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What to Do and Not Do When Waterproofing Basement Walls from Inside

renovate basement

Water that finds its way into walls and floors is the most common reason for structural damage. Repairs for a foundation damaged by water can cost up to $1,000 or more and this brings us to the importance of waterproofing basement walls from inside to keep water out.

Before you undertake the waterproofing activity, you must troubleshoot the causes. This way, you’ll be able to find the appropriate solutions. Remember that whatever approach you use to waterproofing basement walls from inside, you need to maintain the integrity of your home.

Read on to learn more!

Why Waterproof Your Basement?

Since basements are built below the ground, they tend to take on water from underground. From time to time, you’ll notice moist walls and water puddles on the floor. In the worst-case scenario, your basement may flood in the rainy season.

Humid, or damp basements can result in the growth of mold and mildew, peeling paint, or damage to stored items. While waterproofing should be done during construction, over time the walls may crack, allowing water to seep through. Even structurally sound walls may absorb water from the soil, making them feel wet.

While a dehumidifier may help remove excess humidity from the basement, the best long-term solution is waterproofing the walls. Simple do-it-yourself strategies may work, but it’s always recommendable to use the services of a professional.

Here are some tips to guide you.

1. Determine the Source of the Water

Concrete is porous, and it’s possible to see wet streaks that indicate where the water is seeping through it. Long streaks along cracks in the walls between mortar joints and around pipes could be reliable indicators. If the wall surfaces are entirely wet, further sleuthing is required.

One way to do this test is to dry an area of the wall with a rag. Attach some aluminium foil to the area and fix it with duct tape. Leave it for 24 hours and peel it to observe the underside. If it feels wet, it means your walls are seeping water from the outside.

If the foil feels dry, the source of water is likely through the floor.

2. Drain All Water From the Basement Before Repairs

During the rainy season, it’s not uncommon for the water to seep in through cracks. However, before you begin repairs, remove all water, and ensure you’re working on a dry surface. If you work on a flooded basement, you’ll increase your risk of being electrocuted.

Ensure you also turn off all power connected to the basement. Use a utility pump with a long extension cord to get rid of the water.


3. Fill Cracks with Hydraulic Cement

Cracks also commonly appear at the bottom of the basement walls. During the construction of the foundation, the footing is poured first, then the walls follow. The footing is the broad flat base made from steel and concrete to support the walls and this is the standard construction procedure, but sometimes it can lead to cracks or cold joints. Plus it can lead to the shifting and settling of a foundation along with lateral pressure from the ground.

Sealing such cracks is simple since you can fill them with hydraulic cement. The cement contains additives that cause it to expand and set in position quickly. After mixing it with water to form a dense consistency, press it into the cracks with a putty knife.

As it expands and dries, it pushes crevices and cracks to form a watertight bond. Keep in mind that it sets in within three minutes after mixing.

4. Add Dirt to Create a Slope on the Foundation

The foundation of your home should slope away from, not towards your home. If this isn’t the case with your foundation, add dirt up against the foundation to create a drop of about 2 inches. Check to see that

  • The top of the earth is approximately 6 inches below the sill plate or the horizontal piece of the building
  • Add dirt within a foot of the foundation up to a level of 2 inches
  • Ensure it’s at 15 cm below the sill plate
  • Move in increments of one foot until the slope is 2 inches per foot

With a slope, the chances of floodwater finding its way to your basement will significantly be reduced.

5. Don’t Forget the Gutters

It’s always recommendable to clean your gutters at least twice per year. The best times are in spring and fall. Start at the downspout to remove large chunks of debris. Check to see that the downspouts are about 5 feet away from your home’s foundation.

Work horizontally along the gutter to remove all the dirt. If your home lacks gutters, have them installed by a contractor. They play a significant role in diverting water away from your home.

6. Apply Masonry Waterproofing Products

If the foil test proved that water is leaking through the walls, consider exterior basement waterproofing. Use a high-quality waterproof sealant to do the job. The sealant is premixed and works just like a coat of paint.

Ensure you apply a thick coat, enough to fill all the surface holes. Allow it to dry completely before applying a second coat. It’ll form a watertight bond to keep moisture away.

7. Don’t Forget the Window Leaks

Window wells are a common source of basement leaks. They tend to retain water when the drainage system has not been constructed correctly, and this can lead to water pools around the basement window.

You can rectify this by digging about two feet lower in the well area. Fill the hole with gravel to disperse water rather than collect it in the window well. Caulk around the window to direct rainwater away.

Waterproofing Basement Walls from Inside – Take Away

If your basement is ever moist or seeps water from underground, it’s time to consider waterproofing so use this process to repair the errors responsible for the dampness. Waterproofing basement walls from inside is a process that largely depends on the cause of the moisture.

If there are cracks on the walls, for example, you can use hydraulic cement to fill the cracks. You’ll also need to work on redirecting the slope of your home away from the foundation. Do this by using dirt to increase the incline.


Don’t forget the basement window and the gutters. They can contribute to basement dampness depending on how they’re installed.

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