Finishing Your Basement

Leaking Cove Joints: How To Protect Your Basement From Groundwater

If you notice mold growth on the walls in your bathroom, kitchen or laundry room, you may wonder if you have leaking water in your home. But after checking the rooms thoroughly, you can't find any signs of leaking water. One of the places you should look for leaking water is along the flooring and walls of your basement. You may have stress fractures and deteriorated concrete along the basement's cove joints. Here's how cove joints damage over time and how you can protect your basement from leaking groundwater.

What Are Cove Joints?

Cove joints are the areas that connect the basement's walls to its flooring. The joints support or brace the walls so that they don't collapse or crack from the stress placed on them by the upper floors of your home. Sometimes, the cove joints weaken from age or foundation stress, which allows groundwater to spill, seep or flow into the room. The water attracts mold spores that eventually travel through your heating and cooling system to the rest of the home.

Groundwater comes from rain, local ponds, lakes, and other bodies of water. The water flows deep within the soil beneath your property and is comprised of rocks, sediments and other natural elements. Groundwater becomes a problem for your basement when the soil around your structure weakens or erodes. Soil erosion endangers your home, because it can sink into the ground over time.

As the house sinks, stress fractures develop along the cove joints. The water beneath the ground travels up toward the surface of your property. If it rains or snow melts on the ground, the water in the ground increases until it soaks into your basement's foundation.

One of the things you want to do is repair or seal the cove joints. By sealing the joints, you strengthen and reinforce the walls and flooring of the basement. You also build a barrier between the cove joints and ground that stops groundwater from entering the room.

How Do You Keep Groundwater Out of the Basement?

You can repair the joints with mastic sealant yourself. Mastic sealant forms a waterproof barrier around the leaking cove joints. In addition, the sealant fills in missing or damaged concrete, which prevents groundwater from entering your basement. 

Here's how you use mastic sealant effectively in your basement:

  • Place a container of mastic sealant inside a caulk gun.
  • Sweep and clean the area around the cove joints to remove cobwebs, dust, and dirt. Place at least two carpet blower fans in the basement to dry the flooring and walls thoroughly. You don't want water to flow back onto the joints during your repairs.
  • Wash and dry the walls with a disinfectant soap and cool water if you spot signs of mold. Mold can still grow in the basement, even after you seal it.
  • Seal the cove joints of each wall, even if you don't see damage or leaking water. Water can travel around the basement's foundation until it finds a small hole or crack to pass through.
  • Give the sealant at least 72 hours to dry completely. If you notice water leaking from the repaired cove joints after you sealed them, apply several more layers of sealant to reinforce the joints.

After you repair the cove joints, contact a contractor to install an exterior drain tile system near the basement to direct groundwater away from the basement, as well as brace or reinforce the walls of the basement with steel beams and concrete to prevent problems with your cove joints in the future.

Some DIY sites offer tips on how to brace your basement's walls yourself. However, you should avoid doing so. If you install materials in the wrong sizes or strengths, the walls can collapse. A contractor will calculate the correct materials to use for your basement's walls before beginning the work.

If you have additional concerns about your leaking basement, schedule an appointment with your foundation contractor immediately or visit sites like