when are slab cracks bad?

When Are Slab Foundation Cracks Bad and How Can You Tell?

You’re looking at your house (or a house to buy) and see some cracks in the slab foundation. These could be cracks on the flat horizontal surface of the slab or cracks on the outer perimeter of the home. You’re wondering if any of these slab cracks are “bad” or something to be concerned about. 

Anchor Foundation Repair Bryan College Station

How can you tell the difference between a “normal” slab crack and a crack to worry about?

At Anchor Foundation Repair, identifying foundation problems is what we do. Over the last 35+ years in business, we’re more than qualified to explain the difference between slab cracks that don’t pose a problem vs. cracks that indicate foundation settlement or developing issues.

This article will describe and explain what kinds of slab cracks are indicators of foundation settlement and problems. We will also discuss what to do about any cracks you find and the next steps to take in handling this issue.

What Is Considered “Normal” in the Slab Crack Department?

This is a *hard* fact right here: concrete cracks and sometimes it’s normal. Super thin hairline cracks happen often when concrete is curing and drying. These hairline cracks typically appear most frequently on flat horizontal surfaces like an exposed slab foundation.

You might see one or many hairline cracks running across the top of a slab surface when the carpet is removed inside a home or in a garage where the concrete is always exposed. These hairline cracks can span long or short distances or anywhere in between.

hairline cracks

The key here is that the cracks have no thickness to them. They are called hairline cracks because they are very thin like a strand of hair. These cracks are also called “shrinkage cracks” and they appear during the curing process. 

Sometimes the cure happens too quickly due to (our delightful Texas) heat or there’s too much water in the concrete that evaporates. Hairline cracks can also appear when the perimeter form boards are improperly supported. 

Some concrete cracking is considered normal because we know that all concrete cracks at some point, but the cracks don’t indicate a foundation or structural failure in all cases. . .

Can Hairline Cracks Be Prevented in a New Slab?

There are some preventative measures that can be taken to avoid concrete cracking like microfiber and additives incorporated into the concrete mix. Covering and hydrating a slab after it is poured can slow down the curing process to minimize shrinkage cracking as well.

weather creates foundation problems

Even if a concrete company uses all the good ideas and best practices, there are many environmental and construction factors they are attempting to control during slab pour. It’s difficult to achieve 100% perfection even if you’re trying. 

Plus, not every construction company takes every prevention effort. Ultimately, they know that these kinds of cracks are cosmetic and don’t impact structural integrity. 

What about Cracks in the Perimeter Beam of the Foundation?

which slab cracks are bad?

Cracks that you might see on the exterior of the home when looking near the ground are different than the ones you see running across a horizontal surface as described above. 

Sometimes cracks in a perimeter beam are cosmetic, harmless, and/or just look kinda ugly. Sometimes perimeter beam cracking can be an indicator of foundation settlement, though it’s not the strongest sign.

Cracks in perimeter beams mean different things depending on the direction they are running and where they appear. We’ve segmented the different types of cracks below.

Horizontal Cracks in a Concrete Perimeter Beam

If you see horizontal cracking along the perimeter beam running parallel to the ground, you might be alarmed. It looks like something severe is going on, but it’s not necessarily a structural integrity issue. This kind of cracking is related to concrete ingredient ratios, weather conditions at the time of construction, or improper placement of rebar within the beam. 

bad slab cracks?

Horizontal cracks in a concrete perimeter beam are a sign of poor workmanship or poor installation conditions but an unlikely sign of foundation failure. I wouldn’t go so far as to say it’s normal, but it has been known to happen.

Vertical or Diagonal Cracks in a Concrete Perimeter Beam

Vertical or diagonal cracking can sometimes indicate foundation settlement. However, other signs and symptoms of foundation problems would have to be present for this to be a concern. If there are no other signs around the home, then it’s likely just a cosmetic imperfection.

Cracks on the Corners aka Corner Pop

Corner pop looks very concerning like the corner of your home has come off. This condition happens on brick homes because brick expands at a different rate than concrete when exposed to heat. Most often corner pop is a workmanship issue due to non-existent, imperfect, or faulty separation between the brick masonry work and the concrete. 

corner pop examples

You should not be overly concerned about foundation issues with corner pop, but you may want to get it cosmetically repaired. We’ve got a whole article with a lot more detail on corner pop for you if you need it.

