Cracks in concrete walls can be a common problem in homes, but they are usually easy to fix. Whether it’s a small hairline crack or something more serious, this guide will help you understand what causes them and how to repair them. Don’t worry—fixing cracks doesn’t need to be difficult. We’ll walk you through 12 easy steps, so even children can understand how to tackle these cracks safely and effectively.
Let’s dive in and explore how to fix those cracks one by one!
Types of Cracks in Concrete
Before we jump into how to fix cracks, it’s important to understand the different types of cracks that can appear in concrete. Knowing what kind of crack you’re dealing with will help you choose the right repair method.
Here are the most common types of cracks in concrete:
- Shrinkage Cracks: These appear when concrete dries and shrinks, leaving tiny lines on the surface.
- Overloading Cracks: Heavyweight on concrete surfaces can cause cracks when the load exceeds what the slab was designed to bear.
- Hairline Cracks: These small cracks are very thin and typically harmless, but they should still be monitored.
- Settling Slab Cracks: These occur when the ground beneath the concrete shifts or sinks, causing the slab to settle unevenly.
- Heaving Slab Cracks: Caused by the ground pushing up on the slab, often due to freezing temperatures.
- Foundation Settlement Cracks: These vertical or diagonal cracks happen when a foundation settles unevenly.
- Structural Cracks: Serious cracks that affect load-bearing walls or other critical parts of a building.
- Crazing Cracks: Tiny cracks that form a pattern like a web and are mostly surface-level issues.
- Crusting Cracks: These occur when the surface of concrete dries too quickly, leading to cracks.
- Re-Entrant Corner Cracks: Found at corners of windows or doors, caused by stress concentration.
- Internal Reinforcement Corrosion Cracks: When steel inside concrete rusts, it can lead to cracks as it expands.
Now that we know the types of cracks, let’s explore how to fix them!
1. Shrinkage Cracks
What are they?
Shrinkage cracks are tiny lines that often appear in freshly poured concrete as it dries. These cracks are very common and are usually not a cause for concern.
How to fix them:
The easiest way to handle shrinkage cracks is by filling them with a concrete crack filler. You can buy this from any local hardware store. Simply apply the filler to the crack using a caulking gun, smooth it out, and let it dry.
2. Overloading Cracks
What are they?
Overloading cracks happen when too much weight is placed on the concrete surface. This can happen on floors or slabs that weren’t designed to hold heavy loads.
How to fix them:
To fix these cracks, you first need to remove the excess load causing the damage. Once that’s done, clean the crack, and apply a strong epoxy concrete repair solution. This will help bond the concrete back together and strengthen the area.
3. Hairline Cracks
What are they?
Hairline cracks are super thin cracks, often less than a millimeter wide. They are usually not a structural issue but can be a sign of future problems if ignored.
How to fix them:
For hairline cracks, you will need a liquid crack sealer. This type of sealer is very thin, so it can seep deep into the cracks and fill them. Use a brush to make sure it spreads evenly across the surface.
4. Settling Slab Cracks
What are they?
Settling slab cracks appear when the ground beneath the concrete shifts or sinks. This causes the slab to move, leading to cracks in the surface.
How to fix them:
These cracks often require a more solid solution. First, clean the crack thoroughly. Then, use a concrete patching compound to fill in the gaps. For larger cracks, you might need to reinforce the area with metal brackets or rebar.
5. Heaving Slab Cracks
What are they?
Heaving slab cracks happen when the ground beneath the concrete pushes up, causing the slab to lift. This is common in areas with freezing temperatures, as the ground expands when it freezes.
How to fix them:
Start by removing any debris or broken pieces of concrete around the crack. Use a cold chisel and hammer to widen the crack slightly, then apply a concrete filler. For serious heaving issues, you might need professional help to level the slab.
6. Foundation Settlement Cracks
What are they?
Foundation settlement cracks occur when the foundation of a house settles unevenly. These cracks can be vertical or diagonal and may indicate foundation issues.
How to fix them:
Foundation cracks need extra care. First, examine the crack closely. For smaller cracks, use a polyurethane sealant. For larger cracks, consider hiring a professional to assess whether your foundation needs reinforcement or leveling.
7. Structural Cracks
What are they?
Structural cracks are more severe because they affect the strength of the building. They often appear in load-bearing walls or columns and need immediate attention.
How to fix them:
Structural cracks require professional intervention. A structural engineer will need to assess the damage. Once the cause is identified, repairs may involve reinforcing the wall with steel braces or epoxy injections to restore the concrete’s strength.
8. Crazing Cracks
What are they?
Crazing cracks look like a web of fine lines on the surface of the concrete. They don’t go deep and are more of a surface-level problem caused by improper curing or drying.
How to fix them:
Crazing cracks don’t need heavy-duty fixes. You can apply a concrete resurfacer, which is a thin layer of concrete mix that will cover the cracks and give the surface a smooth appearance again.
9. Crusting Cracks
What are they?
Crusting cracks happen when the surface of the concrete dries too quickly, often due to weather conditions. The top layer hardens and cracks, while the rest of the concrete is still wet.
How to fix them:
To fix crusting cracks, you can apply a thin cement overlay on the affected area. Make sure to cure the concrete properly this time, keeping it moist as it dries to prevent future crusting.
10. Re-Entrant Corner Cracks
What are they?
Re-entrant corner cracks appear at corners, especially where windows or doors are installed. They often happen because stress concentrates in these areas.
How to fix them:
To repair re-entrant corner cracks, you need to relieve the stress. Use a hammer and chisel to create a small groove at the tip of the crack, which will prevent it from growing. Fill the crack with a concrete patch and smooth it out.
11. Internal Reinforcement Corrosion Cracks
What are they?
When the steel reinforcement inside the concrete starts to rust, it expands, causing cracks. This type of crack is usually seen in older structures where moisture has gotten into the concrete.
How to fix them:
Internal reinforcement corrosion is a bit more complicated to fix. You’ll need to remove the damaged concrete around the steel, clean the rust off the steel rods, and then patch the area with fresh concrete. For major corrosion, professional assistance is recommended.
Conclusion
Cracks in concrete are common, but they don’t need to cause panic. Whether it’s a small hairline crack or a more serious issue like a foundation crack, there’s always a solution. By following these simple steps, you can handle most cracks yourself, making sure your concrete stays strong and durable.
If you ever feel overwhelmed or unsure, it’s always a good idea to call a professional, especially for larger or structural cracks. Matsu Painters is here to help with any of your repair needs, offering expertise in fixing concrete cracks and much more!