Water seeping into your basement can be alarming. You may notice puddles on the floor, moisture building up on walls and pipes, or a musty smell. Water infiltration needs to be addressed quickly to prevent damage to your home’s foundation and structure. Understanding the source of the water is the first step to remedy the issue.

Common Causes of Water Infiltration In Basements

There are several potential causes of water coming up through a basement floor:

High Water Table

The water table refers to the level of groundwater below the surface. If the water table rises close to your home’s foundation, it can begin to seep into the basement through cracks and pores in the concrete. A high water table is often seasonal when snow melts or after heavy rains. In some areas, the water table is naturally higher. Installing an interior or exterior drainage system can help lower the water table around your home’s perimeter.

Landscaping Issues

Improper grading or landscaping that slopes towards the house can channel water towards the foundation. Planting beds, planters, or yards that don’t slope away from the home allow the soil to become saturated. Ensuring at least a 6-12 inch grade slope away from the house for the first 10 feet helps prevent water from pooling near the foundation.

Leaking Water Lines

Cracks or damage to water supply lines, drain pipes, or sewer lines inside or outside the home can leak water into the surrounding soil and saturate the ground. This water will drain downwards into the basement. Inspecting all plumbing lines around the home can identify leaks that need repair.

Clogged Gutters and Downspouts

When gutters become clogged with debris, water can overflow and drain along the foundation. Downspouts that empty too close to the home’s perimeter can also contribute to saturated soil. Regular gutter cleaning and redirecting downspout extensions further from the house helps prevent this.

Foundation Cracks

Small cracks in the concrete foundation or where the wall meets the floor slab can allow water to seep in from the soil outside. These cracks expand over time due to pressure, settlement, earthquakes, etc. Sealing cracks from the interior or exterior side of walls with hydraulic cement blocks this moisture entry route.

Poor Surface Drainage

Hard surfaces like patios, walkways, or driveways sloped towards the house channel rainwater and snowmelt towards the foundation. Regrading these surfaces to slope away from the home and installing drainage systems helps divert this water away from the basement.

Signs of Water Infiltration In Basements

Some common signs that moisture is infiltrating the basement include:

Puddles or damp spots on the floor along walls or under windows. Look for moisture in corners especially after heavy rains.
Dark stains on the floor, walls, or ceiling from chronic dampness. Mold or mildew may start growing in persistently wet areas.
Flaking or bubbling paint where moisture is drawn through the walls or seeping in through cracks.
A musty, damp smell that seems stronger near the floor and exterior walls.
Condensation building up where cooler walls meet warmer, more humid interior air, especially on pipes and vents.
Crumbling, cracking, or shifting of foundation walls or floors from chronic water pressure and damage.
Failing waterproofing or old drainage pipes causing leaks near the interior footer drains or exterior foundation drain tiles.

Dangers of Water Infiltration In Basements

While a small amount of seepage may not immediately damage your home, over time chronic moisture can cause many problems. Untreated infiltration leads to:

Wood decay and damage – Wet framing, sills, joists, and subfloors will eventually warp and rot, compromising structural integrity.
Mold growth – Mold feeds on the excess moisture, spreading quickly on organic materials like drywall, framing, and insulation. Mold contributes to poor indoor air quality and is difficult to eradicate fully.
Insect and pest infestation – Termites, carpenter ants, and other pests are drawn to moist wood.
Indoor air quality issues – Excess moisture enables the growth of mold, mildew, and bacteria which circulate through the home via HVAC ductwork.
Foundation cracking or shifting – Chronic water pressure and freeze/thaw cycles can expand cracks and destabilize the structural integrity of the basement over time.
Flooding – Extreme cases may result in extensive flooding during heavy rains if exterior drain tiles become clogged or overwhelmed.

Preventing excess moisture in your home’s basement is key to protecting not just your belongings stored downstairs but the entire structure from deterioration.

How to Diagnose the Source of Basement Water Problems

Determining why and where water is infiltrating into your basement takes some sleuthing. Here are steps to diagnose the issue:

Inspect After Heavy Rains

Aim to inspect the basement walls and floor during or immediately following heavy rains when seepage is actively occurring. Identify where moisture appears or collects to pinpoint entry sources. Trace damp areas back to potential entry points.

Look For Cracks and Leaks

Thoroughly examine the interior walls, corners, and slab perimeter for cracks, damage, or Subtle leaks allowing water through. Probe any cracks with a screwdriver to determine if they extend deeper into the wall or foundation. Also inspect exterior foundation walls for similar cracks.

Check Surface Drainage

Head outside after rains and see where water flows and collects around the perimeter, especially near entryways, patios, landscaping, and driveways. Improper drainage sloping towards the house could cause seepage.

Inspect Gutters and Downspouts

Confirm that gutters are clear of debris so rainwater can flow freely. Downspouts should aim water several feet away from the home’s foundation using splash blocks or extensions. Misaligned downspouts dump water too close to the basement walls.

