cracks and chips on the ruined foundation of the old building structure

Default Author Icon Written by Angela Bunt Updated 04/22/2024

Foundation cracks can compromise the structural integrity and resale value of your home. While some hairline cracks might be harmless, larger or growing cracks could indicate a serious issue. This guide will explain how to tell the difference—and what to do about cracks in your home’s foundation walls or concrete slab.

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Foundation crack repair costs between $250 and $800.

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What Are Foundation Cracks?

Foundation cracks are one of the most common foundation problems. They are fissures or breaks that appear in a home’s foundation walls or concrete slab.

Not all foundation cracks are cause for concern. The natural curing process of concrete can cause hairline cracks—less than 1/8 inch wide—to appear in the first few years after a home is built. However, larger cracks and those that grow over time could indicate a serious structural issue. Here are a few examples of foundational movement:

  • Settlement: Downward movement of the foundation
  • Uplift: Upward movement of the foundation
  • Rotation: Movement of foundation walls either inward or outward
  • Bulging: Part of the foundation wall protrudes outward from the rest of the wall.

If you notice new or expanding cracks in your home’s foundation, it’s worth paying for a foundation inspection. Hire a structural engineer or other qualified professional to evaluate the cause and severity of the cracks, and complete any recommended repairs as soon as possible. Early detection and intervention are crucial to prevent further damage.


What Are Problems with Different Types of Foundations?

Different types of foundations can have unique problems. Knowing your foundation type and materials will help you make an educated assessment of any foundation cracks and decide when to call in a professional.

Basement

Crawl Space

Concrete Slab-on-Grade

Concrete Slab-on-Stem Wall

A basement is often defined as an area mostly below ground with a ceiling height of at least 7 feet. The basement floor is usually a nonstructural slab of concrete, though some basements have dirt floors.

In newer homes, basement foundation walls are typically made of poured concrete. Older homes may feature brick or stone foundation walls instead.

A crawl space is an area below the living areas with a ceiling height of less than 7 feet. The crawl space floor is usually soil. Crawl space foundation walls are typically made of concrete blocks or bricks.

A slab-on-grade foundation is built by removing the topsoil, leveling the soil, and pouring concrete on top. The concrete may be a thick slab of uniform depth, known as a mat slab. Mat slabs are used only in warm climates where the frost line is near the surface.

Cold climates require a monolithic slab. For this type of slab, footings are dug around the perimeter of the building to below the frost line. Then a thin, nonstructural slab of concrete is poured over the rest of the foundation.

A slab-on-stem wall foundation is built by digging footings around the perimeter of the building to below the frost line. Walls are built on the footings to a point where the foundation is level and high enough to allow water to drain away from the foundation. The area inside the walls is backfilled, and a thin slab of concrete is poured on top.

The concrete may be thicker at load-bearing points inside the walls, but aside from these points, the rest of the slab is not considered a structural load-bearing element. Garage floors in basement foundations are often concrete slabs-on-stem walls.

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What Are Common Causes of Foundation Cracks?

Most foundation cracks are caused by soil movement. However, natural disasters and construction problems can also play a role. Here’s a complete list of possible causes:

  • Construction additions: Adding significant weight to your home through extensions or renovations can put additional stress on the foundation.
  • Frost heave: In freezing climates, water in the soil expands when it turns to ice, pushing upwards and potentially lifting or shifting the foundation.
  • Improper grading: If the land around your home slopes towards the foundation, it can cause water to pool and increase the soil pressure.
  • Moisture fluctuations: Drought and flooding—or even excess water from poor drainage—can cause the soil to expand or contract, putting stress on the foundation.
  • Plumbing issues: Leaky sewer or water lines can saturate the soil and trigger foundation movement.
  • Poor soil composition: Clay-rich soils are particularly prone to expansion and contraction, increasing the risk of foundation cracks.
  • Seismic activity: Earthquakes can cause significant stress on foundations, leading to cracks or more serious damage.
  • Tree roots: As tree roots grow, they can exert pressure on the foundation, causing cracks and displacement.

What Are Other Indicators of Foundation Problems?

Here are some other signs that may indicate a foundation problem. Note that these symptoms can have other causes, too.

