Crack In Foundation? Common Types And Must-Know Fixes
Published Sept. 24, 2025
Discovering a crack in your home’s foundation is alarming. Is it a minor issue or a warning of something serious? Some cracks are a normal part of settling, while others signal significant structural problems. Knowing the difference is crucial for any homeowner. Don’t let uncertainty about a crack in the foundation keep you up at night—understanding what it means can save you stress and money.
In this article, we’ll examine common causes of foundation cracks. We’ll clarify how to tell a minor cosmetic issue from a serious structural threat. We’ll outline types of cracks and repair methods, from DIY fixes to professional reinforcement.
Crack In Foundation: What You Need To Know
A crack in the foundation is any split or fracture that appears in the concrete or block wall that supports your home. These walls form your basement or crawl space and are critical to your house’s stability. Cracks can vary widely in size, shape, and direction. Each type can tell a different story about what’s happening to your foundation.
Why Foundations Crack: Causes And Risk Factors
Foundation cracks can result from a combination of soil, water, and time. Key causes include:
- Settlement: After construction, a house naturally settles as its weight compresses the soil beneath it. This can cause minor cracks, which are typically not serious.
- Concrete curing: Concrete dries and hardens in a process called curing, where it gradually gains strength. During this process, it shrinks slightly. This can form small, thin cracks known as shrinkage cracks.
- Soil pressure: The soil around a foundation expands when wet and contracts when dry. This movement puts pressure on foundation walls. It often causes horizontal or diagonal cracks. These cracks result from hydrostatic pressure.
- Poor construction: Foundations can be prone to cracking over time. This often happens with inadequate soil preparation. Improper concrete mixes also contribute to this issue.
Cosmetic Vs. Structural Cracks
The key differences lie in the crack’s size, direction, and whether it’s growing. Cosmetic cracks are usually thin (under ⅛ inch), vertical, and don’t change. They often result from normal concrete curing.
Structural cracks are typically wider (over ¼ inch), horizontal, stair-stepped, or diagonal. These often indicate foundation movement or failure. Other signs include bowed walls or sticking doors and windows.
Common Types Of Foundation Cracks
Identifying the type of crack in the foundation is the first step in assessing its severity. Here are eight common types you might encounter.
Hairline
A hairline crack in the foundation is thin, often no wider than a strand of hair, and typically forms on poured concrete walls. They’re common in new homes and usually stem from concrete drying and settling during curing. These cracks rarely signal structural issues, but they should be monitored. If a crack widens or lets water through, seal it to prevent moisture problems.
Vertical
Vertical cracks run straight or nearly so. They’re usually wider than hairline cracks and result from foundation settling. These cracks rarely signal major structural issues, but they can let water enter your basement. One narrow vertical crack is usually not alarming, but watch out for moisture or widening.
Horizontal
Horizontal cracks, which run parallel to the floor, are usually a sign of serious structural problems. Pressure from the surrounding soil often causes these cracks, bowing the wall inward. A horizontal crack in the foundation weakens the wall and, if ignored, could lead to collapse. If you see a horizontal crack, call a professional immediately.
Diagonal
Diagonal cracks run at an angle of 30 to 75 degrees. They often point to differential settlement. This happens when one part of your foundation sinks faster than another. The uneven stress causes angled fractures. Like horizontal cracks, these are a serious concern and need a professional assessment.
Stair-step
These cracks appear in concrete block or brick foundations and follow the mortar joints in a “stair-step” pattern. They typically result from foundation settlement or moisture pushing against the wall. Stair-step cracks indicate a structural problem that needs expert evaluation.
Shrinkage
These small, vertical cracks occur as concrete cures and shrinks. They’re common in new homes (under a year old). They’re usually not structural but can let water in, so sealing them is a good preventive measure.
Expansion
Concrete expands in warmer temperatures. Without proper expansion joints, the concrete cracks under pressure. These cracks can deteriorate and lead to water intrusion or structural damage.
Settlement
Settlement cracks are caused by a house settling on its foundation. They can appear as vertical, diagonal, or stair-step patterns. Minor settlement is normal, but significant or ongoing movement can cause serious structural problems. Monitor these cracks for size and progression.
Foundation Crack Repair Methods
Once a crack is identified, the right repair depends on its type and severity.
Sealing And Caulking Small Cracks
For minor hairline or vertical cracks that aren’t structural, a straightforward repair is often enough. Use a high-quality polyurethane caulk or concrete sealant to fill the gap. This helps prevent water intrusion. A capable DIYer can usually manage this task.
