A crack in the wall might spell big problems in your foundation
Any cracks that are wider than 1/8 inch or are raised on one side could indicate structural damage.
Horizontal or stair-step cracks on foundation walls require immediate attention from a foundation repair company.
Cracks that leak water may need stabilization alongside basement waterproofing services.
Knowing what foundation cracks are normal and which indicate signs of foundation issues can give you peace of mind and save you money and lost sleep. For example, hairline cracks are not unusual as foundations expand, contract, and settle over time. However, if a crack seems to be getting larger, there might be a deeper issue.
In this guide, we’ll explain everything you need to know about different foundation cracks, when to worry, and when to hire a foundation repair contractor.
There are many things that can cause foundation cracks to form, some of which can lead to structural damage. Understanding the underlying cause of the crack can help you determine if you have a bigger issue on your hands.
Normal settling: Normal settlement of the foundation into the soil is the most common cause of foundation cracks. As the concrete and the structure above adapt to and causes changes in the soil, you’ll see hairline cracks forming on the walls and the slab. Provided they are less than 1/8 inch wide and aren’t leaking water during rainfall, you likely don’t need to worry about basement floor cracks, slab cracks, or settling cracks on your foundation walls.
Building on soil that wasn’t compacted well enough: Contractors should always build foundations on undisturbed soil, but in nearly all cases, your homebuilder will need to excavate to install footings to build a crawl space or basement. When the soil on the site isn’t compacted properly before construction begins, it’ll continue to settle over time and cause anything built on it to shift. This can lead to differential settlement, which is when a portion of your foundation moves more than the rest, often leading to structural cracks.
Freeze-thaw cycles: The expansion and contraction of the soil freezing and thawing moves against the foundation, putting pressure on the walls and slab that can cause cracks. Building code mandates that all modern foundations have footings that extend at least a foot under the frost line to avoid this issue, but the portions of the foundation above are still subject to movement.
Poor drainage: Poor drainage allows water to soak into the soil around the foundation. In areas with clayey soil, especially, the soil will expand in response to moisture, creating hydrostatic pressure, which is added pressure created by wet, expanding soil against the foundation walls. Over time, the foundation will crack in response to the added pressure, likely leaving you with structural damage.
Sinkholes: Sinkholes are voids created underground, often as a result of runoff soaking down to bedrock and gradually dissolving it. Eventually, the soil above will cave in, leaving a portion of any foundation above without support. Sinkholes are typically only an issue in areas with karst landscape, where the bedrock is made of limestone or dolomite.
Natural disasters: Natural disasters like earthquakes and floods can cause foundation cracks, either from suddenly shifting soil or saturation that creates excess hydrostatic pressure.
Being able to tell the difference between harmless cracks from normal settling and those that indicate structural damage is crucial for self-diagnosing your foundation damage. Below, we’ll cover all of the cracks that could suggest a serious problem.
Hairline cracks under 1/18 inches are normal, but if you spot larger or deeper cracks, call a pro immediately. Cracks exceeding 1/4 inches are a sign of more serious structural damage and should be handled by a foundation pro.
Horizontal foundation cracks on the concrete block wall in your basement or crawl space often indicate severe structural damage. Freeze-thaw cycles or hydrostatic pressure usually cause these cracks. Eventually, these cracks can cause walls to buckle inward, in which case the structure above can lose support from your foundation.
In extreme cases, this kind of issue could cause total structure collapse. In less severe cases, it can lead to interior damage to your drywall and other building materials, and it can allow water into your foundation.
Cinder block foundation walls might have cracking in a stair-step pattern along the mortar joints. These cracks can indicate differential settlement, which is when a portion of your foundation sinks into the ground more quickly than the rest of it. It can mean major problems for the structural integrity of your foundation and requires help from a professional.
Any foundation cracks, whether they’re on your foundation wall or slab, require sealing to keep water out of your home, but this is especially true for cracks that are wider than 1/8 inch. These are more likely to let water and water vapor in, which can lead to increased humidity, mold growth, and pest infestation.
Cracks that are wider than 1/8 inch require professional attention. If they are even across the gap, they might just be unusually large settlement cracks, but they could suggest budding structural issues. If one side of the concrete pushes out more or sinks below the other, you could have differential settlement under your home, which almost always indicates a structural problem.
Cracks that continue to expand over time can also suggest problems with the support under your home. Monitor all cracks by marking the length with a pencil and checking every couple of months to make sure the crack isn’t growing.
If the concrete around the crack looks or feels damp after rainfall or you see water around the crack, you may have a water infiltration issue. This can occur regardless of the type of crack, the underlying issue, and how wide the crack is, so you should routinely inspect all cracks to monitor for water intrusion.
