Many basement leaks in Olathe are seepage through the wall, not a broken pipe. The clay soil under much of Johnson County shrinks in a dry August and swells when it takes on water in spring. Its low permeability keeps water pressed against the foundation, so a basement that stayed dry all summer can start weeping in March.
Key takeaways
- The mapped Grundy silt loam under much of Johnson County is a deep, fine, smectitic clay formed in loess, and it drains poorly.
- Smectitic clay shrinks when it dries in late summer and swells when it wets, which opens cracks and gaps beside the foundation.
- Water moves slowly through this clay, so it can build up against a basement wall in a wet spring and seep in at the joints.
- A wall leak usually shows up as damp lines, efflorescence or water at the floor edge, while a burst pipe leaves a single fast source you can find and shut off.
- The August 2017 storms dropped 5 to 7 inches of rain in about six hours in the Kansas City metro, a reminder that heavy summer rain can reach basements too.
- Before any repair work starts, the cleanup crew should dry the wall cavity and the floor, and anyone doing structural or plumbing repairs should be licensed through Johnson County Contractor Licensing.
What kind of soil is under Olathe?
Much of Johnson County sits on a deep silt loam called Grundy, formed from windblown loess and dominated by smectitic clay. Clay like this holds a lot of water and passes it slowly. That combination is the starting point for most seepage problems on the Kansas side of the Kansas City metro.
The soil series description for Grundy silt loam describes a very deep soil that is somewhat poorly drained. Its subsoil is fine and smectitic, with a dense layer where the clay content runs from roughly 42 to 48 percent. Water moves through that layer very slowly, which is why the soil feels heavy and sticky after a rain and why it does not dry out quickly in spring.
Most homes in the post-1980 subdivisions were built with the foundation cut into this soil. The crew that backfilled the wall was working with the same clay that was dug out, so the material next to the basement is usually the same dense, slow-draining soil that sits further out. Knowing that helps explain why a wall can stay wet long after the rain has stopped.
Why does clay shrink in August and swell in spring?
Smectitic clay changes volume with its moisture content. When it dries it pulls away from surfaces, and when it wets it expands and pushes back. Those cycles act on a foundation every year, and they are most visible at the edges of the house where the soil and the wall meet.
In a dry late summer the soil around the house can shrink enough to open gaps between the backfill and the wall, and to widen hairline cracks in the concrete. The gap at the top of the wall, near the grade, is often the first place water finds. A downspout that has been dumping water right beside the house can make this worse, because the clay directly under it stays wet while the rest of the yard dries.
When the spring rains come, the same clay takes on water and swells. The expansion squeezes the backfill and can push against the wall, and it fills the gaps that opened in August. Because the clay drains so slowly, the swollen soil can stay saturated for days or weeks. This cycle explains why a basement can look fine in July and show seepage in March, even though nothing about the house has changed.
How does a wet spring turn into a wall leak?
The clay drains slowly, so water collects above the rock or dense layers and forms a perched saturated zone during wet years. That zone can rise to within about one to three feet of the surface. When it reaches the level of the basement wall, water pushes through the joints, cracks and cold seams.
Soil scientists describe this as a perched water table: water sitting in a layer of soil above a less permeable layer. In the wettest years the saturated zone for Grundy soil can reach within about 0.3 to 1.0 meters of the surface. A basement that is set into that zone is effectively sitting in a pool, and the wall takes the pressure.
The leak often follows a pattern. The first sign is usually damp lines at the bottom of the wall, a white crust called efflorescence where the concrete is wet, or a smell of musty air along the outside corner. Water may appear at the floor edge where the wall meets the slab, and in a finished basement it can soak the bottom of the drywall first. These signs build over several days of rain, which is different from the sudden flooding of a burst line.
How do you tell seepage from a burst pipe or sewer backup?
Seepage tends to appear slowly, along walls or at the floor edge, and it is worse after a long wet period. A burst pipe usually produces a steady or sudden source you can trace and shut off. A sewer backup comes up through a floor drain or lower fixtures and carries a different level of contamination.
Start by looking at where the water is. If it is tracing down a wall, pooling along the joint between the wall and the floor, or showing up in several places after a rain, seepage is the likely cause. If you can see a stream from a fitting, a stain spreading across the ceiling below a bathroom, or water that stops when you close a valve, the source is plumbing. Check the water heater, washing machine hoses and ice-maker line as well.
A sewer backup is a separate problem. It typically comes up through the floor drain or a lower-level toilet or shower, often during heavy rain, and it is treated as contaminated water. Johnson County Wastewater is the sanitary sewer provider across the county, and it says the sewer lateral from a house to the public line is normally the owner's responsibility. If you are not sure which of the three you are dealing with, treat the water as possibly contaminated and call for help before you start moving things.
What did the 2017 floods teach about basements?
The National Weather Service recorded heavy flooding along local creeks in July and August 2017. The August event brought 5 to 7 inches of rain in roughly six hours, with some spots reporting 8 to nearly 10 inches. Indian Creek at State Line Road rose to about 28 feet, a record for that gauge.
The Weather Service summaries for 26 to 27 July and 21 to 22 August 2017 describe catastrophic flooding along local streams and record crests on Indian Creek and Tomahawk Creek. Those events were mostly about creeks and overland flow, not about foundations. Still, the same heavy rain saturated the clay around houses and overwhelmed storm drains, which pushed water toward basement walls and floor drains.
