Practical Guide To Sealing Basement Walls

In this guide, we will be discussing all you need to know about sealing your basement walls.

Waterproofing Basement Walls From Inside

When water invades your basement, it likely does so through the spaces in your basement walls. These spaces could be the pores in your poured concrete or cracks in the walls.

Either way, they are excellent passages for water to creep in and do some serious damage to your structure and property.

For this reason, sealing basement walls should be taken seriously. Thankfully, it isn’t a hard task to accomplish, and you can do it all by yourself.

Why You Should Seal Your Basement Walls

The answer to this question seems pretty straightforward, however, it goes deeper than preventing water from penetrating the walls.

That’s indeed the main purpose of sealing the walls, but here are some of the consequences you will have to face if your basement walls aren’t properly sealed.

Damage to your structure: When water keeps seeping through the foundation walls and into your basement, the wall will begin to weaken over time.

Since the wall sits right by the foundation, being weak may spell doom for the rest of the home, as there is an increased chance of a collapse.

Devaluation of your property: A basement wall that has suffered significant water damage over time will not impress potential buyers when they come to inspect your house.

In fact, the prospect may lose interest altogether. Even if they still express interest in buying, it would be at a price that is way below your original asking price.

The reason for this is obvious – The new owner will have to pay for the fixes after the home purchase has been completed.

Mold and efflorescence growth: Besides compromising the strength of your structure, leaking basement walls also means mold growth.

As you may already know, mold thrives on wet surfaces, especially when these surfaces are in dark, warm areas. Your basement is one of such environments, and a leaking basement wall will be ideal for mold spores to land and grow.

Mold is known to cause allergies to humans when they make contact with it. To add to that, people with asthma and other respiratory problems can have their conditions worsened if they come in contact with mold.

Efflorescence can also begin to appear when your walls leak. Just like mold, it too thrives on damp surfaces. Although it isn’t harmful to human health, it reduces the aesthetic appeal of your basement.

How To Seal Basement Walls

Now that you understand why it is important to seal your basement walls, let’s take a look at how you can do it all by yourself!

Step one: Remove the water before you begin sealing

In a case where the leaks in your basement wall have caused flooding, it is advised that you first remove the water before you begin sealing.

This is the best thing you can do, as standing water may make it hard to locate the source of the leak. That aside, standing water is dangerous if the electricity is on.

Cut off the power in the basement, then go in and remove the standing water before you take the next step.

Step two: Find the source of water

You can’t begin sealing your basement walls without first identifying the leak. This could either be one or more cracks in the wall itself or by the cove joints.

Careful observation is all you need to spot the source. Move away from any furniture by the leaking wall so you can have a better view.

Check for water drip marks and use them to trace the cracks. The drip marks typically start from where the cracks are.

Once you have identified the cracks, you can move on to the next step.

Step three: Prepare the surface

Obstacles will not allow you to seal your basement walls properly so you should get rid of them first.

Remove any furniture that blocks the wall cracks so you can have more workspace. You should also use a brush to clean off any debris that’s stuck in-between the cracks.

Some quick swipes will remove chips, dust, and spider webs, and this will create a better surface for the cement to adhere to.

Step four: Seal the cracks with hydraulic cement

Hydraulic cement is great at fixing both interior and exterior cracks in your basement walls. They come in a powdery form but quickly turn into a putty-like substance when mixed with water to form a trustworthy sealant.

To use hydraulic cement, mix a portion of the material with some water (as recommended by the manufacturer), then use a spade to scoop up a desired amount of the mixture and paste it deep into the cracks.

The good thing about hydraulic cement is that it expands in the spaces, so it makes them water-tight.

You can apply another layer of the mixture if the first one was insufficient. Be sure to level the plaster with the wall’s surface, just so the patch blends in with the rest of the wall.

Step five: Apply to finish

Now that you are done sealing the wall cracks with hydraulic cement, it would be nice if you gave it a smooth finish, just so your basement will maintain its beauty.

While using regular paint is a good idea, waterproofing paint is much better.

The good news is, the latter also comes in several colors to match the already-existing color of your basement walls. Not to mention the fact that it is thicker than regular paint and it stops seeping water from making it to the inner surface of your basement wall.

If you’ve never used waterproof paint, then keep reading, as I’ll be discussing it next!

Applying Waterproofing Paint

Cracks in walls aren’t the only cause of wet basements. As hard as concrete walls are, they are also very porous.

Indeed, you can’t see the pores, but these microscopic passageways are present, and they provide the spaces for tiny droplets of water to seep onto the interior wall surface.

To be sure water is seeping through the pores in your basement walls, you can do a simple foil test. This will involve taping a piece of foil paper on your basement wall and leaving it there for a few days.

Take off the foil and inspect the part that rested on the wall to see if it has collected any moisture. You will find droplets on it if it has.

Going by the results of the foil test, it would be wise to waterproof the inner parts of the wall, and waterproof paint is ideal for this job.

There are different makers of waterproof paint, but the rules of application are pretty much the same.

Here’s what you need to do to seal your basement walls with waterproof paint.

Step one: Clear the surface

Remember, waterproof paint is meant to sink into the pores of your concrete basement walls and solidify within, making it impossible for water to pass through and settle on the surface.

But this will be impossible if there are other forms of matter on the walls, as the waterproof paint will be unable to pass through the blockages.

Therefore, you must first clean the surface of the walls before applying the waterproofing paint.

Remove any mold growth or efflorescence build-up and scrape off the old paint so that the concrete wall and its pores will be fully exposed.

Step two: Apply the paint

Now that the concrete wall is bare, you can begin applying the waterproof paint. You can use a paintbrush or a roller for this task.

For the first layer, dip the roller into the paint bucket and spread the content across the wall. Leave no area untouched as you paint, you can use the brush to paint over tight corners that the roller can’t access.

You can stop painting when you’re sure you’ve covered the entire wall.

Step three: Leave the paint to dry, apply another coating if need be

Leave the first layer of waterproof paint for a few hours to dry, then take a look at the wall to see how much of the paint sunk into it. If the surface paint looks faded, then you can apply another coating over it for reinforcement.

Be sure to spread the second coating evenly across the wall so you’d have a beautiful finish. Remember to use the roller to paint over the wider spaces, and the brush to paint over the hard-to-reach areas.


Sealing your basement walls from the interior and exterior is something you can do all by yourself. Just follow the tips provided in this article.

However, if you’re not up for it or simply don’t have the time, then you can call a local contractor to get the job done. Although this is the more expensive option.

I trust the information provided in this article has been helpful.

Take care, and thanks for reading!

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