When you spot a crack running through your driveway, patio, or garage, questions like “Did something go wrong?” “Should I repair this?” or “Is it going to get worse?” quickly start spinning through your mind.
At Roe Painting, we’ve seen every kind of concrete crack you can imagine on residential patios, driveways, commercial warehouse floors, and pool decks across Idaho and Nevada. And here’s the truth: some cracks are totally normal. Others? Not so much. Knowing the difference is what protects your concrete and your budget.
In this article, we’ll break down why concrete cracks, which cracks are worth worrying about, and how to protect your concrete from future damage, whether it’s brand new or 20 years old.
We'll cover:
- Why Does Concrete Crack?
- When to Worry About Concrete Cracks
- What Makes Cracks Worse
- How to Protect Your Concrete Before and After Cracking Starts
Why Does Concrete Crack?
In short, concrete is strong, but not flexible. It’s built to handle heavy loads, but when it moves, shrinks, or dries unevenly, it often cracks.
Here are the most common reasons why your concrete is cracking:
1. Shrinkage During Curing
Concrete naturally shrinks as it cures. The surface can develop hairline cracks if the mix dries too fast or isn’t properly controlled. These are usually cosmetic, but they’re incredibly common—even in brand-new slabs.
2. Temperature Changes (Especially Freeze-Thaw Cycles)
Concrete expands in the heat and contracts in the cold. In places like Boise and Elko, this daily and seasonal cycle is especially harsh, and one of the most common reasons our customers are looking for concrete coatings or concrete restoration. When moisture seeps into the surface and freezes, it expands, widening even the smallest cracks.
3. Lack of Proper Control Joints
Control joints are intentional grooves that give concrete a place to crack in a straight, clean line. When joints are missing or poorly placed, cracks often form in random or more visible areas instead.
4. Poor Soil Prep or Subgrade Compaction
If the ground beneath the concrete isn’t compacted properly, it can settle unevenly. That shift in the foundation puts stress on the slab, often resulting in long, uneven cracks. This is a leading cause of exterior slab damage.
5. Overloading the Surface
Concrete is strong, but not invincible. Concentrated loads from parked trailers, forklifts, or even decorative items like planters can exceed its strength, especially if it’s already compromised by age or weathering.
6. Corrosion of Rebar or Embedded Steel
When moisture gets deep enough to reach the reinforcing steel inside concrete, the metal can rust and expand. This internal pressure pushes outward and causes cracking, especially in older or poorly sealed slabs.
Bottom line? Concrete cracking is common, but understanding the “why” helps you know when to act and how to prevent further damage.
When to Worry About a Crack in Your Concrete
Most concrete cracks are harmless. But some are red flags, and knowing which can save you from more serious damage and repair costs down the line.
It’s Wide or Getting Wider
- Hairline cracks (<⅛”) are common and usually cosmetic
- Wider cracks (>⅛” or more) could signal movement, poor base prep, or structural stress.
Tip: Mark the end of a crack with a pencil and check back in a few weeks. If it’s growing, it needs professional evaluation.
It Runs Across the Slab, Not Along a Joint
Control joints are there to crack, so if cracking appears outside of joint lines, especially in a pattern or radiating from corners, it may point to underlying issues like soil movement or stress failure.
It’s Accompanied by Flaking or Spalling
If the surface of the concrete is breaking apart or crumbling, that’s more than just a crack. It often indicates moisture intrusion or freeze-thaw damage starting to degrade the slab.
You See Rust Staining or Moisture Near the Crack
This may suggest that water has reached the internal steel reinforcement, leading to corrosion and expansion from within, which can cause more severe cracking.
It’s Creating a Safety Issue
Any crack that creates a trip hazard, collects standing water, or continues to widen across walkways, entries, or workspaces should be addressed for liability reasons, even if it’s not structural.
Rule of Thumb: If a crack affects safety, drainage, or continues to grow, it’s worth looking at. You don’t have to wait until it’s “bad enough” to act.
