Posted on: 29.06.2023 Posted by: Редакция Comments: 0

Water seeping through a concrete floor can be a serious problem. It can not only cause damage to items stored on the floor, but the resulting moisture can lead to mold and other issues. What is the best way to stop seepage?

To prevent water from seeping through a concrete floor, you need to determine where it is coming from. Water can seep through excessive hydrostatic pressure or structural issues in the concrete, and sealing may not solve the problem. Finally, check if the issue is caused by seepage and not condensation.

Concrete floors in a garage or basement should not be wet, and excessive moisture penetrating through concrete can damage them, so you need to isolate the problem and take appropriate measures. Keep reading to learn more.

What Causes Water to Seep through Concrete?

Waterproof materials include plastics, metals, and glass. Concrete, on the other hand, allows water to penetrate through. The evaporation of water during the curing process allows for the formation of air voids and veins in the concrete, enabling water to penetrate through the concrete.

Water can seep through concrete due to an imbalance in relative humidity. The direction in which moisture moves is determined by the moisture in the concrete and in the air. So, if the concrete has a higher relative humidity than the surrounding air, it releases moisture into the air.

It also absorbs moisture when the relative humidity of the ambient air is higher.

Moisture can also seep through concrete due to hydrostatic pressure or the pressure water exerts on objects and surfaces. In general, the deeper the foundation, the more susceptible the basement concrete floor is to water seepage problems. Below are the most common reasons for water seeping into a basement.

  • Your house is located on a slope, and water runs down to your house.
  • The house was built at or above the water table.
  • Water cannot drain from the ground due to a high clay content.

Don’t be fooled, thinking that your concrete is not damaged when it dries out. Both moisture content and movement can damage it, and you need to take the necessary steps to prevent this.

Signs that Hydrostatic Pressure is Causing Water Seepage

If you live in an area with frequent and heavy rainfall, and your house is located on a slope, hydrostatic pressure naturally increases. Diversion techniques, which will be discussed later, could be helpful.

However, if your house is built on flat land, there are other signs that indicate you may be dealing with hydrostatic pressure:

  • Standing water in your yard, indicating saturated soil.
  • Water seeping into the bottom of a 2 to 4-foot-deep trench or hole in the ground.
  • If water is seeping into your basement, it is coming from multiple directions.
  • The soil does not have visible cracks.
  • Your neighbors are experiencing similar issues.

If water is seeping through your basement floor and you seal it, the simple solution may lead to additional problems unless you take steps to reduce pressure. Here are a few suggestions.

Check Your Gutters

Gutters are designed to divert water away from a house. However, clogged gutters can cause water to run down the side of a house and against the foundation. In the worst case, gutters can detach from the fascia, allowing water to enter your house and cause damage to roof rafters and walls.

Add extensions to the gutter system. Flexible extensions give you more control over how you divert water away from your house.

Install a French Drain

French drains relieve a foundation by directing water away from a house and replacing the compacted soil around the foundation.

A French drain consists of an underground perforated pipe surrounded by gravel or small stones. The trench should start where hydrostatic pressure is strongest, and then slope downwards away from your house.

How deep the trench needs to be excavated depends on whether the water pressure on the drain is due to a hill or your basement being below the water table.

If the drain is experiencing excessive water pressure from a hill, the trench may be shallow. However, a French drain will need to be dug deeper if the issue is due to a high water table.

Installing a French drain is something a homeowner can do, but it can be time-consuming and requires digging trenches. You can rent a mechanical excavator for deeper channels or consider hiring professionals.

Inspect Your Landscaping

The ground around your house should slope away from it. So, first, check the slope of the property.

  • Shrub and flower beds near a house tend to slope, so the ground needs to be built up. The ground should slope 2.5 cm per foot away from the foundation.
  • If a lawn has not been properly leveled, it may need to be regraded. However, this requires a lot of soil and heavy equipment and is best left to landscaping specialists.
  • The soil could also be compacted or contain excessive clay. Adding organic material to clay soil can help, but improving drainage in clay soil through organic material is a slow process.

Before you regrade a lawn or modify clay soil, install a French drain and see if it removes enough hydrostatic pressure.

Check for Underground Erosion

Use a hammer to lightly tap on the concrete slab where you discover moisture. A slight echo could indicate that you have a void chamber beneath the slab, and the weight of the concrete has caused a crack.

Water seeping through cracks in concrete

How to Prevent Water from Seeping through a Concrete Floor

If you have concluded that the cause is not hydrostatic, then fixing water seepage will require several steps.

  • Cracks and joints need to be repaired. Use a concrete repair kit for the cracks and a cold seam sealer for the joints.
  • Test the amount of moisture in the concrete using a calcium chloride test, available at hardware stores or online.
  • Use the test results to decide what type of waterproof floor sealant to use.

Your Concrete Floor Could Be Sweating

It is possible that the water is not seeping through the concrete but that your floor is “sweating.” A damp concrete floor can be caused by condensation from warmer, humid air coming into contact with the concrete, just like the outside of a glass sweats on a hot day.

For this to happen, the concrete floor must be colder than the air. The air could be cooled to the same temperature as the concrete, which is most common in areas with cold winters in the springtime.

In addition, salt is hygroscopic, meaning it attracts water. Therefore, salt deposits on concrete can draw moisture from the air onto the concrete. If you live in an area where the roads are salted in the winter, you may be bringing salt into the garage, and this salt removes moisture from the concrete.

Sweating is less likely on a concrete slab in a house, but it does occur. Here are the conditions under which this can happen:

  • The ground is colder than the dew point temperature of the air, and warm, humid air is entering the house.
  • A concrete floor with high moisture content has a highly cooled surface.
  • There may be no vapor barrier underneath the slab.
  • An elastic floor covering like vinyl flooring can exhibit extremely high moisture levels.

These can be due to a concrete slab being framed before it cures or not having a vapor retarder beneath it.

However, you should not ignore this problem. A sweating concrete floor can lead to mold or, worse, alkali-silica reaction caused by the alkali hydroxides used in cement paste, a condition known as “concrete cancer.” Consult a concrete expert to address this situation before your slab is permanently damaged.

Sweating can also occur on the floor of a basement, which happens in the summer when warm and humid air enters the basement. As the air cools, water condenses and lands on the concrete.

Testing for Sweating

If you lift a box or mat and the bottom is dry while the rest of the floor is wet, sweating or condensation could be the cause.

To determine if your concrete is wet due to sweating, use the following test:

  1. Wait for the concrete to dry out.
  2. Cut a square piece of plastic sheeting measuring 16 x 16 inches.
  3. Tape it tightly to the garage floor, sealing all four sides to ensure no gaps of air.
  4. Allow it to sit until your concrete appears wet.

If your concrete appears wet, remove the plastic. Your floor is sweating if the concrete beneath the plastic is dry. However, if you find moisture beneath the plastic, water is seeping through your floor.

How to Fix a Sweating Floor

To stop a sweating floor, you need to address the causes of the floor sweating. This may include one or more of these steps.

  • Use a dehumidifier to remove moisture from the air. For a dehumidifier to work, doors and windows must be closed.
  • Improve circulation above the floor. A fan directed at the floor prevents the air from resting long enough to condense.


Before attempting to fix the problem, determine its cause so that you can select a solution that fixes it without causing additional issues. Once you have narrowed down the problem, decide if you can fix it yourself or if you should consult an expert.

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