Freeze-Thaw and Your Foundation: What a Missouri Winter Does

West Central Missouri sits in a rough middle zone. We don't stay frozen all winter like the northern states, and we don't stay mild like the Gulf. Instead the ground freezes, thaws, refreezes and thaws again, sometimes several times in a few weeks. Each cycle moves the soil a little.

The City of Warrensburg's residential code adoption puts our frost line at 36 inches and rates weathering here as "Severe," with an air freezing index of 1017 (City of Warrensburg code adoption, Table R301.2(1)). In plain terms, frost can reach about three feet down, and concrete and masonry here take a beating from repeated freezing and thawing. Footings are meant to sit below that frost line for exactly this reason. The trouble usually starts in the soil and water above and around them.

Water expands when it freezes. When the soil next to your foundation is saturated, that water turns to ice and the ground swells upward and outward. Clay holds water longer than sandy soil, so it stays wet going into a cold snap, and wet clay that freezes can push hard against a basement wall, lift a stoop or a slab edge, or nudge a shallow pier in a crawl space.

Then it thaws. The ice melts, the soil loses volume and settles back, but rarely to the exact spot it started. Over a winter of cycles, that push and drop can open cracks, tip a step away from the house or leave a low spot that holds water next spring.

Our area has plenty of that kind of clay. Based on USDA soil survey data, roughly four in ten acres of rated soil in Johnson County are classed as high shrink-swell, with most of the rest moderate. That's a county-scale estimate, not a reading on any one lot, and you can look up the soils under your own address on the USDA NRCS Web Soil Survey. Soils in Pettis and Henry counties run more toward moderate, but there's still enough clay around Sedalia, Clinton and the farms in between to matter.

The single biggest winter problem we see isn't the cold itself. It's water being dumped right at the foundation wall just before a freeze.

Think about a typical December week. Snow sits on the roof, the sun comes out, and meltwater runs into gutters that may already be full of leaves. If the downspout ends a foot from the house, or the gutter overflows, all of that water soaks into the clay right against the wall. That night it freezes. Now you have the wettest, most expansive soil on the property sitting exactly where it can do the most harm.

Ice dams and frozen downspouts make it worse. When a downspout freezes solid, water backs up and spills over the gutter, straight down along the foundation. We see the results in spring as staining on basement walls, wet spots in crawl spaces and cracks that line up suspiciously well with a downspout.

Freeze damage tends to hide until the ground lets go. While the soil is frozen, everything is held tight. Once it thaws, a few things happen at once. The soil near the surface turns soft and saturated. Snowmelt and early spring rain add more water on top. And any gaps, cracks or loosened joints opened up over the winter give that water a path inside.

That's why March and April are when people find a new crack, notice a floor that slopes a little more or see water in a basement that stayed dry all fall. If you do find something after the thaw, take a photo, put a date on it and watch whether it changes. A hairline crack that stays put is a different story from one that's widening or letting in water. If you're not sure which you're looking at, that's what a free inspection is for.

The good news is that most winter damage comes back to water, and water is something you can do a lot about in the fall. We always look at the water first, because a repair on a house that still has water problems usually doesn't hold up.

Here's where we'd put the effort before winter sets in:

• Grading. The soil next to your house should fall away from it, not toward it. Over time, flower beds get built up, backfill settles and patios sink, and the slope reverses. If water pools along the foundation after a rain, it will pool there before a freeze, too. Getting the yard to drain away is the most important fix on this list, and it's the core of our Drainage Correction & Grading work.
• Downspout extensions. Get roof water well away from the house. MU Extension recommends extenders that carry water "10 feet out and downhill" (MU Extension, First aid for leaky basements). Make sure they aren't pointed at a neighbor's foundation or into a low spot that drains right back.
• Clean gutters. Leaves that fall in October are exactly what clogs gutters in December. A clean gutter and a clear downspout are the cheapest freeze protection there is.
• Crawl space vents set up for your space. There isn't one right answer for every crawl space. Some do better with vents closed and the space sealed, others need them working. What matters is that the crawl space stays as dry as possible going into winter, without cold, wet air sitting on the framing all season.
• Fill soil gaps. After a dry late summer, clay can pull away from the foundation and leave a gap. MU Extension's advice, as reported by Ozarks Farm & Neighbor, is to check for those gaps "before soil freezes or spring rains hit" (Ozarks Farm & Neighbor). A gap along the wall is a funnel for meltwater.

If you want a full seasonal list of what to check, we keep one here: our seasonal foundation maintenance checklist. This post is about why the fall items matter so much; the checklist covers the rest of the year.

Not every crack needs a contractor, and plenty of fall projects are things a homeowner can handle with a shovel and a couple of downspout extensions. We'll tell you straight when something can wait.

It's worth having someone look before the ground freezes if you see any of these:

• Cracks that have grown since last year, or that are wider at one end than the other
• Water standing against the foundation after an ordinary rain
• A basement or crawl space that was wet last spring
• Doors or windows that started sticking after last winter
• A stoop, step or slab edge that has tipped toward or away from the house

Fall is a good time to sort out drainage, because the work can be done before the ground is frozen and wet. We work across Warrensburg and the surrounding towns, from older neighborhoods near the square and UCM out to newer subdivisions, and you can read more about how we handle homes in town on our Warrensburg service area page. Whatever we find, you'll get a written estimate before any work starts, and nothing to sign on the spot.

If winter left its mark last year or you'd rather not find out this spring, request a free inspection or call us at (816) 718-3385.