Is It Better To Waterproof Basement From Inside Or Outside?

what are the best basement waterproofing products (2)

It is far more effective to waterproof a basement from the outside through exterior waterproofing measures, such as installing drain tiles, excavating your soil and installing and cleaning gutters.

The term “interior waterproofing” is something of a misnomer because any steps taken in the basement’s interior are more to mitigate damage from water that has already made it through the foundation. At MJS Construction Group, we offer a wide range of duplex build.

Water is best stopped at the source — that is, it is best stopped from ever entering the concrete foundation by exterior waterproofing. However, interior waterproofing is still an important and effective step to take.

If you are wondering whether you should do your basement waterproofing inside or outside, there are many things to consider. I often visit homes where people have occasional leaks in their basement only under very heavy or unusual weather.  

These people tell me it can take a very long time before the water starts to seep into the basement, and then after the weather passes, it can continue to leak in for a while longer. Then I talk to people who, within a few minutes of almost any rain or snowmelt, they see water coming into their basement.

These two scenarios typically depict two different types of problems and can be one way to know if you should lean towards inside or outside waterproofing. Two types of water can enter your basement; surface water from rain and snow melts and groundwater that builds up underneath.

If you have a surface water problem, you will see wet basement walls that start around grade or the dirt level outside your home. If you have a negative slope towards your home from a driveway, patio, sidewalk or even sunken soil, that rain and snow will naturally run towards the home. They can wear down the original seal to your basement walls, causing dampness and cracks.  

It may be that you have taken care of all of these problems but still have chronic wet basement walls with paint peeling, mould and musty smell etc.… This means the seal to the foundation outside is not working any longer, and that water is getting into your walls. In this case, waterproofing your basement from the outside will stop the water from getting to your foundation and preserve it from further damage. It is possible to install an internal system and give you a dry space, but the condition is not stopped.

If you are experiencing the other scenario where the water comes in only along the floor at the base of the wall after prolonged weather, and your walls are mostly, if not all, dry, you are experiencing groundwater build-up under your foundation that has nowhere else to go but through the seams where the basement floor meets the walls.  

In this case, an interior basement waterproofing system will catch the water before it builds up and drains it away from your home. Often this system is called a hydrostatic relief system because it eliminates the pressure that pushes the water in through those wall floor seams.

 Waterproofing the outside, in this case, will not get the water that is building up under your floor, and you would still have seepage under those heavy conditions.

Interior vs exterior basement waterproofing, what’s the difference? What are the pros and cons? Depending on what basement waterproofing contractor or industry professional you ask, you tend to get a different answer to what method is the best and why you should use it.

I have read many articles about interior vs exterior waterproofing, but the one that stood out the most to me is this article from Integrity Waterproofing out of Lakewood. They seem to have a pretty balanced approach to basement waterproofing.

Inside Vs. Outside Waterproofing For Your Home’s Basement

What Are The Best Basement Waterproofing Products

Home basement and foundation leaks can only get worse over time, so it’s to your benefit to address such water problems immediately – but the methods of waterproofing require an expert waterproofing contractor’s skill. What follows is an overview of inside versus outside waterproofing and the processes involved, 

Interior waterproofing is done because the leaking area cannot be accessed from the exterior, likely because of restricted space. An existing water problem in your basement is not necessarily a foundation leak. Still, it might be a hydrostatic pressure problem, meaning that groundwater under the concrete rises and falls, making water penetrate the basement slab.

Some situations can’t be addressed through exterior excavation. In such cases, RCC Waterproofing employs an internal water control system, which uses an air-gap drainage membrane to direct water flow to a network of drainage tiles installed below the basement floor. The process for creating an internal drainage system is as follows:

  • The floor is broken around the perimeter in which the system is needed, about 6 to 10 inches from the foundation wall.
  • Concrete is removed, and the trench is dug to accommodate the 3-inch perforated weeping tile.
  • The weeping tile is installed and connected to a discharge such as a sump pump or a floor drain.
  • A dimpled sheet of drainage membrane is installed on the interior exposed wall where the system has been installed.
  • A layer of 3/4 inch clear gravel is installed over the weeping tile to gain maximum drainage.
  • Once the membrane and gravel are installed, any water from above or below grade will drain in the installed system.
  • A layer of concrete is then installed over the exposed trench to finish the floor back to its original level.