Spalling or Flaking Concrete That Can Be Repaired With Concrete Coatings
What Makes Cracks Worse Over Time
A small crack today can turn into a big problem tomorrow, but only under certain conditions. Left untreated, several common factors can accelerate damage:
- Water Intrusion: Moisture is the #1 enemy of concrete. When it seeps into cracks, it weakens the substrate and invites freeze-thaw damage, especially in northern climates.
- Freeze-Thaw Cycles: In colder months, any water inside a crack can freeze and expand. That expansion widens the crack, creating a cycle of worsening damage year after year.
- De-Icing Salts and Chemicals: Used to clear icy walkways quickly, these materials can degrade concrete over time, especially if cracks are open and unsealed. They also promote corrosion of rebar in reinforced slabs.
- UV Exposure and Surface Degradation: Sunlight slowly breaks down the top layer of untreated concrete, making the surface more porous and allowing water and debris to penetrate faster and deeper.
- Ignored or Improper Repairs: Filling a crack with the wrong product–or ignoring it completely–can trap moisture, fail under stress, or even cause bonding issues for future coatings or resurfacing.
The longer cracks are exposed, the more likely they are to expand, absorb water, and accelerate wear. Protecting concrete early is almost always cheaper than repairing it later.
How to Protect Concrete Before and After Cracking Happens
You can’t always stop cracks from forming, but you can stop them from spreading, deepening, or causing bigger issues down the road.
Whether it's newly poured or 10 years old, here are five smart ways to protect your concrete:
1. Apply a Penetrating Sealer
Penetrating sealers soak into the concrete surface and form a barrier that helps repel moisture and de-icing chemicals. They’re nearly invisible and ideal for driveways, sidewalks, and patios where you want to preserve the natural look of concrete.
2. Use a Topical Coating for Extra Protection
Topical coatings, like polyaspartic or epoxy systems, sit on top of the surface to create a durable layer that’s UV-resistant, waterproof, and customizable in color or texture. Great for garages, pool decks, and commercial spaces.
3. Maintain Control Joints and Expansion Gaps
Joints help manage natural movement in concrete. Keeping them clean and sealed helps prevent random cracking and water intrusion.
4. Schedule Seasonal Cleanings and Inspections
Dirt, salts, and freeze-thaw cycles are rough on concrete, especially in our Boise and Elko climates. Regular cleanings and checkups help catch issues early and extend the life of your surfaces.
Pro tip: Whether your concrete is new or already cracking, the right protection plan can save you years of wear and thousands in repairs.
Thin Cracking in a New Concrete Slab. Patched and Concrete Coating Can Be Easily Applied Over It.
When Coatings Won’t Help
While sealers and coatings can protect against moisture, surface wear, and UV damage, they won’t stop structural cracking caused by deeper issues. If your concrete is cracking due to tree root intrusion, poor subgrade prep, improper rebar placement, or ongoing foundation movement, surface protection alone won’t solve the problem.
In these cases, it’s best to consult a concrete repair specialist or structural engineer before applying any coating system.
Some Concrete Cracking is Normal, But Watch for Red Flags
Now that you know why concrete cracks, when to worry, and what makes damage worse, you know how to successfully protect your property and avoid costly repairs.
From harsh winters to heavy use, your concrete is exposed to real stress every season. Even small cracks can let in moisture and create bigger problems over time if left untreated.
Whether you’re maintaining a driveway, a warehouse floor, or a commercial patio, it’s worth taking a proactive approach. A professional-grade sealer or coating can keep your concrete in better shape for longer.
At Roe Painting, we help homeowners and property managers across Idaho and Nevada protect their concrete with long-lasting sealers and coatings. If you’re unsure what your surface needs are, we’re happy to take a look and recommend a plan that fits your space and your budget.
To learn more about concrete coatings and how they can protect and enhance the strength of your concrete, read The Ultimate Guide to Concrete Coatings. In it, we discuss coating types and their unique benefits.
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