In this article, you will learn about the pros and cons of interior vs exterior French drains.
Basements are the most flood-prone areas of any home. After all, they are located below the ground’s surface. That’s why building codes in some states require the installation of exterior or interior French drains (aka drain tiles).
These systems are your best chance of averting flooding, water damage, and mold in the basement. Basement flooding cleanup can be very troublesome and expensive. But how can you know which type of system best meets your home’s needs? Here’s what you need to know.
Exterior French Drains
An exterior French drain is typically located along the exterior perimeter of a building’s foundation. Its purpose is to collect and divert water away from the foundation before it can infiltrate the basement or crawl space. Here’s how it is typically installed:
- Trench Excavation: A trench is dug next to the foundation walls of the building. The depth and width of the trench can vary depending on the specific needs of the drainage system and the local conditions, but it is generally several feet deep and wide.
- Perforated Pipe: A perforated pipe, typically made of PVC or another durable material, is placed in the trench. The pipe should have perforations or holes that allow water to enter and be carried away.
- Gravel or Drainage Material: The trench and perforated pipe are then covered with a layer of gravel or another suitable drainage material. This material helps filter the water and directs it towards the pipe.
- Filter Fabric: To prevent clogging of the drainage system, a filter fabric or geotextile material is often placed over the gravel or drainage material.
- Backfill: The trench is filled back in with soil, and the surface is typically sloped away from the building to encourage water to flow away from the foundation.
- Outlet: The end of the perforated pipe is directed towards a suitable outlet, such as a sump pump, a drainage pipe leading away from the property, or a dry well.
When water pools around the foundation walls, it enters the pipe and drains away to a sump pump inside the house – or by gravity, but your yard must have a steep incline for the system to drain water away easily.
Installing exterior drains is more troublesome because it involves removing and replacing landscaping, driveways, sidewalks, porches, decks, etc. Another drawback is that maintenance is difficult, involving expensive exterior excavation. The pipe is prone to clogging over time as it’s buried underneath several feet of soil.
It can also be less effective in cases where water infiltration occurs through cracks or gaps in the basement walls.
Interior French Drains
An interior French drain also consists of a perforated pipe, but it’s installed around the perimeter of the basement floor. Like exterior drains, the perforated pipe is surrounded by gravel to filter out dirt and sediments. The pipe collects water from the basement wall floor joint as it enters and carries it to a sump pit, where a pump removes it from the foundation.
Installing interior drains in existing homes is not as disruptive and labor-intensive as exterior drains. Preparation consists of removing belongings away from basement walls and using a jackhammer to remove concrete.
Moreover, maintenance of interior drains is easier because the pipe is more accessible. Also, the pipe is less prone to clogging because it’s not buried in several feet of dirt. Another plus is that interior systems are protected from the elements, soil conditions, or roots growing into the drainage system. Also, they can be installed year-round, no matter the season.
However, interior French drains do not prevent water from infiltrating the foundation; they only manage water that has already entered the interior space. They may also require maintenance of the sump pump and drainage system.
Interior vs Exterior French Drains: Conclusion
When it comes to interior vs exterior french drains, both provide effective protection against flooding and water damage in your basement. Yet, due to the costs and difficulty of installing and servicing an exterior drain on existing houses, it may be better to install interior drains. Just remember interior French drains only manage water that has already entered the interior space.
Note: if you’re building a new home, take into consideration your local building code. In any case, always consult a basement waterproofing specialist to determine the correct type of drainage system for your home.
If you need professional water damage repair and mold removal for a water-damaged basement, contact your local PuroClean office.
