French Drain Waterproofing 101 for Realtors

Published On: December 12, 2022

When realtors think about basement waterproofing, most imagine creating a waterproof barrier using sealants and waterproofing paint. While this DIY project might help protect your client’s investment for a little while, it is not a long-term basement waterproofing solution because sealants do not address the root cause of the problem: excess water in the soil outside the home’s foundation walls.

French drain basement waterproofing prevents water from building up in the soil. If there is not excess water in the ground, there will not be water in the basement. However, French drain waterproofing is not to be confused with the trench drain, which is in fact ineffective when it comes to basement waterproofing. Other names for French drain basement waterproofing include drain tile, weeping tile, perimeter drain, footing drain, and foundation drain.

There are two types of French drain basement waterproofing: interior and exterior. We will discuss each type, as well as the cost of French drain basement waterproofing and things you as a realtor can communicate to your clients to help keep the soil dry around their foundations.

What is a French drain?

Generally speaking, French drains consist of a perforated pipe that collects water from surrounding soil and sends it away from a property’s foundation. They are helpful in many water diversion scenarios, whether it’s for landscaping or waterproofing. For basement waterproofing, French drains must be installed below the basement floor and direct the water either away from the foundation or to a sump pit.

French drain basement waterproofing works because it relieves hydrostatic pressure

French drain basement waterproofing prevents hydrostatic pressure from building up by collecting and channeling excess moisture in the soil away from the foundation.

Because basements are below grade, or underground, they are susceptible to water intrusion. If a foundation lacks good drainage around it, hydrostatic pressure will build up in the soil and press against the foundation walls. The force of the hydrostatic pressure can cause foundation walls to bow inward and sometimes crack. Eventually, water will get into the basement via these cracks in the foundation if the walls receive no relief.

Most new construction in the US has French drain basement waterproofing already installed. However, French drain basement waterproofing can be added to existing homes as well.

Two types of French drain basement waterproofing: exterior and interior

Exterior French drain basement waterproofing is installed around the outside perimeter of the foundation at the footing level.

Installing exterior French drain basement waterproofing for an existing property is a major construction project because it requires excavation down to the footer. Here’s how the professionals at USS install French drains for basement waterproofing:

  • The contractor first excavates down to the footer.
  • A waterproofing product is then applied to the foundation wall, followed by a protection board.
  • A shallow trench is dug beside the footer along the perimeter of the foundation and filled with gravel.
  • A perforated, socked pipe is placed in the trench and then covered with more gravel as needed. Depth of gravel can vary.
  • Finally, the contractor replaces the excavated soil.

Excess water in the soil will now flow through the pipe and be diverted away from the foundation via gravity or a positive drain.

It is important to reiterate that even though a trench is dug, the French drain is not identical to a trench drain. A typical trench drain has a metal grate above the trench to collect surface level water. French drains collect moisture from the soil, not just surface water, and are covered with gravel prior to replacing the soil (for exterior systems) or concrete (for interior systems) above it. To further distinguish, you can see the top of a trench drain but you should not see a buried French drain.

Interior French drain basement waterproofing is installed under the basement floor. It prevents hydrostatic pressure from building up in the soil under the foundation by channeling excess water into a sump pit, where it is then ejected away from the foundation.

Installing interior French drain basement waterproofing will mean using a jackhammer to break up the basement floor. After that, the installation procedure is as follows:

  • A trench is dug around the inside perimeter of the basement and then lined with gravel.
  • The perforated, socked pipe is placed into the trench and covered with more gravel.
  • A sump pump system is installed and connected to a drain system.
  • Wall flashing is installed on the basement wall to exterior grade height at a minimum.
  • The section of concrete basement floor is replaced to create a sealed system.

How much does French drain basement waterproofing cost?

The cost for French drain basement waterproofing for a homeowner depends on various factors, including where the property is located, the size of the repair, and how easy or how difficult it is to access the area of repair. The investment of protecting any property with French drain waterproofing is worth it, especially when the repair comes with a warranty.

Is French drain basement waterproofing a DIY project?

We do not recommend French drain basement waterproofing as a DIY project for any homeowner. Installation is a major construction project requiring either excavation down to the basement footer (for an exterior French drain) or using a jackhammer to break up the basement floor (for an interior French drain). It is better to leave this job for the professionals. A foundation repair or professional waterproofing contractor can also provide a lifetime warranty for interior French drain basement systems.

Additional methods for keeping water out of a property’s basement

If you want a dry basement, you do not want excess groundwater near the property’s foundation. Here are a few suggestions for your clients in addition to French drain basement waterproofing:

  • Don’t plant vegetation that needs a lot of water near the foundation – The excess moisture in the ground will find a way into the basement.
  • Make sure the yard is graded correctly – The yard, or exterior areas of the building, should slope away from the property’s foundation. If it doesn’t, have it re-graded by a landscaper.
  • Clean the gutters regularly – Clogged gutters cause water to spill over the side of homes and into the soil next to the foundation.
  • Install downspout extensions, if necessary – Downspouts undesirably release water next to the foundation. Extensions will channel the water away from the foundation before releasing it.

While French drain basement waterproofing might cost a bit more than simply using a sealant on the basement walls, it is the most cost-effective solution. French drains do not merely hold back the water like trench drains attempt to do. French drains remove the excess water from the soil.

If the property you’ve listed needs French drain waterproofing and is in our service area in Middle Tennessee, Southern Kentucky, or Northern Alabama, contact us today for a free inspection and repair estimate. We’re here to help!

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