Evaluate Landscaping and Grading

Adequate slope should prevent the soil and turf around the home’s perimeter from becoming saturated. Check grades slope 1⁄4 inch per foot within 10 feet of the walls. Also ensure plantings are not too close to the foundation.

Consider Plumbing Leaks

Inspect water lines, drain pipes, indoor sink basins, and appliances for slow leaks that could drip water into the subfloor. Confirm exterior hose spigots are sealed properly. Even small leaks over time can lead to water seepage.

Hire a Professional Inspector

A drainage contractor or basement waterproofing expert can conduct a thorough investigation of both interior and exterior conditions leading to your water infiltration issues and recommend appropriate solutions.

How to Stop Water from Coming Up Through Basement Floor

Once you’ve determined the entry points, here are several ways to address water seepage through the basement floor:

Improve Exterior Grading and Drainage

Installing a drainage system helps capture rainwater from gutters, lawn areas, and hardscapes to prevent it from pooling near your foundation. Options include French drains, catch basins, sump pumps, or dry creek beds to divert water away from the house. Proper grading is also key.

Repair Foundation Cracks

Use hydraulic cement to seal narrow cracks in poured concrete walls and floors that allow water to seep through. Epoxy injection seals wider gaps or cracks in block wall foundations. Removing interior or exterior wall sheathing may be required to access cracks for repairs.

Apply Basement Waterproofing Sealer

Special waterproofing paints or sealants create a protective barrier between damp concrete and the interior space when applied on basement walls and floors. Look for products like Drylok or RadonSeal specifically made for basement waterproofing.

Install Exterior Foundation Drainage

An underground perforated pipe system collects groundwater from the exterior perimeter of footers and pumps it away from the home to lower the water table. Adding new exterior drain tiles along the foundation diverts seepage before it enters your basement.

Repair Leaky Plumbing

Fix any cracks or faulty joints in supply lines, drain pipes, and sewer lines that are leaking water near or under the basement slab. Preventive step like replacing older galvanized pipe helps avoid leaks.

Install Sump Pump System

Interior sump pits with pumps provide backup protection even with exterior drainage. The pumps discharge water away from your home’s foundation collected in the pit from perimeter drain tiles or the basement slab.

Frequently Asked Questions

What are signs of a high water table?

Signs of a high water table allowing seepage into your basement include water accumulation after rains, chronic dampness along lower walls, and water consistently trickling or weeping through foundation cracks especially during wet seasons.

How can I tell if gutters are causing basement flooding?

Check gutters after heavy rains – water overflowing instead of flowing through clear downspouts indicates they are clogged with debris. Also look for sections pulling away from the home or sagging from weight of the water. Downspouts should aim water several feet from the foundation.

What slope should the ground around my house have?

Ideally the grade should slope 1/4 inch per foot away from the home for at least the first 10 feet perimeter around the foundation. This ensures adequate drainage without creating an excessive slope. Drainage swales can help direct water away.

What could cause musty basement smells?

A persistent musty, damp smell usually means moisture is infiltrating and providing an environment for mold, mildew and bacterial growth. Run a dehumidifier, address any leaks or cracks allowing seepage, and clean any affected areas to remedy musty odors.

How do I identify plumbing leaks near my foundation?

Inspect water supply lines, drain pipes, waste vent stacks, and all water fixtures both inside and outside your home for cracks and leaks. Condensation on pipes may indicate cold groundwater cooling warm interior air, signaling a leak. In unfinished areas, look for water stains under pipes and joints.

What is the best way to seal concrete foundation cracks?

For narrow hairline cracks, use hydraulic cement that expands as it cures for a watertight seal. Epoxy injection seals will fill wider gaps and cracks by injecting high-strength epoxy resin into the space. Both approaches work for interior basement cracks or exterior foundation cracks.

Can I waterproof my basement from the inside?

Yes, interior basement waterproofing is an option using waterproofing paints and coatings on the concrete surfaces. Look for products designed for basements below grade, not just damp concrete sealers. The coating creates a protective barrier between the foundation and interior space, minimizing moisture transfer.

How much does professional basement waterproofing cost?

Depending on the size of your basement and severity of water infiltration, costs typically range from $2,000 to $10,000. Extensive projects involving excavating for exterior drainage systems, sump pumps, and foundation repairs will be higher. Get quotes from at least 3 contractors.

Conclusion

Left unchecked, water seepage and high moisture levels in your basement can eventually compromise your home’s foundation and structure. Catching and correcting water infiltration issues early is important to prevent extensive damage and necessary repairs down the road. Inspect the interior and exterior perimeter of your foundation walls and floors to pinpoint where water is entering after heavy rains. Address areas of poor drainage or improper grading around the home that contribute to a high water table. Repair cracks or leaks in your foundation and plumbing lines that allow water through. Improve surface drainage. And consider installing a waterproofing paint coating and sump pump as proactive measures against basement flooding, even after addressing the initial leaks. With some diligent sleuthing and DIY repairs or professional waterproofing services, you can remedy ongoing water seepage through basement floors for a dry, healthy interior space.

Why Water Is Coming Up Through Your Basement Floor—and How to Fix It