If water or moisture coming through the crack is the only issue, it’s possible to do some DIY foundation crack repair, but we recommend calling in a professional to ensure the work is done properly and to address any underlying problems, like poor drainage outside.
If one side of the crack is pushed in so the concrete is not flush or even on both sides of the crack, that indicates that there’s movement. You should contact a professional to inspect the foundation immediately. This could be a result of hydrostatic pressure if the crack appears on your foundation wall or differential settlement if it appears on your slab.
Even a very thin crack that looks like it’s from normal settlement can be an issue. If the cement blocks or concrete is chipping on either side of the crack, it could mean that you have an unidentified water intrusion problem. This type of flaking is called concrete spalling, and it usually results from moisture or water wicking or seeping through the concrete and weakening it from the inside.
If you’re unable to find evidence of water coming in during rainfall, spalling can help identify a moisture issue related to your foundation crack.
One hairline crack is not an immediate cause for alarm, but if you see two, three, or more cracks grouped together, there’s possibly something more problematic going on. The worst-case scenario would be multiple hairline cracks on your slab that form in a circular pattern. This is often a result of frost heave, which is when the moisture in the soil below freezes and puts upward pressure on the concrete.
As we’ve discussed, some foundation cracks are normal and nothing to worry about until you see some particular warning signs that something more destructive is happening to the structural integrity of your foundation. Non-structural cracks happen when materials like concrete and masonry naturally shrink while drying out and curing, as well as when the concrete settles into the surrounding soil. These kinds of cracks are usually very thin hairline cracks, less than 1/8 inch across the gap, and they don’t grow over time.
You should always take care to patch hairline cracks with an epoxy sealant. If your home is less than two years old, your warranty may cover the repair costs—but don’t forget to take photos of the crack to submit with your claim.
Although non-structural cracks don’t pose an immediate threat to the structural integrity of the foundation, they can allow water and moisture to work their way into your home, which can, in turn, lead to issues with poor indoor air quality, greater wear on your heating and cooling systems, pest infestation, mold growth, and damage to your building materials.
You can take precautions to prevent cracks from appearing in your foundation, such as the following:
Keep your gutters in good shape. If you don’t have gutters, downspouts, and downspout extenders installed, installing them is one of the best things you can do to improve drainage and avoid foundation cracks from saturated soil. Make sure to keep them clean and free of leaks.
Grade your soil. Slope the soil away from the house so water does not sit against the foundation walls. The gradation will naturally pull runoff away from your foundation, reducing the risk of it interacting with the concrete and the surrounding soil.
Install a French drain. A French drain is an underground foundation drainage system that collects runoff from the soil and reroutes it to an area safe for disposal. This can help prevent hydrostatic pressure against your foundation and limit water intrusion through the concrete.
Address issues early. Foundation problems will almost always worsen over time, so addressing minor issues early will save you money and frustration and can prevent small cracks from turning into structural damage. Carry out a DIY foundation inspection annually and call in a professional at the first sign of a problem.
Foundation repair costs around $5,000, on average, and while it might be tempting to try to DIY a solution to save on labor costs, it’s often not a good idea. Foundation issues are complicated to diagnose properly, and carrying out the actual repairs can actually end up doing more damage to your home or making your issue worse. Call in a professional if the cracks you’re experiencing meet any of the criteria outlined above.
If you’re just dealing with settling cracks that are 1/8 inch wide or less, aren’t expanding, and haven’t shown any signs of letting water or moisture in, you could seal those yourself using an epoxy concrete crack sealant. Beyond that, though, your best bet is to hire a structural engineer or a foundation repair company near you to inspect the issue and implement a permanent solution.
Foundation cracks that are 1/8 inch wide or less, aren’t uneven across the gap, and don’t continue widening over time are usually just normal settling cracks and don’t suggest structural issues. Horizontal cracks and stair-step cracks on foundation walls, any cracks that continue widening, are wider than 1/8 inch, or where one side juts out beyond the other, are often indicative of structural damage.
Yes, you can live with a cracked foundation—in fact, most people do. Virtually all foundations crack from normal settlement, and while settling cracks benefit from sealing to prevent water and moisture intrusion, most aren’t an issue. If you have structural cracks in your foundation, it might be safe to live in your home for some time, but you should address them immediately to prevent structure collapse and major property damage.
Homeowner’s insurance doesn’t cover foundation cracks unless they’re a result of a natural disaster like an earthquake, vandalism, or a vehicle accident that causes sudden damage. Taking care of your foundation to prevent problems with expansive soil and drainage is considered ongoing maintenance, and your insurance company expects the homeowner to carry out that preventative maintenance.
