concrete sinking causes

Concrete Sinking Causes and Prevention

At Lift-Up Concrete Lifting, LLC, we’re here to provide you with comprehensive services for concrete lifting, raising and leveling. Whether you have issues with residential, commercial or municipal concrete, we can help you assess and manage settled concrete in healthy and permanent ways.

Concrete is a fantastic material for a wide variety of project areas, with great durability and economical qualities that stop it from being wasteful. But that doesn’t mean it’s perfect – it can still crack, chip, crumble and sink after settling. Let’s look at some of the reasons why your concrete might sink noticeably, plus a few precautions you can take to help limit this from happening.

Causes of Sinking

There are two primary causes of concrete sinking into the ground:

  • Base construction issues: When concrete slabs are installed in a given walkway, driveway or similar area, they’re placed over a base that’s built prior to construction. But not all bases are created equal – some might not be compacted in the right ways, while others might use the wrong materials, such as loose aggregates or softer soils that aren’t dense enough. When this happens, concrete is liable to sink. 

    For example, a common location where you might find sunken concrete is the perimeter of the concrete foundation. This perimeter is often called the “over-dig” area, one that’s set slightly further out than the actual foundation to allow workers to move around the foundation easily. If the over-dig area is not backfilled properly, it will settle in and can easily cause sinking.

  • Water erosion: In proper concrete jobs, a seal is created between the upper part of the work and the concrete slab. But in some cases, water is allowed to intrude below the slab. This will cause erosion to take place, and will also lead to issues in colder climates – water will freeze and expand, then shrink back down again when the weather warms up. This creates voids in the concrete, which can lead to sinking. Anywhere water is allowed to flow below the seal can create this issue. Broken pipes or sprinklers are a common cause.

Preventing Concrete Sinking

There are several things you can do to help prevent sinking from taking place in your concrete:

  • Seal all cracks or openings near concrete using either silicone or polyurethane caulk. If you have larger caps to fill, use backer rod and then place caulk material on top.

  • Pack any open sides of concrete slab with soil to make sure water cannot slip below them.

  • Move all water runoff downspouts to at least five feet away from concrete slabs, and even further if possible.

  • During new concrete installation, make sure the base is both compacted and at least four inches deep. One good test here is to stomp your feet around the entire base – it should not move at all when you do this.

For more on the causes of concrete sinking and how to prevent it, or to learn about any of our concrete raising or leveling services, speak to the pros at Lift-Up Concrete Lifting, LLC today.