Cracks in concrete are common, and most small ones can be repaired at home with the right tools, a bit of prep work, and the correct repair material. The basic process usually involves cleaning out the crack, widening it slightly if needed, and filling it with a suitable concrete filler or patching compound. But not every crack is a simple fix. Large, deep, or shifting cracks can point to a bigger problem underneath, and those usually need a professional to take a look before any repair is made.
This guide walks through how to spot different types of cracks, what tools and materials you need, and the exact steps to repair them. Whether you are working on a driveway, sidewalk, or patio in Phoenix, AZ, knowing the difference between a simple patch job and a job for the pros can save you time, money, and a lot of frustration. At S&S Paving & Construction, we see every kind of concrete crack, and we are here to help you figure out which ones you can safely handle yourself.
Why Does Concrete Crack?
Concrete cracks for a handful of common reasons, and understanding the cause can help you figure out the right fix. Concrete shrinks slightly as it dries and cures, and this shrinkage is one of the most common reasons small cracks form, even in newly poured concrete. Temperature changes and weather also play a role, since concrete expands in heat and contracts in cold, and repeated cycles of this over time can cause cracking.
Soil movement or settling underneath the concrete is another major cause, especially in areas where the ground shifts with moisture changes. Heavy loads and pressure, like vehicles parking on a driveway not designed for that weight, can also cause cracks to form or worsen. Finally, poor installation or drainage issues, such as water pooling near the edges of a slab, can weaken concrete over time and lead to cracking.
How to Tell What Type of Concrete Crack You Have
Not all cracks are the same, and figuring out what kind you are dealing with is the first step toward the right repair. Some cracks are purely cosmetic and easy to fix in an afternoon, while others are a sign of something happening beneath the surface that needs a closer look before you start patching anything.
Hairline Cracks
These are very thin, shallow cracks, often no wider than a strand of hair, that commonly appear on the surface of new concrete as it heals. They are usually cosmetic and not a structural concern, since they typically do not go deep into the slab. You will often see these on sidewalks, patios, or driveways within the first year, and sealing them early can help prevent water from seeping in over time.
Small Surface Cracks
Slightly wider than hairline cracks, these are still generally shallow and often caused by normal shrinkage or minor settling in the ground below. You might notice these forming in a fairly straight line or branching slightly, usually less than an eighth of an inch wide. They usually stay the same size, but sealing them helps keep water out and prevents bigger problems.
Wide or Deep Cracks
Cracks that are more than a quarter inch wide, or that appear to go deep into the slab rather than sitting just on the surface, may need more attention and a stronger repair material. These cracks are more likely to let water and debris get underneath the concrete, which can lead to further damage if left untreated. If you can fit a coin or a small object into the crack, it is a good sign that this falls into the wider category.
Cracks With Uneven or Raised Concrete
If one side of the crack is higher than the other, even by a small amount, this often points to soil movement or settling underneath the slab rather than simple surface shrinkage. This type of crack is more than a cosmetic issue, since the ground beneath the concrete has shifted enough to move one section out of alignment with the other. A simple filler will not address the movement causing it, so this type of crack usually requires more than a basic surface repair.
Structural Cracks
These cracks are usually wide, run in a jagged or diagonal pattern, and may appear in foundations, load-bearing slabs, or walls rather than just a driveway or patio surface. They can also show up alongside other warning signs, like doors or windows that no longer close properly, or cracks that seem to be spreading over time. Because these cracks can point to serious issues with the structure or the soil supporting it, they typically need a professional evaluation before any repair work begins, rather than a DIY fix.
Can All Concrete Cracks Be Repaired?
Most small, stable cracks can be repaired without much trouble. Hairline cracks and small surface cracks usually respond well to a simple filler or sealant, especially when caught early before they get bigger.
Some cracks need more attention. Wider cracks, cracks with uneven edges, or cracks that seem to be actively growing may need a stronger patching material or a more involved repair process, and in some cases, professional help.
There are also warning signs that a crack points to a bigger problem. If the crack keeps returning after repair, if it is paired with sinking or shifting concrete, or if it appears along with cracks in nearby walls or foundations, it is worth having a professional take a closer look before doing any DIY work.
