Foundation Cracks: An Essential Guide to Prevention, Inspection, and Repair

In my experience as a professional home inspector, I've noticed a common theme in many houses: cracks in concrete slabs and foundation walls. This is a normal part of the life cycle of concrete, which shrinks as it cures, a process that's more about chemistry than drying. If you've ever set foot in a house, chances are you've come across hairline cracks in the garage floor, basement, or even on patios. These cracks are typically due to the natural expansion and contraction of concrete as it settles. You, as a homeowner, should periodically measure the length and width of cracks to best determine whether a larger issue exists. Home inspectors can only measure the crack length found at a fraction of the time necessary to detect growth – usually between 2-3 hours.

A practical tip I often give is to photograph these cracks. This way, you can compare their progression over time. Most of these hairline cracks develop slowly as a house settles, or due to changes in the soil moisture content around your home. Even shifts in how weight is distributed inside your house can cause small cracks in walls or ceilings.

You can play a significant role in preventing foundation cracks in your home. A key measure is managing the water drainage around your home. Make sure the soil grading around the perimeter slopes away from your house and is well compacted. This helps minimize water accumulation near the foundation, which can cause damp basements and freeze-thaw damage. Pay attention to your gutters too – they should be clear of debris and the downspouts should ideally extend 4 to 6 feet away from your foundation.

When inspecting your home's foundation, look out for bulges or leaning in the foundation walls. These signs often indicate movement beyond normal settling. Cracks wider than a quarter inch, or cracks that are uneven across their length, can also be red flags. A thorough foundation inspection involves checking both inside and outside the house.

Inside the house, look for signs like floor joists not sitting right, doors or windows that are stuck, support columns out of alignment, or an unusual number of drywall cracks. In older homes, it's common to find floors that lean or pitch, reflecting the building standards of the time. Checking the basement and attic can reveal issues with the home's structure, like damaged roof trusses.

Cracks in floor tiles can be due to foundation issues, though sometimes they're just the result of poor installation. Similarly, masonry cracks around windows or doors could indicate more than just normal settlement. It's important to seal these cracks and maintain the masonry to prevent water damage and other issues. Excess cracks in vinyl or ceramic tiles are also indicative of faulty floor installation or foundational freezing issues below.

What Causes a Foundation to Crack

1) Soil movement below the home

Soils with high clay content are particularly susceptible to changes in moisture. When these soils get wet, they can expand considerably. Conversely, during dry periods, they contract. This cyclical process of expansion and contraction can cause the soil to shift unevenly, leading to the movement of the foundation, known as heaving and settling. Over time, this can result in cracks and structural damage to the foundation.

Additionally, water flow from heavy rains, flooding, or poor drainage can wash away the soil underneath a foundation, creating voids or uneven support. As the soil erodes, the foundation may sink or settle into the ground unevenly, a process known as differential settlement. This can lead to tilting or cracking of the foundation and, subsequently, the structure above.

2) Lateral movement of ground into foundation wall

Natural earth movements driven by seismic activity can create immediate and severe damage to foundations, pushing the earth into the home’s infrastructure. For those living close to fault lines or in earthquake-prone areas, I recommend using steel reinforced concrete or deep foundation to protect against both gradual and sudden seismic activity.

Additionally, increased hydrostatic pressure due to waterlogged soil can cause bowing or cracking in the foundation walls. It is imperative your home’s drainage system is properly installed and pitched to prevent waterlogging. Also consider obtaining a Sewer Scope Inspection with WIN to ensure your home’s plumbing system is operating smoothly, and any cracks or tree root intrusions are identified for mitigation.

3) Home weight given improper foundation stability

When a home is remodeled or expanded, the additional weight may exceed the original design limits of the foundation beneath. Poor construction won’t account for this variable, and homes built using substandard materials don’t provide the necessary support. It is imperative you obtain a One-Year Warranty Inspection to ensure the original builders didn’t create lasting and expensive damage to your home’s foundation upon build. WIN’s One-Year Warranty Inspection gives you the assurance you need to move forward knowing you have your money’s worth on your greatest investment. A new build typically takes around a year to settle, making the one year mark a perfect time to ensure construction ran smoothly and your home is safe to live in for years to come.

Inadequate footings are essential to the home’s foundation, spreading the home’s load across the soil. If they are not wide enough or deep enough to distribute the home’s weight or were constructed without proper reinforcement, the stability of the home’s foundation can be compromised.

