Window well caving in: why the soil is winning and what replacement costs in Fort Collins

A window well that is caving in, bowing toward the window, or filling with soil from behind has lost the fight with the ground around it. On the Front Range that ground is expansive clay, and the shell was never going to win. The fix is replacement at $1,100 to $3,300, with the well set in a drained gravel column instead of native clay so the new one stays put. Caught early, while the shell is still true and only the backfill is moving, a re-set with drainage runs $350 to $1,100.

Check this first (five minutes, a tape and a straightedge)

1. Measure the projection. Window face to well wall at the tightest point. Code wants 36 inches. A well that started at 36 and now reads 32 has bowed four inches and is no longer a compliant egress well.
2. Lay a straightedge across the rim. A round or rectangular well whose rim has gone oval or has a flat spot has yielded.
3. Look for soil in the well. Clay on the gravel, or a cone of dirt against the back wall, means the shell has opened a gap somewhere and the backfill is coming through.
4. Check the flange and anchors. A shell that has pulled off the wall on one side is being pushed by the soil on the other. The heaving well page covers that version.
5. Push the steel with a screwdriver at the soil line. Bowed and rusted is a different quote than bowed and sound, though both usually end in replacement.
6. Look for water sources. Sprinklers, a downspout, a bed that gets watered. Wet clay is what pushes.

What is usually wrong

Why this happens in Fort Collins

The Colorado Geological Survey defines expansive soil as clay-bearing soil that “expands to a significant degree upon wetting and shrinks upon drying,” and says the bentonite and montmorillonite clays that “underlie many populated areas of Colorado” can “expand up to 20% by volume when exposed to water and exert a force of up to 30,000 pounds-per-square-foot.” Its map of the Fort Collins quadrangle puts the city over the Pierre Shale and lists swelling and collapsing soils over that shale as one of the two most common natural hazards in the area. The survey’s heaving bedrock page adds that the hazard “is responsible for tens of millions of dollars worth of damage along the Front Range piedmont of Colorado.”

A corrugated well is a thin steel ring buried in that soil, usually backfilled with the same clay that came out of the hole. The Nunn series, the USDA soil with its type location in Larimer County near the Harmony School, is smectitic clay, the shrink-swell family. Every wet spring the clay swells and pushes on the shell; every dry summer it shrinks, opens a crack, and the next storm fills the crack with more clay. The ring takes a little more set each cycle. Rust at the soil line speeds it up. Eventually the well is oval, then it is caving.

CSU Extension’s guidance for homes on these soils is the prevention: limit landscaping along the foundation to non-irrigated mulch and xeric plants, avoid trees next to the foundation, and direct roof drainage away. A well surrounded by a sprinklered flower bed is a well in wet clay.

What replacement includes

Excavate the old well and the swollen clay behind it. Replace that clay with clean, washed rock and filter fabric, so the shell sits in a drained column that does not change volume when it rains. Tie the column into the foundation drain where the house has one, which the city’s egress guide requires for new wells. Set a well sized to code, 36 inches of projection and 9 square feet, anchored into sound concrete. Add the ladder if the well is deeper than 44 inches, which on a 30-inch frost line most bedroom wells are. Grade the surface away from the house, extend the downspout, move the sprinklers, and fit a cover. For a deep well on a sloped lot, or one that will be seen from a finished bedroom, a composite terraced well or an engineered kit is stiffer than light-gauge steel and worth the difference. For a shallow well in front of a utility room, galvanized steel with a real gravel bed is the right spend.

When to call

If the projection has dropped below 36 inches on a bedroom well, if soil is coming through, or if the window frame has cracked, send the form with a photo from above and the projection measurement. The well cost calculator prices replacement by depth and material before we talk. We replace failed wells across Fort Collins, Loveland, Windsor, and Timnath, and the expansive soil post explains why the drainage column is the part of the quote you should not let anyone cut.