Why St. Louis Residents Choose Concrete Retaining Walls

Growing Soil Erosion Issue in St. Louis

Average annual rainfall in St. Louis is approximately 44 inches per year. Heavy rainfall storms occur frequently and greatly strain our city’s drainage systems. In addition to heavy rainfall, many of St. Louis’ neighborhoods have hilly properties, such as Dogtown and Clayton-Tamm, whose terrain creates erosion paths due to elevation changes. When clay soils found in the majority of St. Louis are saturated, they become extremely heavy and apply intense downward force on any hillsides they sit on, thus greatly increasing the potential for the clay soil to move. Additionally, the frequency of flash flood events has been on the rise in the past several years, leaving drivers stranded and causing thousands of dollars indamages to multiple properties in the greater St. Louis metropolitan area.

Damage to Properties Caused by Soil Erosion

Property damage from soil erosion not only affects the aesthetic look of landscaping; it also threatens the structural integrity of a home or building. Water running off a property will carve out channels in a yard and wash away the soil that holds the foundation of a home or building together. Water will then run under the home or building into the basement area and create voids (spaces) under the home or building as it continues to erode the soil. As saturated soil presses against the foundation walls of a home or building, the pressure applied to the walls increases exponentially, resulting in water seeping into cracks and joints in the walls. As driveways and patios lose the soil underneath them, they begin to crack and settle and eventually fail. Areas of a property located down slope from areas experiencing severe erosion issues experience sediment accumulation that causes a build-up in storm drains and ultimately kills all vegetation in the affected area.

Why Concrete Retaining Walls Are Superior to Other Options

Strength and Durability

When properly designed, a concrete retaining wall can withstand extreme lateral forces from heavy, saturated soil that would quickly collapse other types of materials. A reinforced concrete structure will not rot, rust, or be damaged by insects that will compromise a timber retaining wall in less than five years. Interlocking block-type retaining walls will continue to shift or separate over time, whereas a poured concrete wall provides a permanent, monolithic barrier that will remain intact forever. The high compressive strength of concrete makes it the best choice for taller walls exceeding four feet high, where the structural demand is much higher.

Long-Term Cost-Effectiveness

While the initial cost of constructing a concrete retaining wall may be greater than that of other materials used for retaining walls, the long-term value of a concrete retaining wall far exceedsthat ofe other materials used for retaining walls. A concrete retaining wall will typically last 50 to 100 years with virtually no maintenance required, compared to 15 to 25 years for a treated timber retaining wall. Homeowners who invest in concrete retaining walls will save money repeatedly on replacement costs and the inconvenience associated with replacing retaining walls. Claims made by homeowner insurance companies to repair foundation damage caused by erosion are usually many times more expensive than the original investment in a concrete retaining wall system.

Design Considerations

Drainage Behind Walls

The most common reason why retaining walls fail is poor drainage behind the wall. Water that accumulates behind a wall causes the water to apply hydrostatic pressure to the wall. If this pressure becomes too great, even a well-built wall can be bowed or toppled. Therefore, proper drainage design behind the wall is essential. Weep holes are drilled at regular intervals along the length of the wall, allowing water to escape from behind the wall instead of accumulating behind the wall and applying excessive pressure to the wall. Perforated drain pipes are installed behind the wall to collect and redirect groundwater away from the wall. Gravel backfill is used to create a permeable zone that allows groundwater to drain toward the drain pipes.

Requirements for Foundations

To prevent settling and tipping over time, every concrete retaining wall needs a strong foundation. The foundation of the wall must extend beyond the frost line to prevent heaving. In the St. Louis area, the frost line extends about 30 inches deep. Typically, the footing of a wall is one-half the height of the wall plus one foot wide for stability. Compacted soil is necessary for uniform support of the footing, preventing uneven settling.

Factors That Influence the Placement of Walls

Placement of retaining walls is influenced by various factors, including water flow direction and soil composition. Walls placed at the bottom of slopes will catch runoff before it achieves enough energy to cause erosion downstream. Many times, multiple short walls are placed in a tiered fashion down a steep grade and perform better than a single long wall built at the bottom of the grade. Utility lines, property lines, and existing plant life all need to be considered when determining the optimal placement of a retaining wall.

Repairing Previous Damage

For some homeowners, retaining walls are constructed after significant amounts of damage have occurred from previous erosion activity. Repair of slope damage before the construction of a retaining wall is usually necessary, including bringing in engineered fill material and compacting the eroded area. Use of geotextiles may be necessary to stabilize severely damaged slopes before wall construction begins. Trees with exposed roots present special considerations since the tree root system helps stabilize the slope and reduces the possibility of future erosion. Assessment of the property and trees determines whether repairs need to take place before wall construction, or whether the wall can help to stabilize the property as-is.

Permits and Compliance Issues

The City of St. Louis Building Department generally requires a permit for the construction of almost all retaining walls, especially those that are over three feet in height. Permit applications filed through the One-Stop-Shop Program generally receive immediate approval for simple residential projects. Plans illustrating wall size, footing detail, and drainage plan must be included with the permit application. City inspectors will verify footing size and placement before concrete is placed and again at completion of the project. Walls built close to property lines may require additional approvals to ensure compliance with setback regulations.

Benefits of Using a Professional Contractor

Retaining walls constructed using concrete demand professional knowledge of soil mechanics, structural engineering, and drainage design. Contractors familiar with local soil conditions and water table depth in different neighborhoods of St. Louis can properly design retaining walls for specific property conditions. The use of specialized equipment, including concrete pumps and vibration tools, assures complete consolidation and maximum strength of the concrete wall. Professionals are insured against liability and workers’ compensation, protecting homeowners against possible construction-related injuries. Contractorswhot provide a warranty assure that the structural integrity of the wall will be maintained and provide homeowners with peace of mind.

Increasing Property Values

Well-planned and installed concrete retaining walls create new outdoor space on sloping property sites and enhance the curb appeal of a property. Outdoor spaces created by terracing a yard can serve as garden spaces, patio spaces, and recreational spaces that increase property value. Real Estate professionals state that erosion prevention systems positively impact buyer perception and marketability of properties. Buyers have a difficult time purchasing a property with obvious erosion problems, and properties with visible erosion problems tend to sell at discounted prices. Investing in a quality retaining wall system protects the property owner’s current investment and potentially increases the resale price of the property.

Incorporating Vegetation and Aesthetics

There are many ways modern concrete retaining walls can incorporate design elements and styles. Concrete retaining walls can be finished to resemble natural stone textures and create a rustic look and feel without compromising structural integrity. Patterns of brick or ashlar can be created using form liners in the concrete during the casting process. Some homeowners prefer to finish the surface of the retaining wall with a stucco or stone veneer finish to create a visually appealing appearance. Planting beds strategically located at the base of the retaining wall softens the appearance of the wall andaddsd color. Vines and plants growing on the retaining wall provide an organic covering to improve the overall appearance of the wall.

Protecting Your Investment

It is important to act early to minimize repair costs and preserve the integrity of a property that is experiencing erosion. At St. Louis Concrete Works, we specialize in designing and constructing concrete retaining wall systems that address the unique erosion issues of each property. We assess the slope conditions and analyze the drainage patterns of each property, and develop a solution to stop erosion and protect the foundations of the home or building. We take care of all permit applications and coordinate with city inspectors to ensure that all of the applicable city regulations and ordinances are followed. From assessing the condition of your property to completing the final project, we provide you with a durable erosion control solution that will protect your most valuable asset for generations to come.