Wondering: why do sidewalks have cracks? Crack formation is an inevitable occurrence on every sidewalk. There are various reasons behind this phenomenon.
Invasive roots, an unstable soil base, poor concrete quality, and random soil settling can cause cracked sidewalks.
Builders also create cracks called expansion joints in the sidewalks as a part of their construction process!
In this post, we’ll explain each of these reasons in detail. More importantly, we’ll provide solutions for addressing all types of sidewalk cracks you might encounter.
There are multiple reasons why cracks may be present in your sidewalk. Here are the most common ones:
1 – Expansion Joints: Man-Made Cracks
Sidewalk concrete is a mixture of crushed rocks, cement, and water. One of the disadvantages of this blend is that as it dries, it shrinks slightly.
This slight shrinking leads to the formation of cracks.
Likewise, concrete contracts with cold and expands with heat. The repetition of this cycle over time causes the formation of small cracks.
If the concrete develops random cracks due to any of the above reasons, it may eventually cause the sidewalk to break apart.
To prevent this scenario, builders create man-made cracks on the sidewalks called expansion joints.
These joints reduce and prevent the occurrence of random cracks in the concrete. As a result, they preserve the structure and strength of the sidewalk.
Giant tree roots can contribute to the formation of cracks in sidewalks. A tree near the sidewalk is likely to grow roots underneath the concrete.
As roots grow, they become stronger and exert significant force on the concrete.
Over time, this high pressure causes the sidewalk to buckle or heave up. As a result, the sidewalk starts to develop cracks of varying sizes.
In areas with high rainfall frequency, the soil under the sidewalks may experience erosion as the water runs through it. That way, the soil can gradually loosen and create voids.
As these voids get larger, the concrete above them loses its soil support. Consequently, it starts to develop cracks.
Before pouring the concrete onto the sidewalk, builders compact the soil beneath it. If they don’t do it correctly, the ground becomes unstable under the slab.
That’s because the soil base will settle randomly in some areas more than others, creating many voids under the sidewalk.
Consequently, voids create many unsupported areas under the concrete. As a result, the sidewalks form cracks in these areas.
Unfortunately, cracks caused by random soil settling can be severe. They might even necessitate the entire sidewalk to be redone.
The quality of the concrete used in paving sidewalks plays a significant role in the strength of their structure.
That way, builders should prepare concrete with a minimum strength of at least 3000–4000 psi for sidewalks.
If the concrete has a concentration lower than the recommended level, it’ll likely develop cracks. This is also the case if the concrete is mixed in incorrect ratios.
Yes, you can repair most cracked sidewalks. Depending on the causes of the cracks and their size, you can pick the most suitable solution of the following:
If your sidewalk develops small cracks due to expansion and contraction, you can easily fix them.
All you need is to fill these cracks with a liquid crack filler. These fillers are available in bottles of various sizes. They’re affordable and simple to use.
To fix the cracks, follow these steps:
- Take the filler bottle and pour some of the liquid into the cracks.
- Allow the liquid to dry for a few hours.
- Once the liquid has dried, the cracks will be repaired.
To repair medium-size cracks, you can fill them with homemade mortar. To do this, prepare the mortar by mixing sand, Portland cement, lime, and water.
Then, use this mixture to fill the cracks. This is the most affordable solution you can use for medium-sized cracks.
However, if you prefer to use pre-made solutions, here are the three most effective products you can choose from:
- Tube Cement
- Flexible Masonry Caulk
- Concrete Patch Mix
Whatever solution you select, ensure to apply it correctly. To achieve this, clean the cracks using a bristle brush before using these products.
As you clean, remove any debris or dirt from the cracks. In addition, read the product instructions carefully and follow them to achieve the desired results.
Before repairing the large cracks, you need first to fix the underlying problem that causes them. This is to ensure the concrete won’t form further cracks after the repair.
The two most common underlying causes of large cracks are:
- Soil voids: inspect the soil for gaps. If any exist, you need to fill them. You also need to support the ground with gravel to prevent the formation of future voids.
- Invasive roots: if the roots of a nearby tree are causing cracks in your sidewalk, consider either removing the tree or moving the sidewalk.
After solving the underlying problem, use fresh concrete to fix the large cracks.
To do this, follow these steps:
- Clean the cracked area using a bristle brush. Remove all the debris and dirt from the cracks.
- Prepare your fresh concrete.
- Apply a bonding liquid to the cracks using a paintbrush. Make sure to cover the whole fissure with the liquid.
- Pour the fresh concrete and firmly press it into the crack using a trowel. Ensure the concrete gets as deep as possible into the fissure.
- Distribute the concrete evenly over the surface of the crack. The fissure’s surface should be level with the surrounding area of the sidewalk.
- Clean off any excessive concrete on the cracks’ surface using a sponge.
- Allow the concrete from 24 to 48 hours to dry.
Huge cracks usually occur due to poor-quality concrete and unstable soil. Because of their massive size, repairing them requires considerable time and resources.
In these cases, the only solution is to fix the underlying problem and completely redo the affected part of the sidewalk.
The man-made lines or cracks created by sidewalk builders are called expansion joints. Some people also refer to them as control joints or lines.
The name is derived from their function of allowing the concrete to expand and contract safely without forming random cracks.
The distance between sidewalk expansion joints can vary from one location to another. However, on average, builders place a contraction joint every 8 to 15 feet.
That’s because the recommended spacing between sidewalk cracks shouldn’t exceed two to three times the thickness of the concrete in inches.
For example, if the concrete is 4 inches thick, the lines should be placed 8 to 12 feet apart.
Homeowners’ insurance may cover sidewalk repairs if the damage meets certain conditions. In most homeowners insurance policies, sidewalks are classified as” other structures.”
That way, the insurance policy will cover their damage if caused by one of the listed perils.
These perils include unexpected accidents like fires, criminal activities, and extreme weather.
Nonetheless, if the damage is due to factors other than previously mentioned, your insurance won’t likely cover it.
By now, the answer to “Why do sidewalks have cracks?” is clear! The cracks might be a preventive measure, such as the expansion joints made by the builders.
However, cracks can have a damaging effect on the sidewalk if they appear randomly.
This can occur for many reasons, including poor concrete quality, unstable soil, and invasive roots. Random soil settling can also contribute to this problem.
Regardless of the cause, you can refer to the above-mentioned solutions to effectively repair cracks in your sidewalk.
I have a bachelor’s degree in Computer Information Systems and over 10 years of experience working in IT. As a homeowner, I love working on projects around the house, and as a father, I love investigating various ways to keep my family safe (whether or not this involves tech). I’ve also played guitar for almost 20 years and love writing music, although it’s hard to find the time these days.