Windows and doors that once operated properly now stick, rub, or do not open or close properly.
Floors that were once level are now noticeably out of level. You can test if your floor is level by placing a marble on it. If it rolls, the floor is out of level.
Cracks appear at the corners of door frames and window frames, especially if the cracks are wider at the top.
Gaps appear between the baseboards and flooring, especially if the gaps are wider at some points.

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Concrete Slab Cracks Vs. Foundation Wall Cracks

While both concrete slab cracks and foundation wall cracks may appear concerning, their significance and underlying causes differ. Here’s what homeowners should know about each:

Concrete Slab Cracks

Some homes are built on a horizontal concrete slab. Hairline cracks that haven’t changed in size, do not allow in water, and show no vertical displacement are often cosmetic and require no immediate action. In areas with extreme temperature variations, cracks may form as the slab expands and contracts.

Wide cracks, growing cracks, or cracks accompanied by other signs of a foundation problem may warrant a professional inspection. These cracks may be caused by uneven settling of the soil beneath the slab, moisture fluctuations, poor soil compaction, or tree root growth.

Foundation Wall Cracks

Many homes have foundation walls rather than a concrete slab. Cracks may appear in these walls due to seismic activity or poor construction. Uneven settlement or water pressure from the surrounding soil can also put stress on the foundation walls.

Even seemingly minor cracks in foundation walls require professional assessment. They are much more likely to indicate a serious structural issue than the cracks that appear in concrete slabs. Depending on the severity and cause, repairs might involve crack injections, underpinning, wall reinforcement, or more extensive interventions.


Questions to ask

When evaluating cracks in concrete slabs that do not qualify as hairline or shrinkage cracks, you will need to take extra steps to assess the situation. Use these four questions to help guide you through the process.

Foundation cracks can cause cosmetic and functional issues in areas intended for vinyl, tile, wood, or laminate floor coverings. Cracks with vertical displacement can cause cracks in tile and grout and squeaks in wood or laminate floor coverings.

Size matters when evaluating concrete cracks. The National Association of Home Builders (NAHB) standard for cracks in interior slabs requires repairing cracks that exceed 3/16 inch wide or high (vertical displacement). State regulators may have different standards.

Although smaller cracks can be patched, the patch may be more noticeable than the original crack. The patching material may also crack or become dislodged.

Cracks with vertical displacement of 1/4 inch or more in driveways, walkways, and patios can create a trip hazard. Extra care should be taken if children or those with reduced mobility regularly use the concrete slab.

Water can damage materials used to build a house, causing mold or mildew growth. Any crack that admits water should be evaluated and sealed. In addition to sealing the crack, be sure to identify the source of the water and eliminate it. Sealing a crack without addressing the water source can lead to more significant foundation problems.

Evidence of ongoing crack activity can greatly impact how best to deal with the problem. For example, when a crack appears where prior repairs have been attempted, it can signify continuing activity. It can also be a sign of a poor repair job or the normal aging of the repair material.

Crack monitoring devices exist, but they often are not practical on slab cracks, and they usually require monitoring over a long period.


Questions to ask

Evaluating a foundation wall crack is similar to evaluating concrete slab cracks. Use these six questions in your evaluation of foundation wall cracks.

Evaluating a crack in a concrete foundation wall is often different from assessing a crack in a concrete block or brick foundation wall. For example, a stair-step crack only in the mortar between concrete blocks or bricks may be less of a concern than a crack that runs through the concrete blocks or bricks. It usually takes more force to crack blocks and bricks than to crack mortar.

Crack location and direction make a difference, too. For example, a crack in the upper area of the foundation wall may be nothing more than damage from hen the foundation was backfilled. A long horizontal crack near the middle of the wall (vertically) may indicate pressure on the wall from the soil. A long diagonal crack may indicate foundation settlement or uplift, especially if the crack is wider on one end.

The NAHB standard for cracks in foundation walls requires repairing cracks that exceed 1/4-inch wide. State regulators may have different standards. Crack repair may be as simple as patching, but the proper method depends on the cause of the crack.

Cracks sometimes occur as a result of other foundation problems. A crack associated with other foundation problems may be more of a concern, regardless of the crack size, location, and direction. Carefully evaluate the entire foundation wall, not just the crack.

