Cracks in your basement foundation wall can look unsettling, but not all of them signal a serious problem. Some cracking is the result of normal settling, while other cracks may indicate structural issues that require prompt attention.
We’ll explain the most common types of foundation cracks, what causes them, and when to monitor a crack versus call in a professional. Our guide also includes guidance from This Old House experts, including general contractor Tom Silva and landscape contractor Roger Cook.
Types of Basement Foundation Wall Cracks
Basement foundation wall cracks come in various forms, and each type can tell a different story about the structural health of your home. The direction and shape of a crack can reveal what’s happening behind the wall, making it one of the most important clues when assessing foundation damage.
We’ll break down the most common types of foundation cracks, their causes, and their implications.
Horizontal Cracks
Horizontal cracks often appear in basement walls and can indicate significant pressure from the soil outside the foundation. They are typically more concerning than vertical cracks and often require a professional inspection.
- Causes: Horizontal cracks are usually caused by the lateral pressure exerted by the soil surrounding the foundation. When soil becomes saturated with water, it expands and pushes against the foundation walls, creating horizontal cracks.
- Implications: If left unaddressed, horizontal cracks can lead to bowing or bulging walls, compromising the foundation’s structural integrity. This scenario may require substantial repair work, including wall reinforcement or foundation rebuilding.
Vertical Cracks
Vertical cracks run up and down the wall and are usually less severe than horizontal cracks. However, they can still indicate underlying issues that need addressing.
- Causes: These cracks often result from the home’s natural settling over time. Other causes may include concrete shrinkage or minor shifts in the foundation due to temperature changes.
- Implications: Vertical cracks are generally less problematic but can still allow water to seep into the basement, leading to moisture issues and mold growth. Sealing these cracks immediately can prevent further water intrusion and maintain the basement’s dryness.
Diagonal Cracks
Diagonal cracks can appear at various angles and may be more challenging to diagnose. Their implications often depend on the direction and width of the crack.
- Causes: Diagonal cracks typically form due to differential foundation settling, where one side of the house settles faster than the other. External factors like expansive soil, tree roots, or improper drainage can contribute to this uneven settlement.
- Implications: Diagonal cracks can indicate structural issues that, depending on their severity, may require intervention. While smaller cracks may be monitored and sealed, larger ones might necessitate professional evaluation and repair.
More Common Causes of Foundation Cracks
Various factors contribute to the formation of basement foundation wall cracks. Understanding these causes can help you take preventive measures to protect your foundation.
- Poor construction practices: Inadequate construction techniques or low-quality materials can compromise the foundation’s strength and make it more susceptible to cracking.
- Soil movement: Expansive soils that swell when wet and shrink when dry can create significant pressure on foundation walls. This movement causes stress and leads to cracks.
- Temperature fluctuations: The freeze-thaw cycle in colder climates can cause the expansion and contraction of soil and foundation materials, resulting in crack formation. Silva says that poor drainage can trap water in the soil around your foundation. When that water freezes, it expands and increases pressure on the walls, which can lead to cracking over time.
- Tree roots: The roots of large trees planted too close to the house can grow toward the foundation, exerting pressure and causing cracks to develop over time.
- Water pressure: Excessive groundwater or poor drainage around the foundation can increase hydrostatic pressure, pushing against the walls and causing cracks. Silva says that poor drainage can trap water in the soil around your foundation. When that water freezes, it expands, increasing pressure on the walls and potentially leading to cracking over time.
Identifying Foundations With Serious Structural Issues
While some cracks are natural and won’t affect your home’s foundation, others point to more severe structural concerns that require immediate attention.
Silva advises homeowners to watch for changes over time. Cracks that appear suddenly or continue to grow in width or length can signal more serious structural problems and should be evaluated by a professional.
Look for the following signs:
- Bowing walls: Any noticeable inward bending or bowing of foundation walls is a serious issue that requires professional inspection.
- Repeated repairs: If cracks reappear after being fixed, the underlying problem has not been addressed, and your foundation could be at risk of further damage and insecurity.
- Width of cracks: Cracks wider than 1/4-inch cause concern and likely indicate significant structural stress.
Professional Evaluation and Repair
If you identify any warning signs, consult a foundation specialist or structural engineer immediately. They will conduct a thorough inspection to diagnose the issue and can recommend the appropriate repair solutions. When cracks show signs of movement or structural stress, a professional evaluation is the safest way to determine the underlying cause and the appropriate repair.
- Inspection: A professional will assess the foundation’s condition, determine the cause of the cracks, and evaluate the overall structural health of the home.
- Repair solutions: Depending on the severity of the problem, recommended repairs may include wall stabilization, underpinning, or rebuilding sections of the foundation. The goal is to restore structural integrity and prevent future issues.
Structural engineer Jim Graham, who assesses foundation cracks for This Old House, follows the guidelines below to determine which cracks need attention and which don’t.
How Wide Are the Cracks?
On a poured foundation, a web of hairline cracks or widely spaced vertical cracks less than 1⁄8 inch wide generally means the concrete shrank too much as it cured. These can usually be left alone unless they grow wider or leak water. Cracks 1⁄8 inch wide or wider deserve a closer look.
What’s the Orientation?
