With Frogs Group’s presence, choosing retaining wall builders near you has become easier and more reliable. The retaining walls by this group offer a combination of efficient functionality and attractive design, ranging from protecting against soil erosion to enhancing the visual appeal of yards and gardens. By leveraging Frogs Group’s experience and expertise, you can create a safe, sturdy, and visually pleasing environment for your home and enjoy its long-term benefits.

What is a Retaining Wall?

A retaining wall is a structure designed and built to resist lateral pressure from soil. These walls are used when the difference in ground levels exceeds the soil’s angle of repose (natural slope angle). Retaining walls provide lateral support to soil so it can be held at different levels on either side. Essentially, a retaining wall is engineered to hold back sloped soil that is not naturally stable and tends to move (usually a steep vertical or nearly vertical slope). Retaining walls are used to stabilize soil between two different elevations, especially in areas with unfavorable slopes or where steep slopes are intentionally created for specific purposes such as agriculture on hillsides or road embankments.

Design Considerations for Retaining Walls

A retaining wall is a vertical or nearly vertical structure designed to hold back materials (such as soil) and prevent collapse, sliding, or erosion. It supports soil where the natural slope angle is too steep and would otherwise collapse naturally. The key feature of a retaining wall is its ability to resist pressure from the retained material (usually soil). The most important design consideration is identifying and counteracting the tendency of the retained material to move due to gravity. This creates lateral earth pressure behind the wall, which depends on the internal friction angle, cohesion of the retained material, and the direction and magnitude of the wall’s movement. In homogeneous soil, the lateral earth pressure is zero at the top of the wall and increases to a maximum at the deepest point. The earth pressure pushes the wall forward, and if not addressed, can cause it to overturn. Additionally, any groundwater behind the wall not removed by drainage exerts hydrostatic pressure on the wall. It is assumed that all pressure or force on uniform height spans is applied at one-third of the lowest depth. This is an appropriate method for designing prefabricated structures.

To resist this pressure, proper drainage behind the wall is essential. Drainage reduces or eliminates hydrostatic pressure, improving the stability of the material behind the wall. Typically, dry-stacked retaining walls also serve a drainage function. For example, international building codes require retaining walls to be stable against overturning, sliding, excessive foundation pressure, and water uplift. Walls must be designed against lateral sliding and overturning with a safety factor of 1.5.

Types of Retaining Walls

Retaining walls come in various types; below are some common types discussed:

Mass Retaining Walls

Mass walls resist pressure through their own weight (made of stone, concrete, or other heavy materials) and often have a stepped, sloped back to improve stability by leaning on the retained soil. Mass walls for short landscaping walls are often built from dry-stacked stone blocks or concrete masonry blocks. Dry-stacked mass walls are somewhat flexible and do not require a rigid foundation. Today, taller retaining walls often use composite mass structures like geosynthetics (e.g., geocells), prefabricated facing, gabions (wire mesh baskets filled with stone), or crib walls (box-like structures made from precast concrete or wood filled with granular materials).

Reinforced Retaining Walls

Reinforced masonry or concrete walls on wide footings are mass structures whose weight and embedded reinforcing bars provide stability against overturning. Main types include:

Cantilever Concrete Retaining Walls

These walls are connected to their footings and can hold back large amounts of soil, so proper engineering is critical. They are the most common retaining wall type. The cantilever wall rests on a concrete slab, which is also backfilled with soil. The weight of the backfill and surcharge load helps stabilize the wall against sliding and overturning.

Reinforced or Buttressed Retaining Walls

These are cantilever walls strengthened with buttresses integrated with the wall slab and footing. Buttresses act as stiffeners to reduce bending and shear stresses by connecting the wall slab and footing. They are used for vertical walls taller than 8 to 12 meters, spaced evenly or about half their height apart.

Cantilever Walls

Cantilever retaining walls are constructed with an internal base of reinforced steel and cast-in-place concrete or masonry mortar (usually inverted T-shaped). These walls transfer loads like a beam to a structural footing and convert horizontal pressures behind the wall into vertical pressure on the ground beneath. To improve resistance to heavy loads, cantilever walls are sometimes strengthened with buttresses—short side walls perpendicular to the main wall. These walls require strong concrete footings at seasonal frost depths. They use much less material compared to traditional mass walls.

Mechanically Stabilized Earth Walls

These are walls made by mechanically reinforcing soil with steel bars or geotextile layers arranged in defined granular layers. If economically or geotechnically favorable, reinforced soil walls can be alternatives to reinforced concrete or other solutions and be used as retaining walls.

Soil Nailing Walls

Soil nailing involves inserting reinforcing bars (soil nails) into the soil as excavation progresses, strengthening it against stress. The nails are usually parallel and slightly angled downward, resisting bending and shear forces. Friction between the soil and nails stabilizes the system.

Anchored Retaining Walls

Anchored retaining walls can be built in any style mentioned but are strengthened by cables or rods anchored into rock or soil behind them. These anchors, typically installed by mechanical means or pressure injection of concrete with chemical additives creating voids in the soil, provide extra strength. This technically advanced method is useful for heavy loads or where the wall must be thin or weak.

Sheet Pile Walls

Sheet piling is a technique used in excavation support where interlocking sheets hold back soil with minimal disturbance. Acting like a temporary wall in slopes or excavations, sheet piles resist stress while being lightweight. They are often used in structures and infrastructure above or below water, are easy to lengthen or connect, and have stable joints.

Pile Walls (Secant and Tangent Piles)

These walls are formed by intersecting single concrete piles. Secant piles overlap by about three inches, while tangent piles are built side by side without overlap. These pile walls provide flexibility and stiffness, though sealing can be an issue.

Berlin Walls (Military Piles)

Originating from Roman military engineering, Berlin walls are quick, inexpensive, and simple to build, primarily for deep excavations. They are mostly temporary and less rigid compared to other retaining walls.

Cast-in-Place Pile Walls

Cast-in-place pile retaining walls are made by assembling sequences of piles drilled into the soil. Depending on the project, these may include soil anchors, reinforced beams, soil improvement techniques, and shotcrete layers. Used where sheet piling is applicable but vibration or noise limits sheet pile use.

Mechanically Stabilized Soil Walls

These walls can tolerate some relative movement. Their face is covered with granular soil, retaining the soil behind. Since they do not require concrete formwork or curing, they are easy to build. Soil nailing is often used, where steel reinforcing bars are inserted into slightly sloped soil and grouted.

Box Walls

Walls constructed by connecting boxes made of wood, steel, or concrete are called box walls.

Green Retaining Walls

Used for stabilizing gentler slopes, these walls incorporate slow-degrading geocellular structures applied to the slope surface, planting individual cells.

Clamping Retaining Walls

Made from rectangular reinforced concrete columns with longitudinal axes aligned to retain soil.

When planning a retaining wall project, factors like durability, proper drainage, and material selection should never be overlooked. These elements are all core parts of a well-executed hardscape design that ensures long-lasting and functional outdoor spaces.

Conclusion

Using retaining walls helps prevent soil erosion, create usable garden beds on sloped land, and provide decorative or functional landscaping features. Retaining walls can be standalone structures or part of larger construction projects like buildings. If a wall is over 1 meter high adjacent to a road or path, or over 2 meters high elsewhere, a permit is required. Independent and freestanding retaining walls typically do not require building code approval, but all constructions must be properly supported structurally.