A retaining wall’s purpose is to hold back soil or water from the area that it was constructed in. This is to avoid the soil or water from being transported to another location or causing unfortunate accidents to other people during earthquakes and other emergencies.
Aside from keeping soil back, retaining walls can also be used as a decorative piece in a property’s lawn. Because there are so many uses of retaining walls, they are often built to last. This would mean that when a retaining wall is constructed, the owners would want it to last for a long time. However, this is not often the case.
When you drive around a city or neighborhood, it is highly possible to see failing retaining walls almost everywhere. The main reason for the failure is usually a poor or nonexistent drainage system.
What does “drainage” mean?
When a retaining wall is built, it is usually constructed as a structure that will fully enclose a certain amount of soil. This keeps the soil from being eroded to other nearby areas. However, in the process of gating the soil, other materials and debris can also be kept inside the walls until it is manually removed or if it has another path it can go to. One of the materials that are held by the retaining wall is water.
Water usually comes from rains, and it is one of the materials that will stay inside the retaining wall, along with the soil. As long as it will be dried by the sun or the air, the water will stay around the retained area and will not go anywhere. With this comes a major problem, as water tends to be heavy. If the owner wants the water to not be stuck inside, they will have to drain the water, hence the need for a drainage system.
A retaining wall’s drainage system requires several components, some of these are a drainage stone, a landscape fabric, a drain pipe, and an outlet. When you have a functional drainage system for your retaining wall, this would mean that the water from rains and other sources will not be stuck inside your retained area as it will make its way to the drains.
Does every retaining wall need drainage?
There are many home and property owners who are wondering whether every retaining wall needs a drainage system. After all, having one installed will mean that the procedure will require more time, money, and effort. To answer this question, many professionals would say that yes, drainage is required in most retaining walls. Although it will be an extra expense, contractors would say that drainage is definitely worth the money, and no retaining wall should be made without drainage in mind.
As mentioned above, the main reason why many retaining walls fail is due to the lack of or an improperly installed drainage system. It is no secret how most construction materials need to be kept away from moisture, as the latter is the number one’s enemy. In this case, the water that is stuck inside the retained area can be heavier and heavier as time passes, as it does not have anywhere to go to. Depending on the make and material of your retaining wall, it will fail and crumble sooner or later, as the water will be too heavy for the wall to keep in.
If you want your retaining walls to keep doing their functions, such as:
Keeping soil in place
Most retaining walls are constructed to keep soil in place, as they are great in combating soil erosion. They are also helpful in segmenting parts of your property, which is much needed in uneven soil. Retaining walls can be used in residential properties but also for large scale purposes in the commercial and industrial industries.
Protecting you, your family, and your neighborhood
Because retaining walls keep soil from eroding, it can assist in keeping your neighborhood safe during unexpected incidents such as earthquakes and flooding, which can result in a landslide. If the soil around the sloped areas in your property is properly retained, you will not have to worry that the soil will fall in your home, causing unwanted accidents.
Acting as a border between two properties
Retaining walls are also very efficient in acting as a boundary between two properties, and are very effective in keeping out unwanted occupants around your property. There are many commercial buildings in the United States who have opted to have a retaining wall constructed around their stores, as they can also be used to hold back soil, keeping their establishment safe and secure.
Making your landscape look appealing
Aside from keeping soil in place, retaining walls are now being used as a structure that adds visual appeal to a certain property. In fact, having one can even increase your home or building’s appraisal value. Because of this, many experts in the real estate industry recommend having them constructed, as they are guaranteed to increase the value and are also high in ROI or Return of Investments. Retaining walls can also be used in creative landscaping and gardening.
A properly and carefully planned and executed drainage system is needed.
When do retaining walls need drainage?
As was mentioned before, many experts in construction would definitely recommend having a drainage system in place for most retaining walls. Doing this will help your retaining wall last for a much longer time. However, having one installed will still be optional for the owner, as they might not want to have one at the moment, or might think that drainage is overkill if they are only using their walls for a minor purpose such as gardening.
Despite this, there are specific instances when a retaining wall will definitely need a drainage system, no matter what.