Tools and Materials You Need to Fix Concrete Cracks
Having the right tools and materials on hand before you start makes the whole repair process go much smoother.
Essential Tools
- Wire brush
- Chisel or screwdriver
- Caulking gun
- Putty knife or trowel
- Safety glasses and gloves
Common Repair Materials
- Concrete crack filler
- Concrete patching compound
- Hydraulic cement
- Polyurethane or elastomeric sealant
How to Fix Cracks in Concrete Step by Step
Once you know what type of crack you are dealing with and have the right tools ready, the repair process itself follows the same basic steps for most jobs. Here is how to do it right, from start to finish.
Clean the Crack
Remove dirt, dust, loose concrete, and debris from inside and around the crack. A wire brush works well for scrubbing out the crack itself, and a shop vacuum can help clear out any remaining dust before you apply repair material. Skipping this step can cause the repair material to bond poorly with the concrete, leading to a repair that pops loose or fails early. Taking a few extra minutes here to get the crack as clean as possible sets up every step that follows for success.
Widen the Crack if Needed
For some repairs, slightly opening the crack with a chisel helps the repair material bond better, especially for thin hairline cracks where filler might not reach deep enough on its own. Widening creates a small groove that gives the product more surface area to grip onto, rather than just sitting on top of a narrow slit. This step is not always necessary though, so check your product’s instructions first, since some fillers are designed to work in thin cracks without any extra prep.
Choose the Right Concrete Repair Product
Select a filler, sealant, or patching compound based on the crack’s size, depth, and location. Thin cracks often do well with a liquid filler, while wider cracks may need a thicker patching compound that can fill more volume without shrinking as it dries. Where the crack is located matters too, since areas exposed to weather or heavy foot traffic may call for a more durable, flexible product. Taking a moment to match the product to the specific crack helps the repair last much longer.
Apply the Repair Material
Fill the crack according to the product instructions, and make sure the material reaches the deeper parts of the crack, not just the surface. Working the product in slowly, rather than rushing to fill the top, helps avoid air pockets that can weaken the repair later. Overfilling slightly is usually better than underfilling, since a gap left underneath the surface can cause the repair to crack or fail again sooner than expected.
Smooth and Level the Repair
Use a trowel or putty knife to smooth the surface and blend the repair with the surrounding concrete, so it sits flush and does not create a tripping hazard. Working in one direction with light, even pressure usually gives the cleanest finish. A smooth, level result also helps the repair blend in visually, so it looks less like a patch and more like part of the original surface.
Allow the Repair to Cure
Give the repair enough time to dry and cure before walking or driving over the area. Curing times vary by product, so always check the label for specific guidance rather than guessing based on how the surface looks or feels. Avoid rushing this step, since walking or placing weight on the repair too soon can weaken it before it has fully set, undoing much of the work from the steps before it.
How to Repair Different Types of Concrete Cracks
Different types of concrete cracks call for slightly different approaches. Hairline cracks respond well to a thin crack filler or sealant applied directly into the crack, without needing any widening first, while small surface cracks may need a light widening before applying a patching compound or filler, smoothed level with the surrounding surface.
Larger cracks or spots where concrete has broken away need a patching compound built for bigger repairs, often applied in layers if the damage runs deep. Slab cracks, especially ones with any moisture nearby, tend to do best with hydraulic cement, since it can set even in damp conditions. Polyurethane sealant works best for driveways, patios, and sidewalks because it stays flexible and lasts longer.
What Is the Best Product for Filling Concrete Cracks?
Choosing the right product comes down to matching it to your specific crack. Concrete crack filler works best for hairline cracks and small surface cracks, since it is easy to apply and holds up well for cosmetic repairs. Concrete patch is a better choice for small to medium cracks and chipped areas, offering more strength than basic filler for spots that see some foot traffic.