Creeks such as Indian, Tomahawk, Cedar and Kill Creek drain much of the county, and their flooding raises groundwater in nearby neighborhoods. A basement that is not in a mapped floodplain can still take water through the wall during a heavy summer storm. Homeowners should check their own address on the official floodplain map and not assume that being away from the creek means being safe.
What should you do in the first hour?
Close the main water shut-off if you can reach it safely, and keep out of standing water near the electrical panel, the furnace or any basement outlet. Treat anything that came up a floor drain as contaminated, and keep children and pets away from it. Then photograph the damage before anything is moved.
Water near electrical equipment is the first hazard. If the basement is standing in water, do not walk into it to reach the panel. Shut off power at the main if you can do it from a dry location, or call the electric utility. Do not run the sump pump through standing water if its wiring is exposed.
Next, take photos and video of the walls, floor, ceiling and any wet items, including the water line on the wall if there is one. Call your insurer early and ask what documentation it needs. Coverage is decided by your insurer under your own policy, and the Kansas Insurance Department notes that many standard homeowners policies exclude sewer backup and flood water unless an endorsement or separate policy applies. A technician can document moisture readings and photos for your claim, but the insurer decides what is covered.
What does drying and cleanup involve?
Drying starts with removing standing water, then setting air movers and dehumidifiers and checking moisture readings until materials are dry. Wet materials that cannot be dried, such as soaked carpet pad or swollen drywall, are removed. The emergency stage is explained and approved before the work begins.
A crew typically uses moisture meters and thermal imaging to find water hidden behind drywall, under flooring and inside wall cavities, because surface dryness can be misleading. Materials are dried in place where possible. Where a wall has been soaked from the bottom, the crew may cut out the lowest section of drywall so the cavity can dry and be checked.
EPA guidance says mold can begin to grow on wet wood, drywall, carpet and furniture within about 24 hours, and that water-damaged areas should be dried within 24 to 48 hours. That is why drying begins as soon as a crew can reach the property. Repairs after drying are quoted separately, once someone has seen the wet area. The price for the emergency stage is confirmed on site before any work begins.
What should you check before repairs start?
Look up any contractor in Johnson County Contractor Licensing's online search before work begins, especially for plumbing, electrical, mechanical or roofing. Plumbing repairs, sewer lateral work and any structural or waterproofing contract should go to a licensed trade. Mold remediation has no state license in Kansas, so ask what industry guidance the crew follows.
Johnson County Contractor Licensing covers the participating cities across the county, including Olathe, and it lists eleven license classes. Plumbing, electrical, mechanical and roofing contractors must be licensed with the county. Its online search shows whether a company is licensed and allowed to do the work. Check your address with the city or county building department if you are unsure which office applies.
Kansas does not license mold remediation the way some states do, and the Kansas Department of Health and Environment says it does not regulate mold in homes. Ask what industry standards the crew follows, such as the ANSI/IICRC S520 mold remediation standard, and what certifications its technicians hold. Some foundation work, including waterproofing contracts, is outside the scope of drying and cleanup, so get separate quotes for that from a qualified contractor.
Frequently asked questions
Why does my Olathe basement wall leak only in spring?
The clay soil around many Johnson County foundations swells when it takes on water in spring and holds that water for a long time. That pressure pushes through the joints and cracks that opened during the dry late summer. The same wall can stay dry in July because the soil has shrunk and drained away from it.
Is wall seepage the same as a burst pipe?
No. Seepage usually shows up slowly along the wall or at the floor edge and gets worse after several days of rain. A burst pipe typically gives a steady or sudden source you can trace and shut off. If you cannot tell which it is, shut off the water at the main and call for help.
What is a perched water table, and why does it matter for my basement?
A perched water table is water that collects in a layer of soil above a less permeable layer and cannot drain quickly. In the wettest years the saturated zone for Grundy soil can reach within about 0.3 to 1.0 meters of the surface. If your basement wall sits inside that zone, it can take water through the wall even when no pipe has failed.
Will my homeowners insurance pay for seepage or sewer backup?
Coverage depends on your own policy, and only your insurer can decide it. The Kansas Insurance Department says many standard homeowners policies exclude sewer backup and flood water, and that this coverage normally needs an endorsement. Ask your agent early, and keep photos and records of the damage. A crew can give you moisture readings and photos for the claim.
How quickly does the cleanup need to start?
Start as soon as it is safe to do so. EPA guidance says mold can grow on wet materials within about 24 hours and that water-damaged areas should be dried within 24 to 48 hours. A crew is dispatched as fast as one is available, and the phone line is answered 24/7. Drying is the part that cannot wait.
When do the first freezes usually come to Kansas City?
The National Weather Service puts the average last spring freeze for Kansas City around early April, and the average first fall freeze around late October. Those are averages, and actual dates vary from year to year and from place to place. Freezing matters for pipes, but for foundation seepage the bigger driver is wet spring soil.
Sources
- National Weather Service, Kansas City/Pleasant Hill
- National Weather Service, Kansas City/Pleasant Hill
- Wikipedia
- U.S. Census Bureau
This guide is general information for Johnson County homeowners, not a substitute for an on-site inspection. Prices are estimates. See our disclaimer.