Exterior waterproofing is a different process and works because it eliminates the deterioration that would otherwise occur to the foundation walls. Waterproofing your basement from the exterior is recommended because the water problem is addressed directly at the source. The process for exterior waterproofing is like this:

  • Exterior waterproofing requires excavation around the perimeter of the building. The excavation depth depends on the elevation of your property. Most excavations range from 4 to 8 feet deep and approximately 2 ½ feet wide.
  • Once the hole has been excavated, speed shoring is installed to ensure the safety of the workers and prevent any soil from caving into the area dug.
  • Excavation is to the footings where the old weeping tiles are removed, and a new 4-inch weeping tile with filter cloth is installed.
  • Foundation walls are then cleaned and inspected for any voids or structural cracks. The defective areas are chiselled out and repaired with non-shrink hydraulic cement, which expands when applied to the crevices.
  • A trowel on a rubber membrane is then applied, which will be the main component to waterproofing your foundation; this product has the elongation, which will allow it to expand if any further settlement occurs in the foundation.
  • A dimpled sheet of drainage membrane is then applied, which is fastened to the top with a termination bar. This acts as a protection board and a drainage membrane.
  • Once the waterproofing and membrane have been installed, a layer of 3/4 inch clear gravel is placed over the weeping tile to maximise the drainage to its fullest potential.
  • If your home has any windows below grade and requires a window well, it is installed, and a 4-inch weeping tile is installed vertically down from the inside of the window well to the footings and filled with ¾ clear stone to create drainage in the window well.
  • Then the area is backfilled with its native soil and compacted to its original level. Once this system is completed, you have fully waterproofed your foundation and will have no further issues with water penetrating your basement.

Waterproofing a building’s foundation and the basement requires the expertise of professional, reputable waterproofing contractors. 

Interior Basement Waterproofing

Interior basement waterproofing systems are often installed as remedial solutions to clean up and address leaks and flooding that have already occurred. Typically, a trench is opened up inside your basement, parallel to the affected area. 

Then, a drainage system is installed – often a sump pump – to redirect the water out and away from your home. The trench is then sealed shut. This process will dry your basement and prevent future water intrusion. Compared to external waterproofing systems, waterproofing the inside of your home is often less costly and is most commonly used after the water has already entered the basement.

Although interior basement waterproofing is commonly called waterproofing, it is water management and not waterproofing. But to help for the sake of being consistent with what the industry calls it, we will continue to refer to internal basement water management as interior basement waterproofing.

With an interior basement, contractors allow the water pressure outside of the wall into your basement. Interior basement waterproofing will usually include a vapour barrier that isolates the basement wall and the moisture seeping through the basement wall from the air space in your basement.

Interior waterproofers will also dig a trench around the interior walls of your basement and will lay down a drainage system that channels the water to the sump pump, which will pump the water outside and away from your house. Interior basement waterproofing systems will usually include a dehumidifier as well.


  • Interior basement waterproofing is usually cheaper than exterior waterproofing.
  • In some cases, interior waterproofing is the only option due to there not being enough space between the next-door neighbour’s house.
  • Customers have reported that it works for their situation.


  • It manages a problem rather than solving the problem.

Exterior Basement Waterproofing

Exterior basement waterproofing systems typically require a more extensive and invasive installation compared to interior waterproofing. In this form of waterproofing, professionals will excavate the soils surrounding your home to expose the foundation walls. 

They will then repair or seal any small cracks or potential problems. Then, they will install a waterproofing membrane around the foundation of your home that will prevent water from ever seeping into your basement in the first place. Check out our range of Melbourne townhouse builders for your dream house.

Your foundation will be completely sealed off from the surrounding soils. Exterior basement waterproofing is typically more expensive than interior options. Still, there is virtually no price you can place on the peace of mind having a perfectly dry basement will provide you with.

Exterior waterproofing contractors dig around your foundation to the footings, fix cracks, waterproof the exterior wall with either a spray-on application or a membrane, and place a drainage system to channel the water away from your house. The water doesn’t even enter your basement. Exterior waterproofers may also install a sump pump and dehumidifier.


  • Water never enters through your basement wall.


