Ask a foundation contractor what causes the most damage in mid-Missouri, and you will usually hear two words: clay and water. Clay soil holds moisture, swells when it gets wet and shrinks when it dries. Water that stays close to the foundation adds pressure to the walls, soaks the ground under the slabs and finds its way into basements and crawl spaces. Together they explain a large share of the cracks, bowing walls and sloping floors we see.
How clay soil moves
Clay particles are very fine and can hold a lot of water between them. When the soil is wet, it expands and pushes outward. When the soil dries, it contracts and pulls away. In a long dry summer, the soil next to a house can shrink enough to open a gap under a slab or along a footing. Then a heavy rain can cause it to swell and push back. Repeated over many years, that cycle moves the foundation a little each time.
This movement is not always even. The soil on the sunny side of a house dries faster than the soil on the shady side. A downspout that dumps water in one spot keeps that patch wet while the rest of the yard dries. A tree near one corner pulls more moisture from the ground there. Uneven soil moisture is what creates uneven settlement.
Where water usually gets in
Water rarely enters a foundation in one dramatic moment. It usually builds up slowly from a few common sources:
- Downspouts that end at the wall, or in a short extension that drains right back toward the foundation.
- Grading that slopes toward the house instead of away from it.
- Gutters that are clogged, sagging or overflowing at the corners.
- Cracks and joints in the wall, especially at the top of block walls and where the wall meets the slab.
- Window wells and patios that collect water and drain toward the foundation.
Check your own drainage
You can learn a great deal about your drainage with an hour of walking around the house. On a day after rain, look at the following:
- Where the water goes when the downspouts discharge. Is it several feet from the wall, or right at the foundation?
- Whether the soil next to the house slopes away from the wall. A good rule is that the ground should drop a few inches over the first several feet.
- Whether water stands in the yard, in a low spot near the house or along the side of the driveway.
- Whether the basement or crawl space has damp patches, a white powder on the walls or a musty smell.
Simple fixes are often the best place to start. Extend the downspouts at least several feet from the house, clean the gutters, and add soil to low spots next to the foundation so the ground slopes away from the walls.
When a French drain makes sense
A French drain is a trench filled with gravel and a perforated pipe that carries water away underground. It is useful when water collects around the foundation even after the surface drainage has been corrected, or when a yard holds water in the same place every time it rains. The trench is sloped so the water flows out to a safe outlet, away from the house.
Installing a French drain disturbs the yard, so it should be planned carefully. We survey the site, check where the water is coming from, and explain the route, depth and restoration before any digging starts.
When a sump system is needed
A sump system collects water in a pit under the basement floor and pumps it out. It is used when water collects under the basement or when gravity drainage cannot carry the water away from the house. A sump system needs power and a reliable outlet, and it needs regular checks to make sure the pump works when it is needed. We explain whether a sump is the right choice before recommending one.
Crawl spaces need their own moisture control
Crawl spaces get the same clay and water as basements, but they are easier to forget. Damp soil under the house raises the moisture in the framing, invites insects and leads to rot in the joists and beams. A vapor barrier laid across the ground, with proper ventilation and support for the framing, keeps the space drier and protects the wood above.
Protect the foundation in the long run
Once the water is under control, a few habits keep the foundation stable. Keep the gutters clean. Check the downspout extensions after heavy rain. Water the foundation evenly during long dry spells, since drying soil causes almost as much movement as wet soil. Plant large trees away from the house and keep shrubs trimmed back from the walls.
If you see damp patches, a white powder on the walls or cracks that appear after rain, it is a good time for a drainage check. See our waterproofing and drainage service for the options we use, or read about crawl space repair if the damp is under the house. Either way, a written plan with a price comes before any work begins.
Want a second opinion on your drainage? Contact the foundation repair in Columbia, MO team and we will walk the property with you.