Your sidewalk and driveway are important parts of your property; but almost nobody talks about how to maintain them or what problem signs to look for when they are damaged. There are different things that can warp your concrete slabs and deteriorate them, but one of the most disruptive problems comes in the form of concrete settling.
Concrete settling occurs when there’s a gap under the slab due to soil displacement. A slab cannot stay stable if it has an unstable foundation, so it sinks and settles against the gap.
Concrete settling is dangerous, especially if it happens on your sidewalk. You, your family, and members of your community can get hurt when walking on an uneven sidewalk. Here are some problem signs you can catch and repair early to protect your home.
Signs of Driveway and Sidewalk Settling
Detecting concrete slab settling early is key if you want to prevent injuries and you want to protect your car from a settling driveway. Unless you know where to look, you won’t be able to detect the problem signs early. Slab settling is something that happens slowly, so most homeowners realize there’s a problem after the settling has advanced considerably.
Keep a close eye on your driveway and sidewalk and see if you can spot any of the following problem signs:
A problem sign you can feel instead of see is flimsiness. If you step on a concrete slab and it wobbles, it’s settling. Often, the gap under the soil isn’t significant enough yet for the slab to sink. This is why slabs often feel loose. Even if your driveway is perfectly even, any kind of flimsiness indicates a problem you need to look into.
When you notice flimsiness in a slab, don’t continue to put any weight on it for two reasons. For one, concrete cracks a lot easier when it doesn’t have a stable layer of soil underneath. This is due to its terrible tensile strength. You could end up breaking the slab in half if you continue to walk on it. This is the reason sidewalk slabs are more likely to break when settling since they are walked on daily.
The second reason is that walking on it can cause further soil displacement. Too much weight on loose, shifty soil will only make the gap wider. This will accelerate the settling process until the slab finally sinks.
Tensile strength refers to a material’s ability to resist breaking under pressure. Concrete slabs have pretty bad tensile strength in comparison to their compression strength. However, they can bear heavy loads a lot better if they are resting on an even foundation. An even foundation allows them to disperse the pressure evenly throughout the slab so that the overall tension it has to endure is bearable.
If the concrete slab is settling, it cannot disperse the pressure evenly, causing it to crack under too much pressure. A cracked concrete slab is a lot more difficult to repair than one that is fully intact. It can be done, but not if the damage is too severe.
Void Under the Slab
Visually seeing the signs of settling can be difficult because all the action is happening underneath the concrete. However, you might be able to get a look at what’s going on if you look at the slabs at the edge of your sidewalk or driveway.
The exposed soil right next to your slab will get displaced a lot faster than the soil under the slab. Because it’s uncovered, it gets rained on, the freeze-thaw cycle will have more of an effect on it, and it’s vulnerable to other displacive elements like wind and human or animal activity.
As the soil wears down, a small indent will form next to the slab. This indent only makes it easier for moisture to get under the slab and erode the soil. If you notice that the underside of the slab is exposed by a void next to the concrete, you’ll know that the slab will eventually settle against it.
When slabs first begin to settle, the unevenness is minimal. Usually, homeowners don’t realize that settling has occurred until half the slab is an inch lower than the others. That said, there is a trick to detecting settling early, and that’s to observe your concrete after it has rained. When concrete slabs begin to settle, it might not be obvious, but a minor indent will form. This changes the way that water flows around your driveway and might lead to some pooling water.
Potholes appear in more places than just the streets. If there’s significant settling, they can appear on your driveway or sidewalk. Potholes are more likely to occur on your driveway than on your sidewalk because it’s caused by cars going over the slab.
If the void under the concrete is right in the middle of the slab, too much weight can cause a pothole. Driving your car over the unsupported section of the slab will cause the concrete to cave in.
A pothole is not something you can just fill in yourself if you want to repair the slab. Even if the gap is covered, you still need to be able to support the slab with a stable material. Or else, the soil will erode and the settling will continue.
The Causes of Concrete Settling
There are many reasons as to why the soil under your slab has eroded. Any kind of displacement it experiences can open the door for a gap to form that the slab can settle against in the future. This can be really frustrating as a homeowner since there’s nothing anybody can do to combat erosion. It all happens under the slab, so it’s not something we can even see happening.
Understanding the causes can help us detect the circumstances in which soil can erode. They may not all be preventable, especially those caused by nature, but they can help you make changes to slow down the settling process.
The number one reason for concrete slab settling in mid-Atlantic states is soil washout. Soil washout refers to the erosion of topsoil due to a stream of flowing water. As the water travels down the surface of the soil, it brings along the soil particles. A significant amount of erosion leaves an indent of the path the water took as it was streaming down.
Cities like Baltimore, Maryland, and Charleston, West Virginia, have sandy, fine-grain soils. These kinds of soils aren’t able to compact closely together as well as other soils can, so they are loose and shifty. Water has a harder time washing out dense soil but is able to do away with sand without much effort.
It also doesn’t help that there is a lot of sloped terrain around Virginia and West Virginia. Inclines accelerate soil washout since gravity is able to pull down the soil particles as the gush of water wades through.
The more streams of water the soil has to endure, the more it will wash out. Unfortunately for the homeowners in places like Washington, D.C., and Richmond and Manassas, Virginia, there’s enough water to change the terrain of an entire property.
Because of the yearly tropical storms, heavy rainfall is something your soil has to experience frequently. Even if the hurricanes have settled down by the time they reach your city, because of the high elevation terrain, the rainwater from the storm gets carried down from the mountains to flood your property.
While there isn’t much that can be done due to natural disasters such as flooding and tropical storms, there are things you can do to limit the amount of water your soil is exposed to. The key to preventing slab settling is making sure that your concrete and the soil around it come in contact with as little moisture as possible so that washout erosion is discouraged. Things like improving your yard drainage, re-landscaping your yard, and covering your driveway will give your slab a few more years of stability.
The Freeze-Thaw Effect
The freeze-thaw effect is a term used to describe the cycle of water freezing and thawing during the winter. When your concrete absorbs moisture from the snow and that moisture makes its way into the soil, it can cause displacement when the temperature falls.
When ice freezes, it expands and pushes the soil particles apart until it can’t expand anymore. Once the ice thaws, the water gets drained away, but the resulting gaps left by the solid ice stays and loosens up the soil.
Earthquakes are a minor disturbance in comparison to the floods that destroy properties during storm season. Still, the East Coast Fault Line does play a part in soil disruption, even if it is minor. When the earth trembles, it’s capable of shaking up the soil particles until the soil layer isn’t as even as it was after the driveway and sidewalk were constructed.
For clay soils, which tend to be densely packed, earthquakes don’t do as much damage. But for the sandy soils of the mid-Atlantic states, every tremor brings the slab one step closer to settling.
What Should I Do if My Driveway and Sideway Are Settling?
The moment you notice that the slabs on your driveway and sidewalk are settling, you need to contact an expert for repairs. Many homeowners believe that they have to replace the slab once it begins settling, but the problem can easily be remedied with concrete lifting.
Concrete lifting is a slab repair method that involves pumping in a material under the slab until there is enough to support the concrete and lift it back to its original place. There are different types of concrete lifting methods available, so educate yourself well to see which method is the best for you and your home. The most desired method by homeowners is polyurethane foam injections due to its reliability and non-invasive installation procedure.