What Causes Concrete to Rise? Understanding Frost Heave and Slab Heaving

Most homeowners assume that concrete only sinks over time. Gravity pulls everything down, right?

So when a sidewalk panel suddenly juts upward, or a driveway section lifts and cracks at the joint, it feels counterintuitive. The concrete is going the wrong direction.

But rising concrete, also called heaving, is one of the most common slab issues we see in Colorado Springs. And the forces driving it are powerful enough to lift thousands of pounds of concrete without any hesitation.

Here is what is actually happening under your slab and what you can do about it.

Rising vs. Sinking: Two Sides of the Same Problem

Before we dig into the causes, it helps to understand how rising and sinking relate to each other.

When concrete sinks, the supporting soil beneath it has moved away. The slab drops into the gap.

When concrete rises, the soil or material beneath it is expanding. The slab is being pushed upward by pressure from below.

Both problems create uneven surfaces, trip hazards, and structural stress on the surrounding slabs. The difference lies entirely in the mechanism.

And in Colorado Springs, the conditions that cause heaving are everywhere.

Cause 1: Frost Heave (The Primary Culprit in Colorado)

Frost heave is the single most common cause of rising concrete along the Front Range.

The physics are straightforward:

Water in the soil freezes as temperatures drop below 32 degrees.
When water freezes, it expands by approximately 9% in volume.
That expansion pushes the soil upward.
The concrete sitting on top of that soil has no choice but to move with it.

But the real damage comes not from a single freeze, but from the cycle.

The Freeze-Thaw Cycle

Colorado Springs experiences over 100 freeze-thaw cycles per year. That is not an exaggeration.

On a typical February day, the temperature might hit 55 degrees in the afternoon sun and plunge to 15 degrees overnight. The soil freezes, thaws, freezes again, and thaws again, sometimes within the same 48-hour window.

Each cycle does cumulative damage:

Freezing phase: Ice lenses form in the soil, pushing upward and creating tiny lifts.
Thawing phase: The ice melts, but the soil does not always settle back to its original position. Air pockets remain.
Net effect: Over dozens of cycles, the soil profile under the slab becomes progressively uneven. Some areas rise. Others stay put. The slab cracks at the stress points.

Ice Lens Formation

The most damaging form of frost heave occurs when ice lenses form within the soil. These are horizontal layers of pure ice that grow as moisture migrates upward through capillary action toward the freezing front.

A single ice lens can grow to several inches thick, exerting enough pressure to lift a garage floor slab weighing over 10,000 pounds.

Soils most vulnerable to ice lens formation:

Silty soils (the worst offenders)
Fine sand with high moisture content
Clay soils with poor drainage

Well-drained gravel and coarse sand rarely produce significant frost heave because water drains away before it can freeze in place.

Cause 2: Expansive Clay Soils

If frost heave is the number one cause of seasonal heaving, expansive clay is the number one cause of chronic heaving.

Colorado Springs sits on some of the most reactive clay soils in the country. The dominant clay type along the Front Range is Bentonite, a mineral that absorbs water like a sponge and swells dramatically when wet.

The Expansion Numbers

Soil Type	Volume Change When Wet	Pressure Exerted
Sand/Gravel	Less than 1%	Negligible
Low-Plasticity Clay	3% to 5%	Moderate
Bentonite Clay	10% to 15%+	Up to 5,500 PSF

To put that in perspective, Bentonite can exert over 5,500 pounds of pressure per square foot when it saturates. That is more than enough to crack and lift any residential concrete slab.

The Swell-Shrink Cycle

Clay movement is not a one-time event. It is a repeating pattern tied to moisture levels:

Wet season (spring snowmelt, summer rain): The clay absorbs moisture, swells, and pushes the slab upward.
Dry season (late summer, fall): The clay loses moisture, contracts, and pulls away from the slab. Voids form. The concrete may sink slightly.
Next wet season: The clay swells again, but this time it may push the slab to a slightly different position.

Over years, this cycle produces the classic pattern of one panel rising while its neighbor drops, with cracks forming along the joints.

The Colorado Springs Soil Factor

Not every neighborhood in Colorado Springs sits on the same soil. The geological map of El Paso County is a complex patchwork:

Briargate and Northgate: Often built on Pierre Shale, which contains significant Bentonite.
Broadmoor area: Granite-based soils with less expansion risk.
Powers corridor: Mixed clay and fill soils from rapid development.
Old Colorado City: Older fill material with unpredictable behavior.

Knowing your soil type is the first step in understanding why your concrete is moving.

Cause 3: Tree Root Pressure

Tree roots are one of the most visible and dramatic causes of rising concrete. We see this constantly on sidewalks and pathways near mature trees.

How it happens:

Tree roots grow horizontally through the top 12 to 18 inches of soil, seeking moisture and nutrients. When they encounter a concrete slab, they do not stop. They grow under it, and as the root thickens over the years, it pushes the slab upward.

A root that starts at pencil thickness can grow to the diameter of your forearm within a decade. That gradual expansion exerts enormous hydraulic pressure against the underside of the concrete.

Trees most likely to cause heaving in Colorado Springs:

Silver Maple: Aggressive shallow root system. The number one offender.
Cottonwood: Fast-growing with extensive lateral roots.
Siberian Elm: Common in older neighborhoods. Roots follow water lines.
Blue Spruce: Surprising, but large specimens can develop significant surface roots.

For detailed solutions to root-related concrete problems, see our guide on tree roots lifting sidewalks.

Cause 4: Hydrostatic Pressure

When water accumulates beneath a slab faster than it can drain away, it creates hydrostatic pressure. This is water pushing upward against the bottom of the concrete.

