How Interior Waterproofing Works: The Basics

Posted on: Sep 01, 2021


A sump pump used in most interior waterproofing methods

The average cost of a basement flood in Canada is around $43,000. This expensive repair is considered one of a homeowner’s worst nightmares. If you would like to avoid this scenario for an existing property, the first fork in the road is to choose between interior and exterior waterproofing.  

Interior waterproofing methods, also known as internal waterproofing methods, are designed to eliminate moisture from the inside of your basement. This means that no excavation work around the property is required to have this system set up. When compared to exterior waterproofing methods, interior waterproofing also gives you more cost savings. However, interior waterproofing also has its limitations. 

In this article, we explore how interior waterproofing works and make a comparison between exterior and interior waterproofing methods to help you better understand your options. 

A discharge pipe from a sump pump used in interior waterproofing methods

The Differences Between Exterior and Interior Waterproofing Methods 

As we mentioned earlier, making a choice between exterior and interior waterproofing is typically the first responsibility of property owners. Let’s quickly discuss their differences, which are summarized in the following table: 


  Interior waterproofing methods Exterior waterproofing methods
Location Inside the basement Outside the basement
Excavation required? No Yes
Sump pump required?  Almost always It depends 
Needs a waterproof membrane Yes Yes
Makes use of a weeping tile network Yes Yes
Water is kept completely out  No* Yes
The basement space is kept dry Yes Yes
Average cost Generally lower Generally higher

The table above shows us that both interior and exterior basement waterproofing make use of materials like waterproof membranes, weeping tiles, and a sump pump. However, even if the same group of materials is used, these are put together in completely different ways for interior and exterior waterproofing. 

For example, the weeping tile network for exterior waterproofing is on the exterior side. As for interior waterproofing, the weeping tile network is inside the basement. Furthermore, the waterproof membrane of interior waterproofing is on the inner wall while the membrane used for exterior waterproofing is on the outside, directly in contact with the surrounding soil.

*Exterior and interior waterproofing methods have different modes of keeping a basement dry. Exterior waterproofing is the only true waterproofing that keeps water out, which means that the water is kept away from the foundation wall and from the basement space itself. 

On the other hand, interior waterproofing is mainly about channeling water away with increased efficiency and less hassle. In this setup, water can still technically seep through the foundation wall but the water won’t really get to your basement space. We will explain how this works in the following section.

How Interior Waterproofing Works

Let’s go over the main components of interior waterproofing and its significance: 

The Trench and Weeping Tile Network 

After the leaky walls in your basement have been identified, a trench is made in front of these walls in order to install 4” weeping tiles. The weeping tile network is set up so that it leads to the sump pit or an existing storm sewer. This way, any leaks that go through the walls are caught by the weeping tiles and the water will be channelled accordingly. 

 The Sump Pump 

If a storm sewer is present, the weeping tile network can be directed to it. However, without a storm sewer for interior waterproofing, a sump pump (along with a backup sump pump) is installed in a strategically placed sump pit. Typically, this pit is placed in the lowest portion of the basement. 

The sump pump does more than redirect water that leaks through the problematic walls. The sump pit can also collect water that’s accumulated around the foundation and send it through the discharge pipe, away from your home. This helps to keep your foundation intact.     

 The Waterproof Membrane 

The waterproof membrane is the part that keeps your basement dry. It also helps prevent the leaks from contributing to the humidity of the space. It acts as an effective vapour barrier, spanning all the way from the ceiling to the top of the trench where the weeping tile is installed.

Rolls of waterproofing membrane used for interior waterproofing

Why DIY Waterproofing Methods Are Not As Effective 

Interior waterproofing may seem similar to some DIY methods, such as coating the inner surface of the wall with waterproof spray or paint. However, this is not the same as the long-lasting waterproof membrane used for professional interior waterproofing. In fact, some DIY products will only work for a few months.

When done by a skilled professional, interior waterproofing can efficiently channel water out, thanks to its weeping tile network and sump pump system. Because of this system, the foundation itself is kept relatively dry because the sump pump manages high water tables or accumulated groundwater. Professional interior waterproofing is thus able to reduce the hydrostatic pressure on the concrete. This waterproofing method can also prevent clay-rich soil from expanding and pushing against the foundation wall.  

Professional Interior Waterproofing Methods You Can Count On 

PRO Waterproofers is one of the most trusted waterproofing companies in Ontario. Through our years of service, we have provided innovative, effective, and thorough waterproofing solutions for all kinds of properties. We can assess all the waterproofing needs that your property has and recommend the solution or set of solutions for you – whether that means using exterior or interior waterproofing methods. 

In this article, we’ve extensively discussed how interior waterproofing works. We have also given you a glimpse of its counterpart, exterior waterproofing

If you have further questions for us or you’d like to take advantage of our FREE in-home consultation, contact us today

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