How To Waterproof Basement Walls From The Inside

Last Updated on February 8, 2022 by Kimberly Crawford

Basements are built lower than the surface level of your home, and this means that they are more likely to deal with water than the rest of your home. 

Have you ever been in your basement and noticed a wet patch on the walls, flooding, paint peeling from the walls, or even rotted wood? Water can damage your belongings, damage the basement itself and even cause a health hazard, so you can see why so many people want to add a waterproofing method. Leak detection is the first step. Once you’ve found the leak, it is time to take action, and this can include installing a dehumidifier, or more effectively, waterproofing the walls from the inside. 

When a home is built, there will be a plan for waterproofing, but over time the house may develop issues such as cracks, or absorbing water that has built up in the soil outside. This can lead to a humid or damp basement.

What Is Waterproofing?

basement wall leak

Waterproofing can come in many forms. It is basically the practice of preventing water from getting into the home and causing damage. Waterproofing treatments can involve both the inside and the outside of the house.

It could be structural, like making changes to the actual foundations and building of the house, or it could be a way to treat the walls on the inside and fix cracks so that water is not able to enter the basement.

Related: Basement Leaks Where The Wall Meets The Floor

Should I Waterproof My Basement From the Inside or Outside?

Both. Exterior waterproofing can make a really big difference. In some cases, it might be necessary to stop the flow of moisture from getting into your basement, but it can be a big undertaking. 

When a home is built, the builder will have taken steps to ensure that water can’t get in, but over time this can fade. To redo the exterior waterproofing, you will need to fully excavate around the house, add a waterproof membrane and improve the drainage system, and even add pumps in some scenarios.

In areas that are prone to prolonged rain or heavy storms, this is even more crucial. 

However, exterior waterproofing might not be required, and it is possible that the interior work can be more than enough. The two have to work in harmony. Many steps can be taken to waterproof the basement walls and ensure that nothing gets in. 

The Dos and Don’ts of Waterproofing Basement Walls

Basements are an essential part of many homes, and basements used as living space add more than 50% to the value of a house. Unfortunately, stained and musty basement walls can be a major turn-off for potential buyers. Sadly, even the best waterproofing system cannot stop some water from penetrating through concrete blocks and cement mortar.

Waterproofing basements is both an art and a science due to the many components that make up this kind of construction. The best waterproofing contractors are experienced in either concrete or block walls. Concrete block has the advantage of being much more stable than concrete, and concrete block walls can be much thicker than concrete walls, which will allow for greater drainage. However, concrete is very strong and much less expensive to build with.

How do you know which type of waterproofing system will work best for your basement? It all depends upon the layout and design of the exterior walls and floor, as well as how much water penetration you currently have from the exterior.

In order to prevent further damage, a full inspection for all problems is necessary before any waterproofing can begin. In most cases, this means you will need to pay a contractor twice: once for the inspection and once for the actual waterproofing job. If you choose to do it yourself, which is seldom recommended, remember to get all necessary permits before beginning any work.

Your plan of attack should depend upon the current water penetration in your basement walls. There are basically three ways it can happen: 1) direct through the walls or 2) through cracks at the floor or 3) no water penetration in the basement at all.   

If the basement has no water penetration, then it is the simplest situation. All that is required are two coats of waterproofing paint for interior walls or a tube of premixed latex patching material for exterior walls.

If there are only cracks at the floor level, then leveling these floors will cure the problem. However, if there are any cracks in the basement walls that are more than 1/8″ wide, more extensive work will be needed.

If the problem is direct penetration through the walls, all of these methods can be combined to create one plan of attack. Remember, you cannot patch before sealing the exterior wall; the waterproofing paint or material must seal against air and water tightness.

When sealing, don’t just fill the crack with paint or material and think that you have stopped any water penetration. Repairing even small cracks can make a big difference in how well your basement walls will resist water. Once the outside is repaired, it should be painted thoroughly for maximum effectiveness. It’s also important to check for other possible causes of water penetration. Look for any gaps around pipes or wires that enter the exterior wall through holes in the concrete block, which will make waterproofing more difficult and require a flexible material such as latex caulk to fill in these large cracks.

