Segmental Retaining Walls (SRWs): A Comprehensive Guide

Let’s Talk Segmental Retaining Walls

Retaining walls are essential structures used to hold back soil and prevent erosion, especially on steep slopes or areas where excavation has taken place. One type of retaining wall that has become increasingly popular over the years is the Segmental Retaining Wall (SRW). Segmental retaining walls (SRWs) are a popular choice for homeowners and landscapers alike when it comes to stabilizing sloped terrain or creating garden terraces. SRWs offer several benefits, including affordability, ease of installation, and versatility in design. An SRW is a gravity wall made up of concrete blocks or stones that are interlocked together and held in place by their weight and the friction between them. In this blog, we will discuss the proper construction of SRWs, the tools, equipment, or machines needed, and where a professional contractor or engineer may be required. We will also compare the use, suitability, performance, and cost of SRWs to other types of retaining walls.

Components of SRWs

The basic components of SRWs include blocks, geogrid, drainage, gravel footing, and backfill. The blocks are interlocking concrete units that vary in size and shape. The blocks' design (discussed in greater detail below) can range from basic rectangular units to more elaborate designs that mimic natural stone or brick. A gravel footing provides a stable base for the wall, while backfill material helps to provide additional support to the wall and helps with water drainage. Drainage is essential to prevent water buildup behind the wall, which can cause pressure that can lead to wall failure. Geogrid if required by the design is a reinforcement material that helps to stabilize the wall by interlocking with the blocks and extending into the backfill.

Different Types of SRW Blocks

Segmental retaining walls (SRWs) are made of different types of blocks, which can be installed either by hand or with machinery.

Blocks that can be installed by hand include modular blocks, interlocking blocks, and some types of hollow-core blocks. These blocks are designed to be lightweight and easy to handle, allowing homeowners and DIY enthusiasts to install them with minimal equipment and experience. They may also be necessary in sites with difficult access, where bringing in heavy machinery to move and install the blocks is difficult.

Blocks that require machinery for installation include large, heavy-duty blocks, such as precast concrete blocks or natural stone blocks. These blocks are often used for large-scale projects that require a higher level of stability and durability. Machinery such as excavators, backhoes, or cranes may be needed to lift and place these blocks into position.

Whether blocks are installed by hand or with machinery, it's essential to follow the manufacturer's instructions and use proper safety equipment during installation. When choosing the type of SRW block for a project, it's important to consider factors like the wall's intended use, the aesthetic appeal, and the durability of the materials. Homeowners and DIY enthusiasts should also consider consulting with a professional contractor or engineer before attempting to install SRWs, especially in larger-scale projects or areas with challenging soil conditions.

Tools, Equipment, and Machines Needed

DIY installation of SRWs requires basic tools, including a shovel, wheelbarrow, level, tape measure, string line, and rubber mallet. Specialized tools, such as a plate compactor, heavy equipment such as excavators, skid steers, and backhoes may be required for larger walls or more complex designs. Cutting tools such as saws or chisels may also be needed to cut blocks or stones to the desired size and shape. Renting tools may be an option if you do not have a tool and only need it for a short time, but often it is more cost effective to simply hire a contractor that is equipped with all of the tool required and has the experience skill to operate the tools efficiently and safely.

Construction of SRW

Planning:

Before you start, evaluate your site, taking into account the slope, soil type, drainage, and any other site-specific factors that may impact the wall's design or construction. Determine the wall's height, length, and layout, and calculate the number of blocks, geogrid (if required), and other materials you will need.

Site preparation:

Clear the site of any debris, vegetation, or obstructions that may interfere with the wall's construction. Level the site and mark the wall's location with stakes and string. If you a rotary laser is available, use it to determine existing and desired grades.

Excavation:

Excavate a trench for the wall's footing, which should be at least twice as wide as the block and deep enough to accommodate the block, gravel footing, and geogrid. Compact the soil at the bottom of the trench to provide a stable base.

Footing and drainage:

Install a layer of gravel in the trench to create a stable base for the wall. Install perforated drain pipes at the base of the wall and cover them with gravel. This will allow water to drain away from the wall, preventing damage and ensuring stability.

Block installation:

Begin installing the first course of blocks, ensuring that they are level and in line with the wall's layout. Use a level and rubber mallet to adjust the blocks as needed. Install geogrid reinforcement at the back of the first course, extending it back into the excavated area.

Additional courses:

Continue installing additional courses of blocks, interlocking them with each other and staggering the joints for added stability. Install additional layers of geogrid every few courses, extending them back into the excavated area and anchoring them to the soil.

Backfill:

As you install each course, backfill the space behind the wall with gravel and compact it with a plate compactor or hand tamper. Ensure that the backfill is level and provides even pressure on the wall.