  • It’s costly.
  • In some situations, it can’t be done due to the proximity of the buildings around.


  • Gutter installation and redirecting water runoff away from the foundation
  • Regular inspections of the foundation
  • Sump pump maintenance
  • Dehumidifier usage
  • Airflow correction

A great plus to having your basement properly waterproofed: bugs can’t get in! A crack in the foundation is a doorway to pests; sealing the cracks to avoid water damage also closes that doorway to pest intrusion.

8 Signs That You Need Basement Waterproofing

How Long Is Waterproofing Warranty

As a homeowner, there are few things more alarming than water intrusion. The structural damage that water can cause is serious, the health issues associated with mould are urgent, and the risk of further damage to your home is of the utmost importance.

Once water gets into your home, the damage it causes can easily mean that you’ll need to replace insulation, drywall, and, depending on the extent of the damage, the framing.

Mould is difficult to remediate and costly in both the health issues it can cause and the dollar amount you will spend to mitigate the source.

If you notice any of the following eight signs in your home, contact a waterproofing professional immediately:

  • Water puddles in the basement
  • Water stains on the floor or walls
  • Leaks coming from the floor or walls
  • Condensation on basement windows or doors
  • Swelling or warped doors
  • The smell of dampness that doesn’t seem to go away
  • Visual confirmation of mould or mildew
  • Cracking on the floor or walls

If a water leak has gone unnoticed for a long period or moisture issues have not been addressed appropriately, your home’s foundation can be compromised and must be repaired.

Foundation repairs are handled by structural engineers and are more extensive than the waterproofing itself. If you notice cracks, leaks, or bowing in your basement walls, it’s most certainly time to call in a foundation repair specialist.

You chose a contractor, and they have amazing qualifications. Their reviews are fantastic, the company’s longevity in the market is impressive, and they have a solution for your specific issue. Great! You’re almost there!

Knowing and understanding the available options for getting rid of the water in your basement is essential to educate yourself on not just the solutions but also the causes. You can make sure it never happens again, and you will notice the warning signs if they ever show up again.

The different causes of water intrusion have different solutions, of course. One size does not fit all.

Depending on what your contractor has found, the possible solutions are as follows (and remember, it may be a combination of solutions):

Understanding Waterproofing Solutions

As important as it is to understand the causes of the water intrusion, it is equally important to understand what will happen in the course of resolution. Even interior remediation will most likely include at least some degree of demolition.

Here’s what to expect with an interior waterproofing system:

  • The team will dig a trench around the interior of your basement walls.
  • They will then lay down the drain system in that trench and, in most cases, install a sump pump.
  • Next, the crew will repour concrete as needed, applying chemical sealants if the situation calls for them.

Exterior waterproofing is extensive. Here’s what to expect:

  • All soil will be dug away from your foundation, usually to a depth of 7 or 8 feet.
  • The crew will dig a trench around the foundation and fill it with drain material and gravel.
  • Depending on your home’s specific issue, the crew may also apply chemical sealants and sheets of waterproofing material to the exterior foundation walls.

Both types of waterproofing work may also include yard redirecting water away from your home and gutter work with the same purpose.


The waterproofing solution that is right for you depends on your situation. Do your homework, learn your options, get quotes, take a lot of time before pulling the trigger on any basement waterproofing solution. If you decide you want to hire a contractor, take a look in our directory to find a basement waterproofing contractor near you.

Regardless of whether you need interior waterproofing, exterior waterproofing, foundation work, or a combination of the three, your home can be fixed. Sometimes the solution is as simple as diverting water away from your home.

In most cases, the best way to handle a water intrusion problem is to address the easy tasks first.

For example, have your gutters inspected, talk to a drainage expert about the grade of your yard, and then worry about the interior of the basement. If those solutions don’t fix the problem, you’ll likely need to move to the exterior.

Running a dehumidifier can help immensely with mould growth, and keeping windows or doors open can also help by bringing in fresh air and drying out the basement. You can do your part to keep issues from forming, but only with the issues you can see or smell. Looking for home builders? Look no further! MJS Construction Group has you covered.

More important is an inspection by a professional who can assess the status of your waterproofing methods, whether you are buying a brand-new home, constructing a home, or buying an older home.

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