Brick walls are generally not repaired; they need to be replaced with new blocks that have been treated correctly for water resistance. If this is not an option, you can use the same methods for repairing concrete block walls.

Common Causes of Water Filling in Your Basement

Unfortunately, there are a lot of causes of water getting into your basement. Some of the common issues include:

  • Cracks in foundation and walls. Unfortunately, it is possible for parts of your home to develop cracks over time and this can lead to water entering the premises.
  • Overflowing gutters. If your guttering system isn’t up to the task then it can cause a buildup of water and erosion within the soil around your basement, meaning a lot of water is putting pressure on the exterior walls.
  • Downspouts and discharge problems. You need to make sure your downspout extends far enough from your house to discharge the water.
  • Pavement cracks. If your home has a lot of pavement nearby then it is possible that this is causing rainwater to find its way into the basement.
  • Clogged windows or poor-quality basement windows. Of course, windows can prove to be an entry point into your basement for water, so if the windows are getting a bit old and starting to crack you might end up with water pooling.
  • Roof leaks. Water coming from the very top of your home can seep all the way down and cause basement problems.
  • Internal leaks. Plumbing leaks in the house shouldn’t be ruled out. While it is easy to assume the water is coming from outside, it is possible that it is coming from appliances.
  • Inadequate drainage. This is a crucial part of the design of your home, drainage should take water away from the basement.

A Step By Step Guide On How to Waterproof Basement Walls from the Inside

If you are able to detect leaks and make changes from the inside rather than go through the huge upheaval of exterior work, then the steps below can stem the flow of water and help you to ensure a safe and secure basement for years to come.

Clean Up the Area

Cleaning up the area will let you properly examine and determine where any water is coming from, as well as spot other issues in your home and basement that you might miss in a dirty or cluttered basement. Try to move appliances and other items into the center of the room if you think that the water is coming from the outside. 

A lot of the waterproofing products you will be applying need to go onto walls without any coverage, so if you have any coatings you will also need to clear these away before starting.

Determine the Source of Water

This is probably the most important step. Working out where the water is coming from. Fortunately, there are often some telltale signs that show you where the water or moisture is coming from.

Assuming your basement is walled with concrete, you may be able to see streaks of where the water is entering, which can be around cracks, pipes, supply lines, or even the sewer pipe. If the water is confined to one specific area then it might be a sign that you can tackle the issue by fixing one particular crack or leakage.

If the whole of the wall feels wet and clammy then you can investigate further. One of the best tips is to dry out a full area of the wall, and then put a square piece of foil on the wall, sticking it in place and keeping it there for 24 hours. When you remove it, if the underside of the foil is wet, you can be pretty sure that there is water coming in from inside. If it is dry then it could be an internal issue, that can potentially be fixed with a dehumidifier or a steam outlet.

Fill Up Any Cracks or Gaps

Cracks and gaps are the ultimate enemies of your basement! You need it to be a secure space so that even if there is water pooling outside (not ideal) it doesn’t have an easy route in. 

If you do see any cracks it is time to fill them with concrete. Sounds like a big job, but any competent DIYer can do this. 

You need to use hydraulic cement that can be bought from a hardware store. It mixes with water, and you can use gloves or a knife (never bare hands) to mix it and push it within the cracks. It is designed to expand so it will fill the space and make it totally watertight.

Cracks can appear as the house settles in place having been built, so it isn’t uncommon to see these within a year or two of a brand new home being built. 

Apply Waterproofing Products to the Walls

There are many great waterproofing products you can add to your walls once you’ve fixed any cracks and leaks. These can help to secure your basement for the long term. 