Capstones:

Install capstones at the top of the wall, using adhesive to secure them in place. This will create a finished look and prevent water from penetrating the wall's top. To reduce costs or to vegetate the top of an SRW, capstones can be omitted.

Finishing touches:

After completing the wall, clean up the site, removing any debris or excess materials. Add landscaping elements, such as soil, plants, or mulch, to create an attractive and functional outdoor living space.

Note: These are general guidelines and may vary depending on the specific SRW block type and design. It's important to follow the manufacturer's instructions and consult a professional if you have any doubts or concerns about the wall's safety and stability.

Comparison of SRWs to Other Types of Retaining Walls

SRWs have several advantages over other types of retaining walls. Firstly, they are easy to install, and can often be completed by DIY enthusiasts. Secondly, they are highly customizable and can be designed to complement the aesthetics of the surrounding landscape. Thirdly, they are generally cost-effective and require minimal maintenance.

When it comes to retaining walls, there are several different materials and designs to choose from. Each option has its own advantages and disadvantages in terms of aesthetics, performance, and cost. Here is a more detailed comparison of segmental retaining walls (SRWs) to other popular types of retaining walls:

Masonry Walls:

Masonry walls are made of brick, stone, or concrete blocks. These walls have a classic, timeless look that is suitable for many landscapes. They are also durable and can last for decades. However, they are generally more expensive than SRWs and require a skilled mason to construct.

Concrete Walls:

Concrete walls are made of poured concrete that is reinforced with steel. They are strong, durable, and long-lasting. They are also customizable and can be designed to fit the aesthetic of your landscape. However, concrete walls can be costly, especially for taller walls, and require significant excavation and preparation before installation.

Stone Walls:

Stone walls are made of natural stones that are carefully selected and placed by hand. These walls have a rustic, natural look that can enhance the beauty of your landscape. However, they can be expensive and require a skilled stone mason to construct. Additionally, they may require frequent maintenance and repair over time.

Brick Walls:

Brick walls are made of fired clay bricks that are stacked and mortared together. These walls have a classic look that is suitable for many landscapes. They are also strong and durable. However, they can be expensive and require a skilled mason to construct. Additionally, they may require frequent maintenance and repair over time.

Steel Walls:

Steel walls are made of steel panels that are driven into the ground and anchored with concrete. They are strong, durable, and long-lasting. However, they can be costly and are not as customizable as other types of retaining walls. Additionally, they can corrode over time, especially in coastal areas.

Timber Walls:

Timber walls are made of pressure-treated wood that is stacked and secured with steel rods. These walls have a natural look that can complement many landscapes. However, they can be prone to rot and insect infestations over time. Additionally, they may require frequent maintenance and repair.

Gabion Basket Walls:

Gabion basket walls are made of wire cages that are filled with rocks or other materials. They have an industrial, utilitarian look that is suitable for many landscapes. However, they can be unsightly and may require frequent maintenance and repair. Gabion walls are also relatively cost effective compared to other types of retaining walls.

Crib Walls:

Crib walls are made of interlocking timber or concrete blocks that are stacked to form a wall. They are strong and durable, and can be customized to fit the aesthetic of your landscape. However, they can be expensive and require a skilled contractor to construct.

Pile Walls:

Pile walls are constructed using piles driven deep into the ground. They are suitable for retaining large amounts of soil and can be used in areas with unstable soil. However, pile walls can be expensive and may require specialized equipment for installation.

Mechanically Stabilized Earth Walls:

Mechanically stabilized earth (MSE) walls are made of soil that is reinforced with geotextiles or other materials. They are strong, durable, and can be customized to fit the aesthetic of your landscape. However, they can be costly and require significant excavation and preparation before installation.

Vegetated Walls:

Vegetated walls are similar to MSE walls or erosion control for slopes, but include vegetation planted on the face of the wall or slope. They provide a natural, eco-friendly look that can enhance the beauty of your landscape. However, they can be expensive and require ongoing maintenance to ensure the vegetation remains healthy.

Overall, SRWs offer several advantages over other types of retaining walls in terms of cost, durability, ease of installation, and customization. However, each type of wall has its own unique advantages and disadvantages, and the best choice for your landscape will depend on your specific needs and budget. A professional contractor or engineer can help you select the appropriate materials and design to meet your specific requirements.

When a Professional Contractor or Engineer is Required

While SRWs are a popular choice for DIY projects, there are situations where the services of a professional contractor or engineer may be required.

For instance, if you are planning to build a large retaining wall or one that requires specific engineering or design, it's important to consult a professional engineer or contractor. They will evaluate the soil type, slope, drainage, and other site-specific factors to determine the appropriate wall design, material, and construction method. In most areas in the Lower Mainland of British Columbia, Canada, retaining walls over 1.2 meters (or about 4ft) high or those supporting surcharge loads such as driveways, roads, or parking lots require a building permit, which will require a professional engineer's seal and signature.

