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Your home’s roof and exterior walls keep weather and water from entering your house from above. These systems shed water away from themselves to avoid water buildup and (ultimately) leaks.
But that water must go somewhere, and that somewhere is into the ground at your home’s foundation, where it can, and will, cause damage to the underground structure if steps aren’t taken to reduce the risk. Here’s everything you need to know about your home’s foundation drainage system and how it works to eliminate water damage from below.
What Is a Foundation Drainage System?
Foundation drainage systems are a structure or series of structures designed to remove excess and runoff water from the ground around your home’s foundation. System components move water away from the supporting structure of the house by collecting it and discharging it using gravity or pumps.
The system eliminates damaging water pressure and other problems affecting the footings, crawlspace or basement walls.
Why Is a Foundation Drainage System Important?
Every home must have some sort of water drainage system to prevent water pressure from building up against the foundation and causing damage or water leaks into the basement or crawlspace. Homes built on concrete slabs must also eliminate excess groundwater to avoid ground swelling and frost heave.
Types of Foundation Drainage
There are several ways to shed water away from your home’s foundation. Sometimes, a home’s foundation drainage may be little more than a sloping lawn. Other times it may consist of a complex system of underground pipes and pumps.
French Drain
A French drain foundation system consists of perforated underground pipes wrapped in landscape fabric and surrounded by gravel, buried in a trench encircling the house foundation’s exterior. French drains work to eliminate excess water that has seeped into the ground by collecting it within the pipes that transfer the water to a sewer or a distant location away from the home.
Foundation Surface Drain
Foundation drains consist of buried and wrapped perforated pipes surrounded by gravel that encircle the foundation’s exterior, similar to a French drain. However, the pipes are placed closer to the top of the foundation to act as a surface drain. Foundation drains collect water before it can seep into the ground and discard it downhill from the home.
Sloping Drain
A sloping drain is simply a landscaping design in which the ground surface near a home’s foundation forms an incline away from the house to direct water outward and prevent it from pooling or soaking into the soil. Sloping drains can consist of dirt or a hard surface such as concrete.
Sump Drain
A sump drain is a perforated pipe system that collects excess water and funnels it to a sump pit, where it’s then mechanically pumped out and safely away from the home’s foundation. The collection pipes may be located at the foundation’s interior, exterior or both, and the sump pit is located at the lowest spot inside the house.
Typical Components of Foundation Drainage Systems
Proper foundation drainage starts at the top and works its way down through a system of components.
Gutters and Downspouts
Your home’s gutters collect water flowing from the roof and divert it through downspouts to ground level, where the foundation drain system can take over.
Perforated and Solid Pipe
Perforated rigid or sometimes flexible pipes are buried underground near the foundation. Perforations throughout the pipe’s length allow water to enter the pipe and be diverted to pipes without perforations. Solid pipes transfer the water away from the home or into a sump pit.
Gravel and Fabric
Landscape fabric wraps around the perforated pipe sections to keep silt from entering and clogging the system. The wrapped pipes rest within a trench and are surrounded by gravel that promotes easy water flow within the ground.
Drainage Board
Some foundation drainage systems include a drainage board to promote water flow vertically to below ground level. Drainage boards are plastic sheets with protrusions covering the surface that allow water movement. The sheets are attached directly to the exterior of the foundation.
Trenches and Sump Basins
Except for simple sloping drainage systems, a trench encircles the foundation and contains the perforated pipe and gravel. Pipes in a sump system drain the water to a sump pit or basin. An automatic mechanical pump in the basin then discharges the water to the home’s exterior.
Design Considerations for Foundation Drainage Systems
The type and configuration of your home’s drainage system depend on several variables.
Moisture Level and Climate
Homes in areas with high precipitation levels and humid climates often need more robust foundation drainage systems than those in arid locations to deal with the larger water quantity.
Soil Type
The type of soil surrounding your home determines its ability to either shed or soak up water. Soils that are sandy and drain water well can often get by with simpler foundation drainage systems or none at all. Heavy, compact soils typically require substantial drainage systems that may incorporate components from more than one drain type.
Landscaping
Your yard’s landscaping plays a role in determining what foundation drainage system will work best. Sloping lawns often have different system requirements on the uphill and downhill sides of the house. For maximum effectiveness, foundation drainage systems must be clear of tree roots and obstructions that can impede the water flow or damage the system.
Code Requirements
Your municipality likely has specific rules about foundation drainage placement, depth and where water can be discharged. Code requirements always consist of construction minimums, and their scope may not be sufficient for your home’s drainage needs.
Pros and Cons of Foundation Drainage
As with any construction dealing with water, foundation drains have both positive and negative attributes.
Foundation Drainage Pros
- A proactive system can eliminate water problems before they happen
- Prevents water from pooling and becoming stagnant insect nurseries
- Reduces soil erosion
- Reduces damp mildew smells from finished basements
- Minimizes structural damage to the home
Foundation Drainage Cons
- Best when installed during the original home construction
- Retrofit installations are expensive
- Requires skilled labor and special tools to install
- Creates required maintenance tasks
- Systems can become clogged and require repair
Bottom Line
A foundation drain consists of various components, all designed to remove standing water from around the home’s perimeter and transfer it to a safe distance away. Houses built without the addition of a foundation drainage system run the risk of experiencing damage caused by water allowed to pool or soak into the ground around the home.
A general contractor, foundation specialist or even a landscaping company can assess your property to determine its needs regarding foundation drainage.
