Expansive Soil and Basement Water in Colorado Springs

Updated October 7, 2026 · 5 min read

What expansive soil is

Swelling soils contain clay minerals that take up water and expand. The most notorious is montmorillonite, the main mineral in what builders call bentonite. The Colorado Geological Survey has long noted that the Front Range is underlain, at least in part, by swelling soils and swelling shales, and research along the Front Range has tied damage to houses and streets to bentonite beds in the Pierre Shale and nearby formations.

Our semi-arid climate makes the problem worse. Soil here spends long stretches dry, then gets soaked by spring snowmelt, a monsoon storm, or a lawn sprinkler. Each swing from dry to wet and back makes the ground heave and settle. A house sitting on top of that feels it.

How it lets water in

Foundation cracks

Swelling soil pushes against basement walls and lifts slabs. Over years, that pressure opens cracks in poured concrete walls and gaps where the slab meets the wall. Water that collects in the soil outside follows those cracks inside.

Slab heave

Basement floors that are not structurally tied to the walls can rise when the soil under them swells. In many Front Range homes built on swelling soil, the basement slab floats on purpose so it can move without lifting the house. That movement can crack the slab and shift interior walls built on top of it.

Water held against the wall

Clay drains slowly. Once it is saturated, water sits against the foundation instead of soaking away. Backfill next to the house, which is often looser than the native soil, can act like a moat and hold water right where you do not want it.

Window wells

A window well is a hole dug through that backfill. It catches snowmelt and storm runoff and can fill like a bucket if the drain at the bottom is clogged or missing. Our post on window well flooding covers covers, drains and what to do when one overflows.

Cracks worth watching

Mark the ends of cracks with a pencil and the date. If they grow, that is useful information for an engineer and for any restoration crew drying the basement.

Grading: the first fix

The ground right next to the house should fall away from it. The International Residential Code, which local building departments use as a base, calls for at least 6 inches of fall within the first 10 feet from the foundation where the lot allows. Over time, backfill settles and the slope can reverse, so water runs toward the wall instead.

• Look at the ground after a rain. If water puddles near the house, the grade needs work.
• Rebuild low spots with compacted soil, not mulch or gravel alone.
• Keep the top of the soil several inches below siding and window well tops.
• Do not plant thirsty shrubs or flower beds right against the foundation.

The Colorado Geological Survey publishes homeowner guides on landscaping and maintenance for homes on swelling soil, and they are worth reading if your lot has a history of movement.

Downspouts and sprinklers

One roof can shed a large volume of water in a single storm, and all of it comes out of a few downspouts. If those downspouts empty right at the foundation, you are pouring water onto the exact spot that swells.

• Add extensions so water discharges several feet away from the house, onto ground that slopes away.
• Keep gutters clear. Overflowing gutters dump water straight down along the wall. Hail can also crush gutters, which our post on hail damage and roof leaks covers.
• Aim sprinkler heads away from the walls and window wells. A sprinkler soaking the foundation every morning keeps the clay wet all summer.
• Check for leaking irrigation lines near the house, especially after the system starts up in spring.

Neighborhoods where this comes up

Swelling soil is not limited to one part of town, so the right question is what your own lot sits on. A soils report from when the house was built, if you can get it from the builder or seller, often says. On the east side, in places like Banning Lewis Ranch and Falcon, and in parts of Security-Widefield, many homes have finished basements, which turns a small seep into a bigger cleanup. Many newer subdivisions were built with foundation drains and underdrain systems to manage groundwater. Our post on sump pump and underdrain problems explains how those work.

When water gets in

If you find water on the basement floor:

1. Figure out whether it came from outside or from plumbing. Water along an exterior wall after rain or melt points outside.
2. Photograph it, and note the weather in the days before.
3. Pull up area rugs and move boxes off the floor.
4. Get extraction and drying started. Even a small amount under carpet and behind finished walls can lead to mold in a cool basement. See basement flooding for what the crew usually does.

Most homeowners policies exclude groundwater seepage and earth movement. That makes prevention outside the house more valuable than any claim. A restoration crew can dry the space and tell you where they think the water came from, and a structural engineer or drainage contractor can handle the fix.

Sources and official resources

• Contractor license lookup (Pikes Peak Regional Building Department)
• Homeowners insurance help (Colorado Division of Insurance)
• IICRC: restoration industry standards body
• Flood insurance basics (FEMA FloodSmart)
• A Brief Guide to Mold, Moisture and Your Home (EPA)
• Colorado Springs weather warnings (National Weather Service, Pueblo)