Causes of Concrete or Block Foundation Cracks and How to Save Your Home

Reviewed by Matt DiBara
Updated January 28, 2022
A house at sunset
Photo: Ivan / Adobe Stock

Knowing when and how to repair cracks in your foundation can protect your home—and your peace of mind

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When you start noticing cracks creeping across your home’s concrete block foundation, it can be pretty scary. The good news: Not all cracks spell trouble for your home’s structural foundations, but they are certainly something to be cautious of.

Many cracks are cosmetic, the result of ordinary weathering and aging of your concrete or block foundation. After all, it’s not easy to hold a whole house up in all kinds of weather conditions. (You’d look a bit worse for wear after a while too!)

When a Crack Is More than Cosmetic

Even when cracks indicate a bigger issue with your home’s foundation, that doesn’t mean it’s time to panic. Repairs can be made, and while they may not come cheap, they don’t have to cost an arm and a leg either. Even major foundation cracks can generally be repaired for around $800, on average.

But those costs can climb if there are other, more significant issues with your soil, drainage, or how it was designed or installed. These issues can require additional digging or installing supporting piers around the foundation. 

In almost all cases, though, it’s a good idea to consult with a structural engineer to help you figure out if the cracking is something you need to address, as well as the safest and most cost-effective way to protect the structural integrity of your home.

What to Look For

One of the most important tell-tale signs that the cracks in your concrete block foundation may be more than cosmetic is if they’re horizontal, large, and growing. Make sure to closely monitor even small cracks for changes, noting whether they are lengthening or widening and how quickly. You should also pay attention to things like temperature and rain exposure because these details can help the experts determine what’s causing the cracks and how best to repair and prevent them.

"One simple way to keep an eye on this is the quarter test," says mason and general contractor Matt DiBara. "If you can fit a quarter within the crack, it is important to keep track of its movement. One approach is to check it every six months using a quarter to guage whether the crack is changing."

According to DiBara, this test is helpful in distinguishing between something minor, like a natural expansion crack of little worry, and something major like a section of insufficient drainage or soil.

If you do notice changes, you’ll need to call in a professional foundation repair company near you. Having a record of all these details can help your pro more quickly diagnose the problem and come up with the best solution for your home—and your bank account.

How Foundation Cracks Happen

Lots of factors, from soil conditions to weather events to plant and tree growth, can impact your home’s foundation.

1. Unbalanced Soil Pressure

Unbalanced soil pressure is the most common culprit for horizontal cracks in your concrete blocks. When soil pressure becomes excessive, it causes the foundation to shift. The movement generally causes horizontal cracks at the center or near the top of the wall. Sometimes, the soil pressure may shear the first course of concrete block above the basement floor slab, causing the wall to slide inward. These cracks will staircase up and down the foundation walls near the ends of the wall.

2. Poor Drainage

Horizontal cracks often occur in areas with not-so-great drainage. If the soil beneath and around your foundation becomes oversaturated, this causes the soil to gradually erode away and creates pressure imbalances, causing your blocks to crack.

3. Weak and Vulnerable Areas in Foundation Walls

Cacks can also be found in porches or steps anchored to the foundation walls. When porches or steps are installed, they typically have a very shallow foundation and may settle due to the un-compacted fill soil along the foundation, causing the top of the wall to pull outward or push inward.

4. Other Potential Causes

Less common causes of horizontal cracks include soil settlement, landslides, or the lack of foundation anchors connecting the wall to the floor framing.

What to Do About Horizontal Cracks

There are few things scarier to a homeowner than a faulty foundation. But you have a number of options for repairing cracks in your foundation.

1. Install Steel Support

If the wall is pushed inward due to unbalanced soil pressure, installing steel columns or steel reinforcing rods with solid filled concrete blocks will help brace the foundation. If the house is located on a sloping lot, the appropriate repair may also include reinforced concrete buttresses or counterforts.

2. Carbon Fiber Straps

Some homeowners prefer to use carbon fiber straps to stabilize and reinforce their concrete foundation. Generally, the straps are affixed to foundation walls using epoxy, but this often costs more than bracing with steel columns or reinforcing walls. Carbon fiber straps also will not fully repair a wall that is sheared at the bottom.

3. Yard Anchors

Yard anchors can also help to provide support to a cracking foundation. They can consist of straight stakes or spiral steel to help decrease erosion and provide structural support, particularly by preventing the soll pressure imbalances that are so damaging to your foundation.  But these require tightening twice a year due to anchor creep in the soil, and they also cost more than bracing.

4. Install a New Wall

Another possible repair is to excavate the foundation’s and install a new exterior wall against the existing one. But unless this new wall is specifically designed as a self-supporting retaining wall for your home, this method might not stop lateral movement. 

5. Regrade Your Yard

While you might think you’re all set once you’ve installed your reinforcing rodes or built a new exterior wall, think again. Regrading the yard to better level the soil, stop erosion, and prevent moisture from accumulating around your foundation may, in fact, be your best solution. 

But to get the most bang for buck following regrading, you’ll still need to pay particular attention to your guttering and drainage to prevent the problem from rearing its ugly head again. Though, installing an exterior or interior waterproofing system does not eliminate soil pressure or stop lateral movement.

6. Go Pro

When you find yourself facing foundation repairs, one of the best things you can do for yourself and your home is to bring an expert on board. A local structural engineer will have the training and expertise to pinpoint the cause of the issue. They will also analyze the layout of the lot and environmental conditions in your area. This will allow them to devise the most efficient, effective, and affordable repair strategy for your needs.

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