Any crack that admits water is a cause for concern. The water source should be identified and corrected before dealing with the crack.

Determining whether a foundation wall crack is active can be difficult. Though there are ways to evaluate crack activity, we recommend leaving this task to a professional.


How Much Does it Cost to Fix Foundation Cracks?

The cost to fix a foundation crack depends on the cause and severity of the issue, as well as the type of foundation you have. Hairline cracks can cost as little as $250* to repair with epoxy or polyurethane foam. Larger cracks are more serious but may still only cost about $800 to fix. You can see one method of fixing concrete foundation cracks in the video below:

If the cracks turn out to be merely one symptom of a bigger foundation problem, you could end up paying thousands of dollars. Replacing or repairing a severely damaged foundation can cost $20,000 or more. A structural report alone costs $300–$1,000. For wet cracks, you may also need invest in a drainage system ($2,800–$6,500) and/or waterproofing ($2,000–$6,000).

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*Costs are sourced from contractor estimates used by Angi, as updated in November 2023.


How Can You Avoid Foundation Problems?

The best way to deal with foundation problems is to avoid them. The following suggestions can help you avoid the vast majority of foundation problems and can help keep your basement and crawl space dry.

Slope the soil away from the foundation. The ground should slope at least 6 inches in the first 10 feet from the foundation. This method helps keep the soil near the house dry. Hard surfaces, such as driveways and porches, should slope away from the foundation at least 1/4 inch per foot.
Keep gutters and downspouts clear and in good condition. Slope the gutters toward the downspouts. Use splash blocks or downspout extensions to discharge water at least 5 feet from the foundation. If you have to replace your gutters, the average cost for gutter installation is $1,700–$3,100.
Install irrigation or drainage systems. Maintain them properly so they continue to discharge water away from the foundation.
Install foundation plants. Choose plants that will remain at least 1 foot (preferably 2 feet) from the house when the plant is fully grown. This will help keep irrigation water away from the foundation and help prevent damage to the house wall coverings.
Plant trees a good distance away. While uncommon, tree roots can damage the foundation. Tree branches can damage the roof covering.
Installing good soil under and around the foundation. Properly compacted soil with good load-bearing capacity can reduce foundation problems when the house is built. The ideal soil also lets water drain through if it gets wet. Coarse sand, gravel, stable clay, and mixtures of these are examples of good soil. Avoid soil that is high in organic materials or made with unstable clay.

Is Fixing Cracks in Concrete Worth it?

Evaluating foundation problems can be challenging, even for professionals who see them every day. While some cracks can be ignored, others will require time and money to resolve the issue. Remember, the general guidelines in this article are not a substitute for professional training and experience.

If you are concerned about a foundation problem, we recommend calling a professional, such as a structural engineer. The cost to repair a foundation typically increases the longer you wait, so the recommendation is to fix them sooner rather than later.


FAQs About Foundation Cracks

How can you tell if a crack is structural?

It can be difficult for homeowners to tell if a crack is structural. Look for signs like uneven floors, leaning walls, or a crack wider than 1/4 inch. It’s best to consult a structural engineer to assess any foundation cracks, diagnose the cause, and recommend repairs.

Can you fix a foundation crack yourself?

Although you may be able to fix cosmetic foundation cracks yourself, DIY repair is risky and could make the problem worse. Foundation cracks may indicate a serious structural issue that requires professional evaluation and repair.

Is it normal to have a crack in your basement foundation?

Hairline cracks in a concrete foundation are common and may not be serious. These cracks often occur within the first couple of years as the concrete cures. However, cracks that are larger, diagonal, or actively growing warrant professional evaluation.

Does homeowners insurance cover foundation crack repair?

Homeowners insurance does not typically cover foundation crack repair. The exception would be if the cracks were caused by a covered peril, such as a falling tree. Consult your policy or insurance agent to learn what events and types of damage your policy covers, and consider investing in separate flood or earthquake insurance for more protection.

Should I be worried about buying a house with foundation cracks?

Whether you should be worried about buying a house with foundation cracks depends on the cause and severity of the problem. Hire a structural engineer to perform a foundation inspection, then weigh the cost of repair and risk of future issues. Don’t be afraid to negotiate a concession or walk away if necessary.


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