One of the best water management techniques is installing French drains. These robust improvements are made to function with water’s natural downward flow, reducing the numerous risks that come with not preventing water damage. A French drain is also called a curtain drain, foundation drain, footing drain, perimeter drain, or weeping drain.
A French drain allows for a strong foundation and basement and is durable, aesthetic, easy to install, and gives you control over where the water goes. However, it puts power, sewer, gas, and water lines in the ground at risk, requires a permit to construct, and cannot benefit certain areas.
French drains are a first line of defense for a building’s foundation, basement, and even the health and well-being of its occupants. They can be as aesthetically pleasing as they are helpful. They reduce the need for a sump pump system for your basement.
What is a French drain?
A French drain is a trench dug in the ground and filled with rocks or gravel to direct water away from a given area. It can have a pipe in it (or not).
A French drain appears like a rock drainage ditch from the outside and, when installed correctly, is a lovely hardscaping element. A drain pipe angled to move water away from the house is embedded in that gravel when necessary. A French drain on your property can be located by looking for the exposed pipe end on the incline.
Water cannot collect in the ditch because every component of the French drain is made to allow water to travel through. Water flows through the perforations in the perforated pipe and the gravel or stone.
The pipe is covered with landscaping fabric, preventing weeds, mud, and other debris from clogging the openings while allowing water to flow through. The pipe transports the water to a yard drainage area or the public sewer system.
Types of French drains
There are exterior and interior French drains with the exterior ones being the most common and the subject of this guide. On the other hand, interior French drains are dug into basements where the empty water into a small well to be emptied by a sump pump system.
The most common types of exterior French drains include the following:
1. Curtain drain
This shape is made up of a gravel-encircled perforated pipe. It is similar to a standard French drain in that the gravel or aggregate material extends to the ground’s surface and is left exposed to allow for water collection.
Still, a curtain drain is covered by soil where turf grass or other plants may be planted to hide the drain.
2. Filter drain
This design drains underground water. Filter drains are gravel-filled trenches that collect and move water with free-draining gravel and often have a perforated pipe in the bottom to collect the water.
They are widely used to drain roads and are often seen along the edge of main roads.
3. Collector drain
This design combines groundwater drainage with surface water or runoff water interception and connects to underground pipes to quickly divert surface water.
It preferably features a cleanable filter to prevent surface dirt from moving to the undercover area and clogging the pipes.
4. Fin drain
This shape consists of an underground perforated pipe with a thin vertical portion of aggregate material called the “fin” that runs perpendicularly upward along the length of the pipe for drainage to the pipe. The fin is 200 mm (7.9 in) long.
Construction costs for this type are lower than for a conventional French drain.
Advantages of a French drain
The main benefits of a French drain are as follows:
1. Allows for the construction of a strong foundation
Water can cause many problems inside and around a building’s foundation. A lot of water can weaken the soil around it, shift it, or soak right through foundation fractures to endanger its stability.
To avoid this, French drains assist in rerouting water away from foundations.
This would also cause massive damage to a basement’s area since water seeping through the basement walls can cause massive damage to the whole house. With a French drain, your basement is safe.
2. They’re durable
Due to their underground operation, these systems must be more resilient than most alternative drainage methods.
French drains are subject to hydrostatic pressure because of their subsurface construction, which causes water to exert this pressure due to gravity. Therefore, a trough will function more consistently the more durable it is.
3. It’s useful and aesthetic
French drains complete the task without making your house unsightly. There may be some reservations about digging a ditch, but once the drain is finished, it may be an attractive surface feature that does all its dirty job below the surface.
Gravel is available in various forms, dimensions, and hues that can harmoniously complement the surroundings.
4. Easy to install
One of the most accessible and affordable drainage solutions is a French drain. This is especially true if installing them won’t necessitate uprooting any external structures that are already in place.
