Skip to main content

Your Sidewalk Slab is Sinking, Here’s Why

You’ve got a beautiful home, an immaculate yard… and a section of sidewalk slowly sinking into it.

If you have a concrete sidewalk, walkway, or path in your front yard, there is always a danger that sections of it may start cracking, shifting and sinking into the soil. When this happens, you may ask yourself, “Why is this happening and what can be done to stop it?”

Sidewalk Slab is SinkingThere are a few common causes behind sinking concrete slabs. The most common are:

  1. Erosion
  2. Decomposition
  3. Settling / Disturbing native soil

What water problems can cause concrete damage?

Erosion is a common cause of voids forming below your concrete. Usually, it’s caused by broken sprinkler lines and downspouts. The water in these leaks is already under the concrete and the water starts washing away the dirt, where it can’t be seen. We get a lot of snow, hail, and rain here in Utah County and Salt Lake County; sometimes we get all three in one day! However, precipitation doesn’t have much of an impact on the concrete or the ground beneath it.

However, the weather/temperature can cause a pipe to freezes, swells, and cracks in the winter. These cracks will begin to leak when it eventually thaws out again, and you might not realize it if it’s under a concrete slab, until the slab starts to disappear. Keep an eye on your water bill—if it spikes one month, you might want to call someone to have a look at your pipes before the erosion sets in.

What exactly is rotting under your concrete???

Not to worry…it isn’t likely that anything nefarious has taken place on your property, but there are things in the ground that can decompose and leave small voids. Things like:

  • Previous owners pets
  • Random things those pets buried in life
  • Time capsules
  • Tree roots (the most likely cause)

Tree roots can be a problem for concrete, while a tree is alive. The roots of trees eventually expand and raise/crack concrete slabs, even if the concrete is nowhere near the tree. Roots left behind from long-dead trees can result in small voids, but they are generally not large enough to cause a problem for your concrete. So again, not to worry, these minor cavities are not likely to have any impact on your concrete sidewalk or other slabs.

A house on a hill can’t be hidden… or supported.

Whether your home is on the side of a mountain, the top of a hill, or down in the valley, it’s unlikely that your entire property is completely level. Concrete is heavy and tends to settle over time. Whether it supports a house or just your kids’ bikes, there is a lot of weight in a small space and the ground underneath it isn’t as firm as slab itself.

Shifting dirt is the most common and most serious cause of sinking concrete slabs. When the native soil is disturbed there can be areas of more and less densely packed dirt. So, your home might have been built on a previous lot with a back-filled basement, that dirt is now shifting and settling and can’t hold up the concrete anymore. If your property wasn’t properly compacted before concrete sidewalks or slabs were poured, the variation of density beneath your feet will start to even out and the sidewalk may start to sink.

What you can do to fix your sunken sidewalk or concrete slab

It really isn’t important, in the grand scheme of things, if your slab is sinking because of erosion, an ancient pet burial ground or an unsettling foundation. The fact is you have a problem and need it fixed. The traditional way would be to get a team out there with picks and hammers, let them make a big mess, then re-pour the section of sidewalk. Just wait one week and you’ll be back to normal, not to mention the high cost of labor, time and material you’ll have to pay for. An added benefit, your new concrete won’t match the rest of your sidewalk’s texture, color or shape…#ConversationPiece!


You could give us a call. Landmark Lifting uses a polyurethane foam compound that lifts your slab back into its original position in a matter of minutes!

  • Our compound is inert, which means it won’t leach chemicals into the groundwater.
  • Our foam expands in 15 seconds
  • Our foam can hold 6,000 lbs per square foot.
  • Our foam cures in 15 – 30 minutes

Let us fix your sidewalk for you and you’ll be back on it by the time we’re done packing up our tools. Doesn’t that sound good?

Call us at (801) 420-5117