Why Is My Concrete Driveway or Sidewalk Sinking? (+ Ways to Fix It)

Your driveway is sinking. Your sidewalk is sloping. First, you’re like, “What the heck is going on and how can I stop it?” Followed shortly by even more questions like: 

• What should I do? 
• Can this be fixed? 
• What’s the best way?

Not to worry, at Anchor Foundation Repair, we’ve helped thousands of homeowners restore their concrete to the proper elevation. We know all the reasons it happens and all the options available to help slow down or prevent uneven concrete. The good news is that you don’t have to resort to tearing it all out, there are alternatives.

In this article, we will explain the reasons that concrete flatwork sinks and what you can do to minimize or prevent sinking. We also offer the best options to restore your concrete to a safer, more usable condition.

7 Reasons Why Your Concrete Driveway or Sidewalk Is Sinking

People want to know *why* things happen. I get it. You don’t want *whatever it is* to happen again in the future, so understanding how your concrete sank in the first place is just as important as fixing the problem. 

As for your sinking and sloping concrete issues, here are some reasons this sort of issue develops:

1. Poor initial construction
2. Inadequate initial soil compaction
3. Gravitational forces
4. Expansive clay soil
5. Voids created by water source issues
6. Tree root issues
7. The basic design of concrete flatwork

These problem sources deserve more detail since this is the main point of the article. So let’s *sink* our teeth into some meatier explanations on the reasons your concrete gets off-kilter.

1. Poor Initial Construction

Making concrete surfaces seems pretty simple, but there are many parts of the process where things could go wrong with concrete. They might not get the concrete mix quite right causing strength issues. They might not pour it thick enough. They might not put any or enough reinforcement in the concrete to support the required weight. 

The temperature or weather conditions might not be optimal during the pour . . . and there’s probably some other stuff that I am forgetting.

Operator error, poor procedures, simple mistakes, bad habits, unfavorable conditions, untrained workers – all these factors could play a part in your concrete driveway or sidewalk sinking.

2. Inadequate Initial Soil Compaction

Another essential aspect of the initial construction is soil compaction. As with many construction projects, prep work is everything. Laying the literal *groundwork* properly is very important in concrete flatwork. Getting all the air pockets and unevenness out of the soil helps to keep your finished concrete level and in place.

If soil compaction is done poorly, unevenly, or not much at all, your concrete surface is not resting in an optimal environment and sinking problems can more easily develop.

3. Gravitational Forces

Anytime something is built on the ground that has considerable mass, whether it’s a full-sized slab foundation or a concrete driveway, gravity takes effect. Heavy concrete things will compact the soil further after construction, even if the soil is well compacted in the first place. 

This is called initial settlement. Heavy stuff will sink into the ground a little because, well . . . it’s heavy and it happens. Gravity keeps on happening all the time and could always contribute in part to a concrete surface sinking.

4. Expansive Clay Soil

We have expansive clay soils throughout Texas and in many other parts of the country too. This type of soil expands when wet and contracts when dry. The longer it stays wet, the more it expands. The longer it stays dry, the more it contracts. If it sounds like the dirt is moving, it is.

Imagine throwing a flat sponge into a tub of water and watching it float there, bobbing up and down on the rippling surface. That’s about what your little concrete panel is doing sitting on top of the soil. 

Expansive soil moves a lot, especially when the weather goes from one extreme to another like it does here in Texas. We get periods of intense rainfall and periods of significant drought. So that means that every year the soil goes through movement cycles of seasonal settlement and rebounding. All that movement can make concrete panels tilt, sink, heave, or all of the above!

5. Voids Created by Water Source Issues

Water from several sources can wreak havoc on concrete surfaces. Rainfall runoff, improper grading, or poor drainage can cause water to hang around too long or flow near concrete causing settlement and erosion. 

Water from gutters and downspouts can often be directed towards driveways and sidewalks. This seems like a good idea to have the water coming off your roof flowing onto these concrete surfaces instead of into the yard, but after a while it causes issues. 

The focused water flow slowly and subtly erodes dirt from under the surface both enabling settlement and further erosion. Then, you wind up with sunken concrete right where the water flow occurs. It’s happening to my own driveway right now.

Broken irrigation lines and proximity to pools also cause concrete flatwork to sink and become uneven. Anytime you’ve got water, whether it’s wanted or unwanted, it can negatively impact the condition of your concrete.

6. Tree Root Issues

Tree roots can cause two distinct problems with concrete flatwork: lifting and sinking.

Big tree roots close to the surface can grow underneath concrete. Sidewalks and driveway panels get pushed up causing misalignments and tripping hazards. So it might look like one side of a concrete panel is sinking, but it’s really that the other side is getting pushed up and causing panels to tilt.

Trees can also die or fall over and have to be removed. If those trees are close to a concrete surface (or even your foundation), as the underground tree roots decay and rot away, voids develop in the soil and cause concrete panels to sink. This is happening to my sidewalk right now too . . . 

7. The Basic Design of Concrete Flatwork

Even if a piece of concrete flatwork is perfectly made, under ideal conditions, with excellent soil compaction, flawless drainage patterns, and no nearby trees, it’s simply not built to withstand everything that gets thrown at it. Basic concrete driveways and sidewalks are, for lack of a better word . . . basic. 