5. You control where the water goes
These layouts allow residential and commercial clients to choose where redirected water is used. Builders can install pipes to direct water, for instance, into a drainage ditch, a street, or a low-lying portion of the land.
Disadvantages of a French drain
Here are some things to watch out for:
- When excavating underground, there is a chance that you could hit utility cables and conduits, which could electrocute you, compromise a gas main, or cause the lose of power.
- Without routine maintenance, French drains get clogged, adding to the problems associated with water management.
- You might need permits to construct them. Any contractor or property owner who proceeds with a project without one puts people, property, and the project in danger physically and financially.
- In drains that use gravity, sloping must be at least 1%; otherwise, water won’t move. This can be hard to achieve for some terrains.
- It will be more difficult for properties at the bottom of a hill to benefit from a French drain. In these circumstances, installing a sump pump might be necessary.
- Water rerouting is a delicate subject. To ensure your drainage doesn’t have a detrimental influence on the neighborhood, local authorities and other property owners must be considered and consulted.
Even with these downsides, French drains are still some of the best when it comes to keeping the foundation and basement of a house dry. Even then, you’ll still need a dehumidifier in the basement since moisture can damage the house from within.
How to build a French drain
French drain installations are not too complex. You will need three materials to install a French drain: aggregate, perforated plastic drainpipes, and water-permeable non-woven landscaping fabric.
The steps to construct a French drain are as follows:
1. Dig a trench at a gradient for the pipe
Select a site for the trench that slopes downward naturally, or dig the channel with a 1% gradient to construct your slope.
This will give gravity a chance to help the water drain to your chosen area. Create a trench to fit the pipe, surround it with aggregate, and cover it with a membrane.
2. Cover the trench with water-permeable landscape cloth
Lay the cloth across the bottom of the trench and up the sides. Maintain an adequate amount of cloth on each side of the trench to cover the pipe, much like wrapping a gift.
3. Add aggregate to the trench’s bottom
Fill the trench bottom to about a third with a typical landscaping aggregate. Any debris entering the system will pass through gaps in the huge aggregate, keeping the water moving fast and with fewer blockages.
A 1 to 2-cm wide aggregate is ideal.
4. Lay the perforated pipe
Lay the drain pipe of your choice with the perforated holes facing downward. Any other configuration will prevent the water from exiting the pipe until it is complete.
The French drain can be extended beyond the capacity of one pipe by using sturdy and reliable pipe connectors and couplers.
5. Fill the trench with more aggregate
More aggregate of the same size should be shoveled or tipped on top of the pipe in the trench. This should continue until the top of the trench is roughly 10 cm (about 3.9 in) below the gravel.
6. Use the remaining cloth to envelop the French drain
The aggregate and pipe should be covered with the landscaping fabric that was supposed to protrude from the trench’s edges. Make sure there is little to no space between the fabric’s edges.
This will stop debris from clogging the system by preventing it from entering the drain.
Finally, you can cover the French drain with soil or something similar without hiding its presence.
Are French drains worth it?
Property owners should always seek advice from a professional who understands drainage’s practicalities and aesthetics. The best method to take advantage of both is to add a French drain.
However, only if it suits your site and doesn’t create any other problems will it be worth your effort and money. Choosing a contractor you can trust can skip the risks and go straight to the benefits.
French drain installation has many advantages, but there are also certain negatives that a skilled drainage expert will ensure you don’t experience. Going it alone or accepting any contractor’s promises at face value could have the opposite result and cause many more issues.
Frequently Asked Questions
Will exterior French drain keep my basement dry?
An exterior French drain will keep your basement dry by reducing the amount of water that gets close to the basement.
Is it better to have a French drain in the basement or outside?
While both interior and exterior basements protect the basement from water damage and flooding, the interior one is better since it’s easier to install and service.
Will an exterior French drain prevent water in the basement?
A French drain does not prevent water from getting into a basement but channels it under and around the foundation before it can get into basement. Basically, a French drain diverts water from the foundation and the basement.