Drainage Issues: How Retaining Walls Can Help

Retaining walls provide property owners with a variety of benefits from increasing drainage and preventing erosion to adding to a home’s curb appeal and improving the landscaping. If retaining walls aren’t designed properly to account for proper drainage, it is likely that they will fail, resulting in extensive damage to your property. Whether you’re planning on installing a retaining wall on your own or hiring a professional, it’s essential to understand the purpose, types, and crucial features of retaining walls.

What is a Retaining Wall?

A retaining wall is a structure that can be created by many different types of material to retain soil and water behind it. While retaining walls were initially designed to keep a property’s landscape soil from eroding, homeowners are commonly choosing to incorporate these structures to increase their property’s aesthetic value and create more usable space. Retaining walls can be built from a variety of materials; some are easy to use while others have a shorter life span.

  • Concrete Blocks
  • Poured Concrete
  • Treated Timbers
  • Rocks
  • Boulders

Types of Retaining Walls

The properties of homeowners vary, meaning the reasoning or purpose for a retaining wall can differ from location to location. From drainage and erosion to needing more usable space, there are four common types of retaining walls, each designed with different purposes.

  1. Gravity: Large rocks or other materials can be used to design a gravity wall. A gravity wall holds the earth behind in place with the weight of the structure’s material. It’s recommended to use a gravity wall for shorter slopes as they can fail quickly.
  2. Piling: Long poles made of metal or wood are placed deep in the soil and raised above ground to create a wall. Because of the leverage created due to the placement in the soil, a piling wall is durable and can withstand high forces.
  3. Cantilever: Like the structure of piling walls, long poles are also used to construct cantilever walls. Cantilever walls have added strength from a second lever arm that’s extended into the hill, which increases its durability and stability. 
  4. Anchored: The design of an anchored wall has proven to be the most reliable type of retaining wall. Cables are driven into soil or rock behind the wall and fixed by an anchor wrapped around the wall. Anchored walls can be combined with other retaining wall designs to provide increased stability.

 

Why Proper Drainage is Important

Allowing for proper drainage in your retaining wall is extremely important as any built-up water puts additional pressure on the structure and can weaken the retaining wall’s ability to resist. If built-up water isn’t allowed to release, the weakest part of the retaining wall will give. This can be identified from a bulge, leaning outward, or buckling. Several methods can be incorporated when designing your retaining wall to prevent water from building up:

  • Weep Holes: When planning your retaining wall, small holes can be drilled through the wall, which will allow water to escape from behind the wall. Most commonly, the holes should be spaced evenly in a horizontal direction. If your retaining wall is higher than two to three feet, it’s encouraged to drill evenly spaced holes in a vertical direction to create a grid.
  • Drainage Pipes: Depending on the design on your retaining wall, drainage pipes may be a better solution. Perforated pipes can be installed behind the retaining wall allowing water to drain through the length of the wall. Depending on property type, the piping can be placed right above the footing or higher if necessary due to elevation. Taller walls may require more than one pipe.
  • Granular Soil: A soil mixture that is cohesionless and granular can be used as a backfill to allow water to access weep holes or drainage pipes easily. Materials of this consistency allow for water to travel more efficiently, thus preventing any being trapped. 
  • Grading: Executing proper grading on the soil behind the retaining wall also influences water buildup. Usually, the soil behind a retaining wall slopes toward the wall causing water to flow directly toward the retaining wall. Proper grading can be incorporated into the construction process to reduce the amount of water that approaches the wall.

Each of these methods will help reduce the amount of water building up behind your retaining wall, thus lessening the chances of bulging, outward leaning, and buckling. In many cases, homeowners are most successful when combining more than one of these methods, and, as a result, water pressure on your retaining wall will be drastically reduced.

How to Set Up Your Retaining Wall

Whether you’re choosing to hire a professional to build a retaining wall or choosing to do it yourself, it’s encouraged to have a basic understanding of the proper structure. If a retaining wall is built incorrectly, it could lead to significant issues for your property and landscaping.

  1. Base: Retaining walls must be built on a reliable base as it directly impacts the overall performance of the wall. The base should be set below ground level with the height of the wall in mind; the higher the wall, the further below ground the base should be. The base for your retaining wall should be made of compacted soil and around six inches of compacted sand and gravel.
  2. Backfill: Properly compacted backfill is a detail that is essential in the construction of a retaining wall and refers to the soil behind in the wall. Utilizing a cohesionless, granular soil such as gravel will help provide proper drainage. It’s recommended to start with about a foot of the chosen backfill material placed directly behind the wall.
  3. Drainage: When designing a retaining wall, developing a plan to allow for efficient drainage is vital. Without a proper drainage system, your retaining wall can weaken and give leading to damage to your landscaping. Along with backfill, a drainage system such as weep holes or drainage pipes should be installed.
  4. Height: Retaining walls can vary in height, meaning the height determines the weight it can withstand as well as how much reinforcement may be required. Different properties require different heights, but most commonly retaining walls are between three and four feet high.

Improve the Health of Your Property

Whether you’re having difficulties with proper drainage in your landscaping or looking to add to the aesthetic of your property, a retaining wall is an excellent addition. There are many different designs of retaining walls created with various materials, so learning what’s best for your property is essential. It’s vital to be sure that your retaining wall is designed and constructed correctly to alleviate any future issues. Contact a professional or begin building a retaining wall on your own to start improving the overall health of your property.