Foundation cracks can also occur when tree roots grow into and push against the structure, typically caused by their proximity to the home. Roots also absorb a significant amount of water from the soil, causing the soil to shrink away from the foundation and crack the settlement.

Extreme temperature changes as a result of climate-related shifts over the past 50 years. Thermal expansion and contraction places an enormous amount of stress on the structure of a home. Watch for frost heaving in colder climates, which involves the freezing and thawing of ground that can cause the soil to expand and lift, exerting upward pressure on the foundation. If you’re living in a population-dense area, be weary of nearby construction – excess vibrations from traffic and construction an cause movements in the foundation, resulting in cracking. Consult your nearby city office to review city ordinance violations regarding construction impingement on your home.

Floor joists are another essential part of your home’s infrastructure, resting atop metal or wooden beams. Common issues with floor joists include misalignment with beams and floors, creating a slant indoors, window or door opening and closing problems, and tilted support columns. Homes older than 75 years typically have pitched floors that lean towards the center of the home, as outdated building standards create issues today.

While home inspectors play a crucial role in identifying potential foundation issues, we are not typically licensed structural engineers. In cases of significant settlement or movement, you should consult a licensed structural engineer or a qualified foundation expert for a comprehensive evaluation.

Of course, when consulting a home inspector, it is important you understand what type of home foundation you have to ensure they are equipped with the right tools upon arrival. If you do not know your home’s foundation type, inform your WIN home inspector.

In the United States, homes are built on various types of foundations, each designed to suit specific geographic conditions, climate, and construction methods. Here’s an overview of the most common types of home foundations you’ll find across the country.

1. Slab Foundations: Slab foundations are a single layer of concrete, several inches thick, poured directly onto the ground. They are reinforced with steel rods known as rebar. Slab foundations are prevalent in warmer climates where the ground does not freeze and cause the foundation to crack. They are cost-effective and quick to construct but do not offer an under-home space that can be used for storage or utilities.

2. Crawl Space Foundations: Crawl space foundations elevate a house approximately 1-to-4 feet off the ground. They are typically built using cinder blocks to create a perimeter wall that supports the home’s structure. This type of foundation is common in areas where dampness and termite damage are concerns because it allows air circulation under the home. However, they require proper ventilation to prevent moisture accumulation, which can lead to mold and wood rot.

3. Basement Foundations: Homes in colder climates often have basement foundations, which consist of a deep hole – typically at least 8 feet – with poured concrete walls forming the foundation. Basements can be finished to create additional living space or left unfinished for storage and utilities. They provide excellent shelter from extreme weather and can add significant square footage to a home. However, basements can be prone to dampness and require waterproofing measures.

4. Pier and Beam Foundations: Similar to crawl spaces, pier and beam foundations consist of piers or columns that support beams or floor joists which, in turn, support the house. This foundation type allows easy access to utilities and provides protection from soil shift. It's especially suitable for regions with expansive clay soils. Pier and beam foundations are also easier to repair than slab foundations since the space beneath the house is accessible.

5. Pile Foundations: Pile foundations are used in constructions where the soil is too weak to support a traditional foundation. Long, cylindrical columns of wood, steel, or concrete are driven into the ground to transfer the load of the structure to stable soil or rock found deep below the surface. Pile foundations are common in coastal areas and places with high water tables.

6. T-shaped Foundations: A T-shaped foundation is a traditional method for supporting structures in areas where the ground freezes. The footing is placed below the frost line, and the walls are constructed and poured on top of it. This type provides extra stability in fluctuating temperatures and is excellent for supporting heavier loads, such as a house with a full basement.

7. Frost Protected: These foundations are specifically designed for heated buildings in cold regions. They incorporate special insulation techniques, reducing frost penetration under the building and thus the likelihood of freezing-induced damage.

8. Raft or Mat Foundations: Raft foundations are used where soil conditions are especially poor or the structure’s load is unevenly distributed. A thick, reinforced concrete slab extends across the entire footprint of the building, distributing the weight over a large area.

Each type of foundation has its benefits and drawbacks, and the choice of which to use depends on the local environment, soil and weather conditions, and the specific needs of the building. It’s essential for homeowners to understand the type of foundation their home has, as it affects everything from the home's stability and durability to potential maintenance issues and insulation properties.

Foundation cracks, while common, should not be overlooked. Regular monitoring, preventive maintenance, and proper drainage are key in mitigating potential damage. In cases of significant cracks or other signs of foundation issues, you should consult a professional to ensure the structural integrity of your home.