Epoxy And Polyurethane Injections
For wider vertical cracks that leak, crack injection is a common professional repair. This involves injecting epoxy, a strong adhesive, or polyurethane foam, a flexible, expanding sealant, into the crack. The material fills the gap for a permanent, waterproof seal. Epoxy adds strength, while polyurethane provides flexibility for slight wall movement.
Structural Repairs For Serious Cracks
Horizontal, diagonal, or stair-step cracks mean deeper problems. Sealing these cracks won’t fix them. Here are common repair methods:
- Carbon Fiber Straps: Applied to the interior of a bowing wall, these straps stabilize and prevent further movement.
- Steel I-Beams: These beams are installed on damaged walls. They brace the walls against external soil pressure.
- Foundation Piers: Steel piers are used for settling foundations. They’re driven into stable soil or bedrock. This transfers the house’s weight and stabilizes the structure.
- Wall Anchors: Large steel plates are buried outside and connected by rods to the foundation wall. When tightened, they pull the wall back and hold it steady.
- Helical Tiebacks: Screw-like rods drilled into the surrounding soil at an angle to counteract pressure and straighten bowed walls.
- Shotcrete or Gunite Reinforcement: A thick layer of high-strength concrete is sprayed onto the interior of weakened walls for added structural strength.
- Underpinning: Underpinning is a procedure that extends the foundation deeper into stable soil or bedrock, which prevents further settlement and provides long-term stability.
- Slabjacking (Mudjacking/Polyjacking): For sunken slabs, grout or foam is pumped underneath to lift and level the concrete surface. Grout is a fluid, cement-like mixture, and polyurethane foam is an expanding material that raises the slab.
Add Expansion Joints
Thermal expansion can cause foundation cracks. A professional can fix this by cutting expansion joints into the concrete. These planned gaps allow the concrete to move without further damage.
Monitor And Maintain Over Time
It’s essential to monitor any cracks, even minor ones. Place tape over the crack or make marks at its ends. If the tape breaks or the crack extends beyond the marks, it’s an active issue. This requires professional attention.
Frequently Asked Questions
Can a crack in a concrete foundation be repaired by a DIYer?
It depends. Small, non-structural hairline or shrinkage cracks can often be repaired by a capable homeowner. Wider, horizontal, diagonal, or leaking cracks need professional evaluation.
How fast can a crack in the foundation of a house worsen?
The rate varies significantly. A crack might remain stable for years. It can also rapidly worsen after heavy rain or soil shifting. Regular monitoring is essential, especially for structural cracks that can deteriorate quickly.
Does waterproofing fix foundation cracks?
Waterproofing is important, but it isn’t a complete solution for structural cracks. Simply sealing a crack without reinforcing the wall doesn’t work. First, fix the root cause, such as pressure or settlement. Then, waterproof to prevent future moisture problems.
When To Call A Professional
Knowing when to contact a professional can truly save you thousands in the long run. Addressing foundation issues promptly prevents minor problems from escalating into costly, major structural damage.
Signs Of Serious Structural Damage
Get in touch with a repair specialist or structural engineer immediately if you notice the following:
- Any horizontal crack.
- A diagonal or stair-step crack wider than 1/8 inch.
- A wall that appears to bow or bulge inward.
- Multiple cracks in one area.
- Cracks that are actively growing.
Cost Vs. Risk Of Delaying Repairs
Delaying repairs to save money might seem wise, but it’s dangerous. Small structural issues left unaddressed will only worsen. As pressure on the wall increases, it could lead to catastrophic failure. Repairing a bowing wall now is far less costly than rebuilding a collapsed one later.
Choosing A Foundation Repair Specialist
When choosing a foundation repair specialist, look for a company with extensive experience in your area. They should be licensed, insured, and able to provide references from past clients. Get multiple estimates. Ask each contractor to explain their solution. Understand why it’s the best choice for your problem.
Protect Your Home: Act Early On A Crack In The Foundation
Your home’s foundation is its backbone, and even a small crack in the foundation can tell an important story about its stability. Hairline or vertical cracks may only need monitoring and sealing. However, horizontal, diagonal, or stair-step cracks signal a more serious problem. These indicate structural stress and should never be ignored. Acting early not only protects your safety but also saves you from costly repairs down the road.
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About The Author
Experience, exploration, and knowledge are the hallmarks of writer Rei Bayucca. Her dedication to crafting articles that both inspire and educate will leave you thinking long after you’ve finished reading.