Horizontal cracks indicate that the soil exerts enough pressure on the wall to make it bulge inward. They’re often accompanied by diagonal cracks in poured foundations or stair-step cracks in block foundations.
Diagonal or stair-step cracks without horizontal fissures may mean that the top of the foundation is bowing inward because it’s not properly connected to the house framing or that the footings are settling unevenly. Any of these cracks could signal the need for major structural repairs. Call in a structural engineer to determine their cause and prescribe a professional fix.
Is Water Getting In?
Graham recommends sealing stable but leaky cracks in poured foundations with epoxy (shown above) and injecting polyurethane foam along the crack’s entire length. For block walls, he goes outside, excavates the existing soil, adds crushed stone to improve drainage, and slopes the grade away from the foundation for at least 10 feet. Both approaches should be handled by a pro who specializes in basement waterproofing.
Preventive Measures To Protect Your Foundation
Taking proactive steps can help minimize the risk of foundation cracks and maintain your home’s structural integrity. Here are some effective preventive measures:
Proper Drainage
Water should always be directed away from the foundation. This prevents soil saturation and hydrostatic pressure, which, when too close to your home, can cause cracks in your walls.
Cook recommends extending downspouts several feet away from the foundation and ensuring the surrounding soil slopes away from the house to keep water from collecting near the walls.
- Gutters and downspouts: Keep gutters clean and make sure downspouts extend at least 5–10 feet away from the foundation to direct water away from your house.
- Sloping: Ensure the ground around your home slopes away from the foundation to prevent water from pooling and seeping into the soil.
Soil Management
Maintaining stable soil conditions around the foundation can reduce the risk of cracking.
- Landscaping: Avoid planting large trees or shrubs too close to the house. Their roots can exert pressure on the foundation, leading to cracks.
- Watering: During dry periods, water the soil around your foundation to maintain consistent moisture levels and prevent shrinkage.
Regular Maintenance
Regular inspections and maintenance can help you identify and address foundation issues before they become significant problems or hazards.
- Monitoring: Regularly inspect your basement walls for signs of new cracks or changes in existing ones. Note any widening, lengthening, or new cracks.
- Sealing: Use a concrete patching compound or hydraulic cement to seal minor cracks as soon as you notice them, preventing water intrusion. Always check the areas you have sealed with concrete or cement to make sure no new cracks show up. Otherwise, you may have a more serious structural problem.
Finding a Foundation Professional
Knowing when to seek professional help is essential for effectively addressing basement foundation wall cracks. A few telltale signs you’ll want to find a professional are if you notice water seepage or severe cracks along your walls.
Any cracks that let water into the basement should be professionally sealed to prevent future moisture issues and structural damage. If the cracks along your walls are wider than 1/4-inch, span in multiple directions, or show signs of bowing or bulging walls, you’ll want to contact a professional immediately.
Depending on the severity of cracking along your walls, you’ll want to find a professional with significant experience in foundation repair. A reputable professional will thoroughly inspect your foundation and provide a clear, itemized estimate for any recommended repairs.
Cost of Foundation Crack Repairs
The cost of repairing foundation cracks can vary significantly depending on the severity of the damage and the repair method required.
Minor Crack Repairs
For minor hairline cracks that do not pose a structural threat, repairs are typically straightforward and less costly. The most common repairs for small cracks are sealing and patching, each of which we’ve expanded on in detail below.
- Sealing: Sealing small cracks with epoxy or polyurethane can cost between $1.50 and $12 per linear foot. This method helps prevent water intrusion and further cracking.
- Patching: Using concrete patching compounds to fill and seal minor cracks can range from $1.50 to $12 per crack, depending on the size and number of cracks.
Moderate Crack Repairs
Moderate cracks that indicate some structural movement but not severe damage may require more extensive repair techniques. Carbon fiber straps and helical piers are common repair methods for slightly larger cracks.
- Carbon fiber straps: Installing carbon fiber straps to stabilize cracked walls can cost between $85 and $250 per strap. This method reinforces your wall without the need for invasive construction.
- Helical piers: Helical piers are installed to support and level the foundation for differential settlement issues. This repair typically ranges from $1,000 to $3,000 per pier.
Major Structural Repairs
Severe foundation issues compromising a home’s structural integrity will require significant repairs, which can be more costly. Underpinning and wall reconstruction are two common repair techniques for damaged foundations.
- Underpinning: Underpinning involves strengthening the foundation by extending it to more stable soil levels. This method can cost between $1,000 and $3,000 per section of the foundation.
- Wall reconstruction: In extreme cases where walls are severely bowed or damaged, partial or complete wall reconstruction may be necessary. Depending on the scope of the work, this extensive repair can cost from $1,000 to $5,000.
Note: The cost data featured in this section was sourced using pricing estimates from Angi, unless otherwise noted.
Our Conclusion
Not all foundation cracks require immediate repair, but they should never be ignored. Small cracks can often be monitored or sealed, while larger or changing cracks may point to more serious structural issues that need professional evaluation.
Paying attention to a crack’s size, direction, and progression can help you determine the right course of action and avoid more costly repairs down the line. Regular inspections and proper drainage can go a long way in protecting your foundation and maintaining your home’s structural integrity.