Polyurethane sealant is the top pick for driveways, patios, and areas exposed to weather and temperature swings, since it stays flexible and moves with the concrete instead of cracking again. Hydraulic cement works best when moisture is present or water is actively getting into the crack, since it sets quickly and bonds even in wet conditions. In general, smaller and drier cracks do fine with basic filler, while larger, flexible, or moisture-prone cracks need a stronger, more specialized product.
When Should You Not Repair a Concrete Crack Yourself?
Some cracks are better left to a professional. Consider calling for an inspection if:
- The crack is wide or appears to be growing over time
- One side of the concrete is noticeably higher than the other
- The crack runs through the foundation
- There are multiple large cracks across the same area
- Water is actively entering through the crack
- The concrete is sinking or shifting
Any of these signs can point to a deeper issue with the soil, drainage, or structure underneath, and a simple surface repair will not fix the root cause.
How to Prevent Concrete Cracks From Getting Worse
A few simple habits can help keep small cracks from turning into bigger problems.
Sealing cracks early, as soon as you notice them, helps keep water and debris out, which slows down further damage. Improving drainage around concrete, so water flows away instead of pooling near slabs, can prevent a major cause of cracking. Keeping water away from the foundation, especially during heavy rain, also helps protect the concrete underneath.
Avoiding excessive weight on already damaged concrete, like parking heavy vehicles on a cracked driveway, gives the repair a better chance of holding. Finally, inspecting cracks regularly lets you catch new problems early, before they grow into something that needs a bigger repair.
How Long Does Concrete Crack Repair Last?
How long a repair lasts depends on several factors, including the type of crack, the repair material used, and how well the underlying cause was addressed. A simple filler on a hairline crack might last for years, while a patch applied without addressing an ongoing drainage issue may need to be redone sooner.
Some cracks return, not because the repair was done incorrectly, but because the original cause of the cracking was never fixed. If soil movement or poor drainage caused the crack in the first place, a new crack may eventually form nearby even after a solid repair.
This is why fixing the underlying cause matters just as much as the repair itself. Addressing drainage, soil issues, or structural concerns alongside the crack repair gives you a much better chance of a lasting fix.
Need Help With a Concrete Crack in Phoenix, AZ?
If you are dealing with a concrete crack that seems too big, too deep, or just not going away, S&S Paving & Construction is here to help. Our team in Phoenix, AZ has the experience to evaluate driveways, sidewalks, patios, and slabs, and recommend the right repair for your specific situation. Contact us today for a free estimate and let our team help you protect your concrete for years to come.
Conclusion
Small, stable cracks in concrete can often be repaired successfully with proper cleaning, the right repair material, and careful application. Taking the time to identify the type of crack and choosing the correct product makes a real difference in how long the repair lasts.
However, large, growing, or structural cracks are a different story. These should be inspected by a professional before any repair is attempted, since they can point to issues with drainage, soil, or the structure itself that a simple patch will not solve.
Frequently Asked Questions
Can I fix concrete cracks myself?
Yes, for small, stable cracks like hairline cracks and minor surface cracks, a DIY repair with the right filler or patching compound usually works well. Wider, deeper, or structural cracks are better handled by a professional.
What is the best way to fill cracks in concrete?
Clean the crack thoroughly, then apply a repair product suited to the crack’s size, such as a liquid filler for thin cracks or a patching compound for wider ones, and smooth the surface once applied.
Should I use concrete filler or caulk for cracks?
Concrete filler is generally better for structural repairs, since it is designed to bond with concrete and hold up under weight. Caulk, particularly polyurethane sealant, works well for cracks that need flexibility, like those exposed to temperature changes.
Can you repair a concrete crack without replacing the slab?
In many cases, yes. Most small to medium cracks can be repaired without replacing the entire slab. Replacement is usually only necessary for extensive structural damage or repeated cracking that repairs cannot resolve.
When is a concrete crack a serious problem?
A crack becomes a serious concern when it is wide, growing, uneven, or paired with signs like sinking concrete or water intrusion. These signs often point to a deeper issue that needs professional evaluation.
How long does concrete crack filler take to dry?
Drying time varies by product, but many concrete crack fillers are ready for light foot traffic within a few hours and fully cured within 24 to 48 hours. Always check the specific product label for exact timing.