Outdoor concrete surfaces around homes are not built the same as slab foundations. Residential flatwork is also not built the same as industrial flatwork i.e. roadways, airport runways, etc. Heck, concrete around a single-family home isn’t even built as well as the nice basketball court at your local park.

Residential flatwork does not have grade beams that go deeper into the ground like slab foundations do. Both residential driveways and sidewalk panels are relatively thin and don’t penetrate into the ground. Sidewalks may not be reinforced. These things are not made to last for an eternity and they need to be economical so that individual people can buy them. 

Basic concrete surfaces are made just good enough to create a decent surface for you to walk on or park your car on. It’s not worth it to install residential concrete flatwork that’s 12 inches thick with 4 ft grade beams or industrial footings. You couldn’t afford it and it’s a bit of overkill. By nature, the simple, non-heavy-duty, cost-effective design makes it more susceptible to sinking and movement.

Ways To Prevent or Minimize Concrete Sinking Further

Let’s sort through the detailed reasons your concrete may be sinking to see if we can do anything about them in the form of prevention or minimizing further impact.

To be honest and upfront, most of the causes of your sunken concrete are impossible to control, so there’s only so much you can do. Here’s the list again only I’m going to cross off the ones you frankly can’t do anything about:

1. Poor initial construction
2. Inadequate initial soil compaction
3. Gravitational forces
4. Expansive clay soil
5. Voids created by water source issues
6. Tree root issues
7. The basic design of concrete flatwork

Unless you opt for the full replacement of your concrete surface, you can’t do a darn thing about how the concrete was already constructed. You also can’t do anything about natural forces like gravity and soil behavior (but let me know if you figure something out so we can both get rich). 

SO, you’re left with only a couple of things you can even *attempt* to control. You’re still dealing with natural stuff like water and trees, but you can at least have a little influence over these factors.

Preventing or Minimizing Concrete Voids Created by Water Source Issues

This shouldn’t be real *groundbreaking* advice, but if you’ve got water messing with your concrete surfaces, you need to find ways to get rid of it. 

Work on your surface drainage. Fill in low spots in your yard. Fix those gutters. Extend your downspouts farther away from surfaces. Address broken irrigation systems asap. Anything you can do to keep water from causing erosion and settlement is what needs to be done. But it’s a slow process so just be prepared to work on things little by little towards improvement.

Here are some drainage solution ideas that may help. This article is geared towards drainage around your foundation, but they mostly apply to concrete flatwork as well.

Preventing or Minimizing Concrete Issues Caused by Tree Roots

Tree root situations are more difficult to deal with. If your tree is healthy and doing fine, there’s not much you would really want to do. Who wants to cut down a perfectly good tree providing shade for your home? Hopefully no one.

If you’ve got healthy tree roots pushing up on your concrete, you might have to just deal with the situation or possibly remove the concrete. Maybe you could relocate a sidewalk path, but you most likely couldn’t do that for a concrete driveway, unfortunately. For a driveway, perhaps converting to a gravel drive would work in some places.

If a tree is suffering and unhealthy, it may be time to remove it. But when you do, you need to watch for concrete settlement where any tree roots you couldn’t remove from the ground begin to decay. Make sure the hole left by the tree removal gets filled in properly. You might have to keep filling in holes for a while as roots decay.

It might be possible to fill voids under concrete surfaces left by decaying tree roots. It all depends on the surface condition and the situation around your home. Here’s an article that explains how that might work for you: How To Fix Erosion, Voids, or the Hollow Sound Under Your Concrete.

What Happens If Your Concrete Keeps Sinking

Eventually, your concrete should stop sinking, but no one knows when that will be. Also, if you allow it to continue sinking lower and lower, it just results in bigger issues and more damage, cracks, and risk. 

If your concrete keeps sinking and settling no matter what remedies you have applied, you should do something about it at some point. Tripping hazards are liability issues for property owners. You don’t want anyone getting hurt, and you don’t want anyone suing you over the injuries either.

If your concrete is in bad shape anyway, crumbling and cracking significantly, concrete removal and replacement might be your best bet.

If your concrete is generally in good condition, but just misaligned and sunken in places, then you have a lot more options. Check out this article for six feasible choices to handle sunken concrete. BTW, one of the options is for mud jacking, which is a service that we provide.

What Is the Best Way to Repair Sunken Concrete?

Now that you know about all the reasons your concrete might be sinking, you’re likely ready to do something about it. Either you’re going to start working on poor drainage or other situations you can control, or you might be ready to repair your sunken concrete. 

Wanna know the fastest option? It’s concrete raising, or concrete lifting, or well, it goes by a lot of names and there are even a couple of methods we can tell you about.

At Anchor Foundation Repair, we make it a point to educate homeowners about all their options. After 40+ years in business, we want you to know as much about settled concrete as we do including all the methods and options available to you even if we don’t provide them.

To learn more about the concept of raising sunken concrete, check out: What Is Concrete Slab Jacking? (Definition, Methods, Cost).