Expansive Soil and Concrete in Colorado Springs: What Homeowners Should Know

Quick answer

Much of the Colorado Springs area sits on clay that swells when wet and shrinks when dry, which can lift slabs (heave) or let them drop. The most effective protection is controlling water: grade away from the house, keep sprinklers and downspouts off slab edges and seal joints. New slabs benefit from careful subgrade work; heaved panels usually need grinding or replacement, not lifting.

Last updated October 22, 2026

If you've lived in Colorado Springs for a while, you've probably seen it: a sidewalk panel that has tilted up, a patio that now slopes toward the house, a garage floor with a crack running down the middle that's higher on one side. Often the cause isn't bad concrete. It's the ground under it. This guide explains what's going on and what homeowners can do about it.

What expansive soil is

Expansive soils contain clay minerals that absorb water and swell, then shrink as they dry. The Colorado Geological Survey identifies montmorillonite, often loosely called bentonite, as the clay mineral generally responsible. CSU Extension notes that all of Colorado's major population centers are partly built on expansive soils, and that swelling soils damage thousands of homes each year.

For Colorado Springs specifically, a Colorado Geological Survey seminar paper describes clay soils in the Colorado Springs and Pueblo areas as typically expansive to some degree, and says the Pierre Shale and the claystone of the Dawson Formation can usually be expected to have moderate to very high swelling potential. Not every lot is the same: swelling potential varies from street to street, and some higher areas, like Woodland Park, sit mostly on weathered granite instead. Maps are only general; a site-specific soils test is the reliable check.

Heave versus settlement

Slabs in this region can move in two directions, and telling them apart matters because the fixes are different.

Heave: the slab or part of it rises. Signs include a panel higher than its neighbors, a patio tilting toward the house, a crack with one raised side, or a garage floor that has humped up. Heave usually means clay under the slab got wetter.
Settlement: the slab drops. Signs include a gap opening between the slab and the foundation, a walk that has sunk near the house, or a driveway that dips near the garage. Settlement often comes from loosely placed backfill compressing, from soil washing out, or from clay shrinking as it dries.

It's common to see both on the same property.

Water is the trigger

Clay doesn't swell by itself; it swells when its moisture changes. Around a house, the biggest sources of extra water are usually things homeowners control:

Downspouts that empty right next to the slab or foundation
Sprinkler heads that spray onto walks, patios and driveway edges
Lawn and flower beds watered right up against the concrete
Snow piled along slab edges that melts into the soil
Ground that slopes toward the house instead of away from it
Open joints and cracks that let water straight into the base

CSU Extension's guidance for homes on expansive soils recommends grading so water drains away from the house, keeping plantings and sprinklers back from the foundation (with trees farther out still), favoring low-water groundcovers and mulch near the house, and leaving downspout extensions in place. Those same steps protect patios and walks next to the house.

What a contractor can do for a new slab

You can't make swelling clay go away, but a new slab can be built to cope with it better:

Subgrade preparation. Removing soft or organic soil and compacting the subgrade is the baseline. On sites with highly expansive clay, some contractors or engineers recommend over-excavating and replacing part of the clay with non-expansive fill, or conditioning its moisture before the pour. Ask what they recommend for your lot.
A good aggregate base. A compacted base gives even support, but it should not become a reservoir that collects water against the clay. Drainage and grade still matter.
Slope and drainage. The finished slab should carry water away from the house and to a place where it won't soak the soil under the concrete.
Isolation joints. Separating the slab from the foundation, steps and other slabs lets each piece move on its own instead of cracking where they bind. Many garage slabs in the region are built to float independently of the foundation walls for the same reason.
Control joints and sealing. Joints at planned spacing keep shrinkage cracks tidy, and sealing joints keeps water out of the base.

None of this guarantees a slab will never move, and an honest contractor will say so. It does tilt the odds a long way in your favor.

Repairing slabs that have moved

For settled slabs: if the slab is mostly intact and sank as a unit, lifting is often worth pricing. Mudjacking pumps a cement-based slurry underneath; polyurethane foam lifting uses expanding foam through smaller holes. Fix the water problem that caused the void first.

For heaved slabs: lifting doesn't help, since the slab is already too high. A small lip can sometimes be ground down to remove a trip hazard. Larger heaves usually mean cutting out the panel, correcting drainage and possibly the subgrade, and repouring. Expect some movement to continue if the soil moisture keeps changing.

For cracks: sealing cracks and joints with a flexible sealant keeps water out and slows further damage, but it won't stop soil movement on its own.

When to call an engineer

Flatwork movement is a nuisance; foundation movement is more serious. Signs that the house itself may be moving include cracks in foundation walls, diagonal cracks at the corners of windows and doors, stair-step cracks in masonry, drywall cracks that keep reopening, and doors or windows that suddenly stick. In those cases, a structural or geotechnical engineer is the right first call, before any concrete work. Colorado's expansive soils are a well-documented cause of foundation damage, so engineers here are used to evaluating it.

Buying or building a home

If you're buying, ask whether a soils report exists for the lot or subdivision, and look at the flatwork: heaved walks and patios are clues about soil and drainage. If you're building an addition, shop or garage, the Pikes Peak Regional Building Department and your designer will tell you what soils information and foundation design are needed.

A practical checklist

Extend downspouts so water lands well away from slabs and the foundation
Adjust or move sprinkler heads that hit concrete, and use drip irrigation in beds next to slabs
Make sure soil next to the house slopes away from it
Seal open joints and cracks
Don't pile snow along the house side of patios and walks if you can avoid it
When you get quotes for new concrete, ask specifically how the contractor handles expansive soil

Need help with a heaved or sunken slab? Request a concrete contractor and include photos, ideally with a level or straightedge showing how far it has moved. You can also read about repair and leveling options.

Frequently asked questions

How do I know if my soil is expansive?

General maps from the Colorado Geological Survey show where swelling soils and bedrock are common, but conditions vary lot to lot. A soils report from a geotechnical engineer is the reliable answer, and your builder or the home's records may already include one.

Will a thicker slab or more rebar stop heaving?

Not by itself. Swelling clay can lift heavy slabs. Controlling water, preparing the subgrade and using isolation and control joints do more than extra thickness alone.

Should I stop watering near my concrete?

You don't have to stop, but keep water off the slab and out of the soil right next to it. Adjust sprinkler heads, use drip lines in nearby beds, and avoid big swings between soaking and drying.

Sources and further reading

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