What Kind of Slab Cracks Should I Be Concerned About and Why?

We’ve gone over a bunch of different kinds of cracks, and most of them are ones to not be particularly concerned about. But are there any that you should be more worried about? 

If you have a crack running through the surface of your slab that is rather wide, displaced with one side being higher than the other, or clearly separating over time, you should take note. Vertical and diagonal cracks on the perimeter beam should also be observed throughout the year and monitored. 

is this a bad slab crack?

If a crack is actually pulling apart and getting wider, then these cracks are more concerning.

But if we’re being really honest here, any concrete slab cracking is not the best indicator that you have foundation problems. I feel like I should say this twice (or maybe you can just silently repeat it to yourself right now).

The top signs of foundation settlement and problems are found on vertical finish surfaces, like diagonal drywall cracks, trim separations inside and outside the home, and exterior brick. Other top signs of foundation settlement are related to home functions like door problems and plumbing drain line issues.

So if you’re really trying to figure out if there are foundation problems with this home, don’t look to the slab. Look elsewhere for more reliable foundation settlement indicators.

What Should I Do About a Cracked Slab?

what to do about slab cracks

If you’re wondering what you should do about slab cracks, I would say in most cases not to worry about them. If you see no other signs of foundation problems, then your cracks are very likely a cosmetic issue. 

You could address the *look* of things with a surface repair, but it would mostly be to make you feel better or cover up some minor imperfections.

Repairing Slab Cracks with Sealant

People ask about sealant for slab cracks. While you certainly have the option to seal cracks, it would be a personal choice. If it makes you feel better to seal it or cover up the imperfection, then feel free to do so. But again, it would just be to help you feel better.

home foundation repair

We are not proponents of sealant. It seems like a waste of time and effort because it doesn’t really solve anything. We don’t offer it as one of our services, but you could probably find someone out there to take your money and have it done. But don’t feel like this is a required action, because it’s not.

Repairing Your Slab with Foundation Problems

can I get my foundation repaired?

If you have slab cracks and also other signs and symptoms of foundation settlement that are bothering you, then it might be time to consider foundation repair. 

How much are the signs of foundation issues stressing you out? Is settlement making you worried or angry because something isn’t working right – like your front door? Do you feel embarrassed on don’t want to invite people over?

Knowing when the time is right for foundation repairs is often subjective because it depends in part how you feel about the issues. Check out this article for help with knowing when to move forward with getting your foundation repaired.

Preventing Slab Cracks and Foundation Settlement

Can you prevent slab cracks? Not really. Hairline cracking just happens and most likely happened before you even purchased your home. Remember that hairline cracks don’t affect structural integrity. 

Can you prevent foundation settlement? Not really either. There are ways to try for sure, but they are not guaranteed to work every time. 

slab cracks in floor

Foundation settlement is most often caused by expansive clay soil and its behavior through rainfall fluctuations over many years. It’s you and your house vs. a massive soil system and the weather: a battle you are unlikely to win against the strong forces of nature.

There’s absolutely nothing wrong with attempting to minimize your chances of foundation issues. Conscientious and responsible homeowners would want to know they did everything they could to prevent issues. Just know that it can happen anyway despite your best efforts.

Check out this article for prevention ideas: Can I Prevent Foundation Problems in My Home? 3 Ways to Try

Look for True Signs of Slab Foundation Issues

Now that you know that slab cracks are not the best indicator of foundation issues, what should you look for instead? If this is a home you own or live in, monitoring your home throughout the year is a good next step along with learning the true signs. If it’s a home you are thinking of buying, then skip straight to looking for true signs of foundation problems.

top signs of foundation problems

We understand the stress and anxiety that comes with worrisome home issues. At Anchor Foundation Repair, we offer fair and impartial assessments, empowering education, and a fully transparent repair process. After 35+ years in business, we want you to know as much about foundation repair as we do and we’ve got no secrets to hide from the Brazos Valley community.

Check out this definitive and complete resource to decode the true and confusing signs of foundation issues with the Ultimate Guide to Foundation Problems (Real + Misleading Signs).