Waterproof products include:

  • Concrete coatings, are usually thick and applied with a hard and heavy brush. They can only be applied to bare concrete but these are affordable and great for concrete and masonry walls. They come as a dry mix and you add water to them.
  • Silicate sealers or densifiers are also only suitable for unsealed and unpainted walls. They actually react with the concrete or bricks that made the basement wall, making them harder and more waterproof.
  • Specific waterproof paint could be a good option, and it needs to be applied very liberally when you are decorating with it. Remember that the other treatments can’t be added after you have painted. Once it has dried and cured, that is going to be it. 

Upgrade Gutters and Downspouts

Gutters and downspouts can collect water and guide it away from your home, preventing pooling and effectively stopping the water at the source, so you can worry a bit less about what can enter your home. One effective way to stop water from getting in is to get a quote for improved gutters and downspouts as well as check whether there are leaks or damage in your guttering system.

How Much Does It Cost to Waterproof a Basement?

Basements are among the most common areas for water intrusion. Water penetration can lead to mold growth, structural damage, and costly cleanups. The good news is that waterproofing a basement is relatively inexpensive compared to the cost of repairing or replacing one.

The cost to waterproof a basement varies greatly by region, depending on several factors including climate zone, whether the soil is sand or clay, and how many footings must be waterproofed. On average, cost to waterproof a basement runs $3-$5 per square foot for basement walls. This includes materials and labor.

Costs can go up if sump pumps are installed to pump out water that gets into the basement wall cavities. Costs can also increase if a weeping tile system is used instead of the traditional French drain. A weeping tile system may be required in areas with clay soil or tight basements that don’t allow for proper water drainage.


Is there such thing as waterproofing a basement with zero maintenance?

The average basement will require some amount of waterproofing maintenance. You can expect your basement to require less maintenance as the years go by and everything settles into place, but you’ll still need to monitor it at least once a year for cracks and leaks. How frequently you’ll need to monitor depends on several factors including soil conditions, how much rain falls, whether you have weeping tiles or not, etc.

Is there any way to test how waterproof my basement is before I commit to a full-on project?

The best way to see if your current system is working properly is before you invest in new materials and labor by testing for leaks! A pressure test of the exterior wall can be completed by a professional in an afternoon. If the pressure test doesn’t reveal any leaks, you’re good to go with your current system.

If you do have leaks, don’t panic! All is not lost because there are options for waterproofing your basement that require less time and money than if you were to attempt it from the outside.

What is the difference between a french drain and a weeping tile system?

A french drain runs through the center of your basement floor and drains into an outlet or sump pump. A weeping tile system is typically used with clay soil instead of sandy soil. Instead of draining to an outlet, water from both the inside and outside walls will drain out to a perimeter drain.

Should you seal interior basement walls?

Experts will vary, but most will agree that sealing the interior walls is not necessary to get a good result from basement waterproofing. In fact, it’s best to leave them unsealed so moisture can escape easily.

Interior basement wall sealing should only be done if you have concrete surfaces inside your basement and there are no cracks or openings for water to pass through.

How long does waterproofing a basement take? Full-scale exterior projects can take 2-4 weeks depending on the size of your home and the specific project that’s being done. Interior systems typically take less time, but can be longer if more than one technique is required.

What steps should you follow after installation?

As with any home improvement project, you should have a professional grade moisture barrier installed after your waterproofing system to avoid water infiltration.

Should I Drylock my basement walls?

DryLok is a sealant that ‘locks in’ the moisture in your basement. Most experts don’t recommend this product because it doesn’t allow water to escape if there are any leaks in your basement wall system.

What waterproofing products do you recommend?

If you’re looking for exterior systems, we recommend Guardhouse Waterproofing. They’re a national company and use some of the most advanced waterproofing techniques available today. For interior systems, we recommend Interior Drainage Systems Inc. They’ve been servicing the Greater Toronto Area’s basement drainage needs for more than 20 years!


Waterproofing basement walls from the inside is a far more simple job than having to alter the foundations and get a lot of work done to the actual structure of your house. Some of the solutions are actually very affordable and can be done yourself without the help of a professional, which can save you a lot of money in the long run and even help to protect your health, as mold and dampness are bad for you and can easily build up in the basement if it isn’t up to standard or springs a leak.