In addition, if your property is in an area with a high water table or poor soil conditions, it's important to consult a professional. They can recommend the appropriate drainage and soil stabilization measures, such as the installation of geogrid or soil nails, to prevent soil erosion and wall failure.

Furthermore, if you are unsure about the structural integrity of an existing retaining wall or are planning to modify an existing wall, it's important to consult a professional. They can evaluate the existing wall's condition and provide recommendations for repair, reinforcement, or replacement.

Overall, while DIY installation of segmental retaining walls is possible and can save money, it's important to consult a professional contractor or engineer in situations where safety, stability, and compliance with building codes are critical. Trifecta Landscapes provides professional retaining wall construction services arranging the design, engineering, and installation of the retaining wall, ensuring that your retaining wall meets all safety and regulatory requirements while providing the functionality and aesthetic appeal you desire.

Cost of SRWs

The cost of building a segmental retaining wall (SRW) can be influenced by several factors, including the size of the wall, the type of materials used, the complexity of the installation process, and the amount of excavation needed. Excavation can be a significant factor in the overall cost of an SRW installation, as it can require additional labor and equipment to prepare the site for the wall.

The cost per square foot for an SRW can range on average from $40 to $80, depending on the specific project requirements. The type of materials used is one of the primary factors affecting the cost, with options ranging from basic hollow concrete blocks (that are typically installed by hand) to larger blocks (that require heavy equipment to move). Additionally, some SRW designs may require additional materials, such as geogrid, concrete footing, and drainage systems, which can add to the overall cost of the project.

The complexity of the installation process is another factor that can affect the cost of an SRW installation. While some homeowners may be able to install an SRW themselves with the right tools and equipment, more complex installations may require the services of a professional contractor or engineer, which can add to the overall cost of the project. Also additional excavation may be necessary to create a suitable foundation for the wall or to level sloped areas. Excavation can also be necessary to install drainage systems or to prepare the site for additional landscaping or hardscaping features.

Overall, homeowners should consider the long-term costs of an SRW installation when planning their budget. While SRWs are generally cost-effective compared to other types of retaining walls, they may require maintenance over time. Additionally, the quality of the materials used, the installation process, and the amount of excavation required can all impact the durability and lifespan of the wall, which may affect its overall cost-effectiveness.

Increasing Property Value with Retaining Walls

Retaining walls, regardless of type, can increase the value of a property in several ways. Firstly, they provide functional benefits such as increased usable outdoor space, which can be utilized for entertaining, gardening, or other activities. By creating level areas in otherwise sloping or uneven terrain, retaining walls can increase the amount of usable space on a property, making it more appealing to potential buyers.

Secondly, retaining walls can enhance the aesthetic appeal of a property by providing a visually appealing backdrop for landscaping features such as gardens, trees, or water features. Retaining walls can be designed to complement the style and architecture of a property, adding an attractive focal point and creating a more cohesive outdoor living space.

Thirdly, retaining walls can improve the overall functionality and safety of a property by reducing erosion and controlling water runoff. By redirecting water away from a property's foundation, retaining walls can help prevent water damage and improve the longevity of a property's structure.

Finally, retaining walls can provide a sense of privacy and security to a property, especially in urban areas where space is limited. By creating a barrier between a property and the surrounding area, retaining walls can increase privacy and security, making a property more attractive to potential buyers.

Overall, retaining walls can increase the value of a property by providing functional benefits, enhancing aesthetic appeal, improving functionality and safety, and providing a sense of privacy and security. If you are considering adding a retaining wall to your property, contact Trifecta Landscapes to learn more about our professional retaining wall construction services.

Our Services

Trifecta Landscapes offers professional retaining wall construction services, including SRWs, masonry, concrete, stone, brick, steel, timber, gabion basket, crib, pile mechanically stabilized earth, and vegetated walls. Our experienced team can help you choose the right wall type for your property and design a wall that meets your needs and preferences. We provide quality workmanship, attention to detail, and timely completion of projects, ensuring that you get the best value for your investment.

What to Take Home

In conclusion, segmental retaining walls (SRWs) are a cost-effective and versatile solution for slope stabilization and garden terracing. They consist of blocks, geogrid, drainage, gravel footing, and backfill, and various types of SRW blocks are available. While DIY installation is possible with basic tools, professional services may be required for larger or more complex projects that require specific designs or engineering. SRWs offer several advantages, including affordability, ease of installation, and increased property value by providing usable outdoor space and enhancing aesthetic appeal. Trifecta Landscapes offers professional retaining wall construction services, including SRWs and other types of walls, ensuring that clients receive the best value for their investment. To discuss your project and receive an estimate, contact Trifecta Landscapes today.