Different Types of Foundation Waterproofing Systems Explained

water drainage

Foundation waterproofing plays a critical role in keeping any type of basement dry under extreme conditions. Exterior trenching systems and interior waterproofing coatings are the most common types of waterproofing systems.

These systems are different from each other, so understanding both can help you make an informed decision. Selecting the right system depends on a number of factors such as soil conditions and foundation type.

Exterior Waterproofing Systems

A French drain foundation waterproofing system is one of the most effective methods for keeping your basement dry, especially in areas that receive a heavy amount of yearly rainfall. As rainwater seeps into the soil, it collects along the footing of the foundation wall. The hydrostatic pressure of this standing water finds the weak spots in your foundation wall.

A French drain, or trench drain as it sometimes called, uses piping to divert the water away from the foundation wall. The piping is usually made of PVC, 6-inches in diameter. It is perforated to collect excess rainwater. The entire system is installed in a bed of gravel to prevent clogs from developing.

Although this system is extremely effective at eliminating basement flooding, it is rather expensive to install. Installing one of these systems requires the use of excavating equipment and is very labor-intensive. Even though an experienced do-it-yourself homeowner could probably tackle this job, it would consume a lot of time. Most homeowners who select this type of system hire a professional contractor.

Interior Waterproofing Systems

These foundation waterproofing systems are very different than underground trench systems, but they can be just as effective at preventing water infiltration. A residential foundation wall is usually constructed from one of two materials: poured-in-place concrete or concrete masonry units (CMU).

Both materials are porous in nature and allow water vapor to travel through the soil and foundation wall. The result is the dampness associated with most basements. To combat dampness, interior waterproofing systems form a membrane that prevents the water vapor from entering.

The most common systems use polymer-based compounds that penetrate the block or concrete to form a barrier against water and water vapor. Depending on the manufacturer, these systems can reach deep into the block or concrete, up to 4-inches.

Interior foundation waterproofing can easily be installed with a heavy-nap roller, much in the same fashion as latex paint. When compared to exterior systems, these foundation waterproofing systems cost considerably less.


The ideal foundation waterproofing system for your basement is a combination of both systems. Exterior trenching systems divert rainwater away from your home before it becomes a flood in your basement. Interior waterproofing systems prevent water vapor from infiltrating the basement. By utilizing a combination of both systems, you can ensure you’ll enjoy the benefits of a dry basement for years to come.