Water Coming Up Through the Basement Floor: Why It Happens

Why does water come up through a basement floor?

Many basements have perforated drain pipe around the foundation that carries groundwater to a sump, where a pump sends it outside (SDSU Extension). When that system is missing, plugged, crushed or poorly installed, water builds up around the foundation and is more likely to come in through the walls, the floor, or the joint between them (SDSU Extension).

If the water table stays above the floor, water will keep finding ways in for as long as it stays high (NDSU Extension). Heavy rain and poor drainage add to it. In a 1-inch rain, about 1,250 gallons of water fall on the roof of a 2,000-square-foot house (University of Minnesota Extension).

Is it groundwater, a drain backup or condensation?

• Seeping along the bottom of the wall and through floor cracks, and it keeps coming: groundwater (NDSU Extension).
• Coming up out of the floor drain: that's a drain or sewer backup, a different problem with different fixes. See basement floor drain backing up.
• Damp floor and walls in summer, with the windows open: warm, humid outdoor air condenses on cool basement surfaces. Many homeowners mistake this for a leak (University of Minnesota Extension).
• A damp ring at the base of the walls: moisture wicks up through small pores in the concrete footing and slab. It's very common at the joints where concrete was poured at different times (University of Minnesota Extension).
• Water in one spot in dry weather: rule out a plumbing leak under the slab. If your water meter moves when nothing in the house is running, call a plumber.

What should you do right now?

1. Don't go into a flooded basement unless you know the electricity is off (Nebraska Extension).
2. Take photos before you start, for insurance (Nebraska Extension).
3. Move water to the floor drain, or use a wet vac or pump (NDSU Extension).
4. If the basement is deeply flooded, don't pump it all out at once. Pressure from water in the soil outside can crack the walls and floor if the inside is drained too fast. Pump the level down 2 to 3 feet, mark it, and check the next day. If it rose back over the mark, wait and repeat (Nebraska Extension).
5. Never run a gas-powered pump or generator indoors. The exhaust contains deadly carbon monoxide (Nebraska Extension).
6. Check the sump pump. If it isn't working, water builds up in the sump and the basement can flood (SDSU Extension).
7. Get carpet, boxes and other porous items off the wet floor (NDSU Extension), and start drying within 24 to 48 hours to prevent mold (EPA).

Can you seal the floor from inside?

Usually not for good. Water generally can't be stopped with products applied inside the basement because of the water pressure outside. The goal is to control where the water goes, not to block it (NDSU Extension).

Cracks are normal in concrete foundations, and drainage usually removes the water that comes through them, though some may need repair (University of Minnesota Extension).

What fixes it, in what order?

University of Minnesota Extension recommends starting with the easy, low-cost steps and working up (University of Minnesota Extension):

1. Cut indoor moisture sources and vent the dryer and bathroom outside.
2. In summer, don't ventilate the basement with warm, humid outdoor air.
3. Fix grading, gutters and downspouts. Soil should slope away from the foundation at least 1 inch per foot for at least 6 feet. Downspout extensions should discharge at least 4 feet from the wall. This step may solve the problem on its own.
4. Add an interior or exterior drainage system if water still gets in.

• Exterior drainage means digging up around the foundation. It's the most costly approach but also the most effective (University of Minnesota Extension).
• Interior drainage is the usual choice when water is already coming in. The most effective version is perforated pipe under the edge of the slab, inside the footing, connected to a sump (University of Minnesota Extension).
• A channel glued along the base of the wall is the simplest and least costly option, but it can't drain groundwater from under the slab (University of Minnesota Extension).

Where should the sump pump discharge?

• Not into the city sewer. It can overload the system and cause sewage backups in neighbors' basements, and many cities prohibit it (SDSU Extension).
• Not onto a septic drain field, a neighbor's lot or into window wells (SDSU Extension).
• At least 20 feet from the house if possible, so the water doesn't soak back down to the foundation and get pumped out again in a loop (SDSU Extension).
• Cover the sump. The pit should have an airtight, childproof cover (University of Minnesota Extension).

Is the water clean, and will insurance cover it?

Groundwater seepage is typically treated as Category 2, or gray water, under guidelines adapted from the IICRC standard (University of Colorado Anschutz guidelines). Wear gloves and boots and keep kids and pets out.

Seepage through the foundation is typically excluded from standard homeowners policies (Amica). Sump pump overflow usually needs a separate water backup endorsement (Insurance Information Institute). See does homeowners insurance cover water damage?

Common questions

Related guides

• Water in the basement after rain 6 min
• Basement floor drain backing up 5 min
• Does insurance cover water damage? 7 min

Local water damage help

Each state page lists the towns we cover, with local shut-off and sewer numbers and flood notes.

• Water damage help in Georgia
• Water damage help in Texas
• Water damage help in Missouri
• Water damage help in Colorado
• Water damage help in Tennessee
• Water damage help in Massachusetts
• Water damage help in Utah
• Water damage help in Minnesota
• Water damage help in Idaho
• Water damage help in Washington

Town pages that cover this problem, with local water and sewer numbers:

• Arlington, GA
• China Spring, TX
• Black Jack, MO
• Beech Bluff, TN
• Acushnet Center, MA
• Marriott-Slaterville, UT
• Albany, MN
• Hauser, ID