Common scenarios:

High water table: After heavy spring snowmelt, the water table in some parts of Colorado Springs rises to within a few feet of the surface.
Poor drainage: A slab poured in a low spot without proper gravel base acts like a dam. Water pools underneath and pushes up.
Underground springs: More common than most people realize in the Pikes Peak region. Water moves through fractured rock and emerges in unexpected locations.

Hydrostatic pressure tends to affect garage floors and basement slabs more than exterior concrete, because these surfaces trap water rather than allowing it to flow away.

Cause 5: Construction Backfill Expansion

This cause is specific to newer construction, and it is more common than most builders will admit.

When a home is built, the foundation is excavated, and then the area around it is backfilled with soil. If that backfill contains expansive clay or is not properly compacted, it can swell significantly when it absorbs moisture from rain, irrigation, or snowmelt.

The result is rising concrete along the foundation perimeter, particularly affecting:

Front walkways and stoops
Patio slabs adjacent to the house
Driveway aprons near the garage

We frequently see this problem in homes that are 3 to 8 years old, which is the typical timeline for backfill soil to fully react to moisture cycles.

Signs Your Concrete Is Heaving (Not Sinking)

Heaving and sinking can look similar at first glance, because both create uneven surfaces. But the telltale signs of heaving are distinct:

One panel is higher than its neighbors rather than lower.
Cracks originate at the center of the slab and radiate outward (sinking cracks typically start at edges and corners).
The movement is seasonal. The slab rises in winter or spring and drops slightly in summer. This is a hallmark of frost heave or clay expansion.
You see root bumps. Visible humps or ridges along one side of the slab indicate root pressure beneath.
Doors stick seasonally. If the interior door nearest to the heaving slab jams in winter and opens freely in summer, the floor beneath it is moving with the frost cycle.

If you are noticing these patterns, see our complete guide on warning signs your concrete needs professional attention.

How to Fix Rising Concrete

The approach to fixing heaved concrete depends on the cause and severity.

Option 1: Address the Root Cause First

Before any physical repair, you need to stop whatever is pushing the slab up.

For frost heave: Improve drainage around the slab. Extend downspouts. Ensure grading slopes away from the concrete. A well-drained gravel base under the slab prevents ice lens formation.
For clay expansion: Manage moisture levels around the foundation. Consistent watering (not over-watering) can prevent the extreme swell-shrink cycles that cause damage.
For tree roots: Install a root barrier, prune the offending roots, or in severe cases, remove the tree. We cover this in detail here.
For hydrostatic pressure: Install French drains, sump systems, or channel drains to redirect subsurface water.

Option 2: Concrete Leveling (Grinding or Injection)

Once the cause is addressed, the uneven surface still needs correction.

For minor heaving (less than half an inch): Concrete grinding can shave down the high spots to create a flush surface. This works well for sidewalk trip hazards caused by root pressure.

For moderate heaving: If the slab has risen significantly but is still in good condition, it may settle back partially once the cause is removed (especially with frost heave). Monitoring through one full seasonal cycle before leveling is sometimes the wisest approach.

For uneven settlement after heaving: Once a heaved slab settles back down, it often does not return to perfectly level. The surrounding slabs may have also shifted. This is where concrete leveling comes in, injecting material beneath the low areas to bring everything back to a uniform plane.

To understand how the leveling process works step by step, see our guide on how concrete leveling works.

Option 3: Replacement

If the heaving has shattered the slab into multiple pieces, or if the root damage is too extensive, replacement may be the best option. When replacing, the contractor should address the underlying cause at the same time, by installing a proper gravel base, root barriers, or drainage improvements before pouring the new slab.

Prevention: Keeping Your Concrete Flat

The best repair is the one you never need. Here are the most effective prevention strategies for Colorado Springs homeowners.

Drainage Management

Action	Why It Helps	Cost Range
Extend downspouts 6 to 10 feet	Keeps concentrated water away from slab edges	$10 to $50 per spout
Correct grading	Prevents water from pooling under concrete	$500 to $2,000
Install French drain	Redirects subsurface water before it causes pressure	$1,500 to $5,000
Seal control joints	Stops surface water from entering the base	$2 to $5 per linear foot

Tree and Landscaping Management

Plant new trees at least 10 feet from any concrete surface (20 feet for aggressive species).
Install root barriers at the time of planting. It costs $5 to $15 per linear foot now versus thousands in concrete repair later.
Avoid over-watering near concrete edges. Drip irrigation aimed at plant beds 3 feet from the slab is safer than sprinklers that saturate the base.

Seasonal Maintenance

Fall: Clear debris from control joints. Seal any open cracks before winter. Ensure gutters are clear. See our full winter concrete protection guide.
Spring: Inspect slabs for movement after the thaw. Look for new cracks or changes in elevation. Address drainage issues before the summer rain season.
Summer: Manage irrigation to prevent over-saturating clay soils. Keep consistent moisture levels rather than alternating between soaked and bone dry.

The Bottom Line

Concrete rising is not a mystery. It is the predictable result of forces pushing upward from below, whether that force is freezing water, swelling clay, growing roots, or trapped moisture.

In Colorado Springs, where the soil is reactive and the freeze-thaw cycle is relentless, heaving is something every homeowner should understand and watch for.

The good news is that most heaving damage can be corrected without tearing everything out. Identifying the cause, addressing it, and then leveling the affected slabs is typically the most effective and affordable path forward.

If your concrete is rising, cracking, or creating uneven surfaces, contact us for a free assessment. We will identify what is causing the movement and recommend the right solution for your specific situation.

What Causes Concrete to Rise? Understanding Frost Heave and Slab Heaving in Colorado