Cases when a drainage system is absolutely required and necessary:
- Drainage is necessary when your retaining wall is 4 feet or taller.
When you are building or have already built a retaining wall that has reached a height of 4 feet or taller, deciding whether to install or not to install a drainage system is out of the question. This is because when a retaining wall is constructed with a taller height, it will be expected to carry a bigger and heavier amount of soil. If a tall wall like this fails when it is no longer able to support the weight from water backfill, the event can be extremely dangerous and damaging to nearby people and properties.
- Drainage is necessary when your retaining wall has poor soil.
One of the most important factors that need to be studied and taken into consideration is the condition of the soil in the area where the retaining wall will be built. If the soil in the area has a poor drainage capability, this would also mean that the possibility of the water to be stuck on its surface will be increased, as it does not seep into the soil. An example of a poor draining soil is clay. Once you have inspected your soil and saw that it is poorly draining, you will need to have a drainage system in place, even though your wall is below 4 feet.
- Drainage is necessary when your retaining wall is made of concrete or cinder blocks.
There are many materials that can be used in building a retaining wall. Depending on the function it will need to perform, retaining walls can be constructed using bricks, stone, or steel. If your wall is made of masonry units such as concrete and cinder, it would be best to have a drainage system in place. This is because these materials are impervious – which means that their property does not allow moisture to penetrate its surface, allowing water to be stuck and backlogged for a long time.
- Drainage is necessary when your retaining wall is placed in an uneven area.
Because retaining walls are often placed in sloping and uneven areas, they will need to be made in a way that will make them do their function more, and this will only be possible when they have a drainage system. The reason for this need is that uneven areas will often have water stored around the area and unless they have a path to go through, the water will stay inside the uneven soil. This will also be the case when a terraced or tiered wall is built.
- Drainage is necessary when your retaining wall is placed near a water source.
In some areas, there will be some buried water sources such as a hose line, water line, and fire hydrants that can cause problems with moisture around your walls. If your retaining wall will be placed near these sites, a drainage system will be absolutely necessary. This also applies when there are gutters and groundwater around the place, as it will also cause some issues that will probably affect the stability and rigidity of your retaining wall in the long run.
- Drainage is necessary when your retaining wall is constructed for a municipal or commercial project.
When a retaining wall will be constructed in a residential property, it is common for the owner to be the only one to decide on some important choices such as whether they will have a drainage system installed or not. However, if the retaining wall is constructed for larger scale projects such as a municipal or commercial one, having a drainage system will absolutely be required. This is because owners should not take any chances for these projects, as building a retaining wall that is bound to fail in a short time will be a danger to the public. If a retaining wall is constructed for these purposes, it should be guaranteed to be safe and secure for the people, and this will only be possible if the wall is done properly with a drainage system in place.
What are the main components of a drainage system?
Drainage systems allow water to be transported to other areas, making your retaining wall only carry and support the soil around the place where it was installed. There are three main components of a drainage system that allows it to do its job properly.
Drainage Stone or Aggregates
In order for a drainage system to be in place, the number one component is a stone or aggregate. Some examples of recommended materials are loose gravel, crushed stones, and crushed rocks, as they do not hold water. These materials will be backfilled behind the retaining wall, which would usually be placed around 6 to 8 inches deep.
Landscaping fabrics or filter fabrics are non-woven materials that will prevent other materials from clogging the drainage stone and makes sure that rocks and soil will not be mixed together. Landscaping fabrics also assist in keeping your retaining wall from being stained due to frequent exposure. Fabrics are often placed behind the retaining wall by digging a 6 to 8 inch trench and placing one end of the fabric on top of the wall while the other end will be placed at the lowest point of the trench.
A drainage pipe helps in providing a path to the water and collects the water to have it drained in a spot away from the retained area around the wall. There are many types of drain pipes that will be better for your specific need. One example of a drain pipe is called a perforated pipe which is often installed at the bottom of the retaining wall. It is also possible to cut holes in the pipe, also called “weeping holes,” for better drainage. A pipe outlet (the hole at end of the drain pipe that transports the water and lets it out of the retained area) is necessarily placed every 30 to 50 feet along the wall.