What Exactly is a deadman retaining wall anchor, deadman wall bracing, or more generally, what is a deadman in construction in more general terms? What are the purpose and design of these anchors? These are the questions, let’s get to the answers. Deadman wall bracing is a buried structure used to stabilize a retaining wall.
The deadman anchor consists of a large, heavy object that is buried in the ground next to the retaining wall. The weight of the backfill dirt covering the object anchors the retaining wall in place and prevents it from sliding downhill or leaning outward from the top.
A retaining wall can be designed to hold back earth, water, or other materials. When you build one it will need anchors that provide additional stability for the structure. These anchors come in many different shapes and sizes but they all have one thing in common: they provide a way to tie down the retaining wall.
If you’re interested in learning more about building a railway tie retaining wall and covering it, or perhaps you’re curious about how to install landscape timbers on a slope? If so, you’re in luck! We have two other articles that delve into these topics in detail. In “How To Build A Railway Tie Retaining Wall And Cover It,” with an overview on constructing a sturdy and aesthetically pleasing retaining wall using railway ties. And in “How To Install Landscape Timbers On A Slope,” we explore the best practices for creating a landscape structure on a slope.
What Can A Deadman Anchor Be Made Of?
When considering deadman anchors, you may be wondering about the materials that can be used. The options are surprisingly diverse, allowing for flexibility in construction. A deadman anchor can be fashioned from a variety of materials, ranging from a sizable rock or a carefully arranged pile of rocks to a sturdy piece of metal.
These anchors are buried strategically, ensuring that the top is flush with the soil surface, providing a solid foundation for the retaining wall to rest upon. By exploring different materials for your deadman anchor, you can choose the option that best suits your needs and complements the overall design of your project.
Deadman: Most Popular Kind Of Retaining Wall Anchor
The most popular type of anchor is called a deadman wall anchor and there are two different kinds that can be used for this purpose. First, you will need vertical poles that have been placed into holes drilled in the earth and then filled with concrete or steel rods if you are going through bedrock. Then you will need horizontal poles that have a loop at the end to attach cables or chains and then both ends of these loops will be hooked onto something heavy like boulders, car tires or steel plates. Check out the following video.
💡 When setting posts for a retaining wall, it is important to have at least two inches of concrete on all sides of the post. Having more concrete is better for structural integrity.
💡 Most rot in retaining walls occurs at the line where the concrete base meets the soil. To minimize rot, it is recommended to build up the concrete base and create round bases to prevent water accumulation.
💡 The dead man design consists of a triangle shape. It helps transfer the load of the soil on top of the footing to prevent the wall from lifting and leaning.
💡 Exposed wood in pressure-treated wood is vulnerable to rot. Treating the raw edges and exposed parts with pressure treatment or paint is important for longevity.
💡 The video mentions the use of pressure-treated wood from a local company that sells FSC-certified lumber, indicating sustainable harvesting practices. Sustainability considerations include the longevity of the structure and the toxicity of the treatment used.
💡 In the East Coast, there is a type of pressure-treated wood called “timber cell” that is treated with silicon instead of chemicals. It is said to last up to a hundred years and can be turned into compost when replaced.
The second type is called an anchor bolt which can also be used for vertical walls that either go straight up from the ground or are angled outwards. These anchors will be screwed into the earth, ideally with a set of bolts on each side to hold them in place better and then they can either have their own loop for attaching cables or chains (or sometimes just one) if it’s going through bedrock.
The first type is more popular because you don’t have to worry about driving the anchor rods all the way into bedrock, but they are more expensive and harder to install.
This type of wall is not only great for stabilizing a hillside or preventing erosion on an embankment, but it also provides opportunities for beautiful landscaping with shrubs, flowers, vines and trees.
Tips On Making A Deadman Anchor
Deadman anchors are essential for reinforcing the stability of retaining walls, and creating one is easier than you might think. One popular method involves using two pieces of durable landscaping timber, forming a cross shape. Begin by securely nailing the first piece to the retaining wall timbers, ensuring it extends deep into the ground for maximum support.
Next, affix the second piece to the first one with sturdy nails, making sure it extends downwards by at least the same length as the first piece. To provide adequate leverage, the second piece should extend at least 1 foot beyond the top of the retaining wall. By following these straightforward steps, you can create a robust deadman anchor, reinforcing the strength and durability of your retaining wall.
💡 Carriage bolts should be avoided when constructing the retaining wall as they can be difficult to remove and replace. Hex head bolts with washers should be used instead.
💡 Galvanized wood or galvanized hardware should always be used to ensure longevity and durability of the retaining wall.
💡 Pressure-treated wood is the most suitable option for ground contact, although redwood can also be used but won’t last as long.
💡 The base where the horizontal and vertical four by fours meet is not load-bearing, and all the load is transferred through the diagonal.
💡 The ends of pressure-treated wood should be protected from the elements using copper treatment, paint, or tar to prevent wood decay.
💡 A 2 by 12 is placed on top of the base four by four to prevent the retaining wall from moving when soil is added on top.
💡 The first run of the retaining wall is placed in the ground, and concrete is built up around it to shed water off the post.
💡 Bolts are crucial for holding the retaining wall in place. There are bolts on the top and bottom of the Deadman, as well as diagonal bolts.
💡 The combination of bolts on the diagonals, horizontal rails, and the plank supporting the bottom four by four provides the core strength of the retaining wall.
💡 The retaining wall should be constructed properly to ensure longevity of 30-50 years.
What is a Deadman Brace Retaining Wall Or A Deadman Anchor Retaining Wall?
- A type of retaining wall used to hold back soil on a slope or hillside[1][2]
- Uses “deadmen” as anchors tied into the retaining wall to provide stability[1][2]
How a Deadman Brace Works
- Deadmen are heavy wooden beams or timbers buried perpendicular to the wall[2][3][4]
- They act as anchors, resisting the pressure of the soil pushing on the wall[2][4]
- Cables or rods connect the deadmen to the retaining wall[2][4]
- Having deadmen installed every 6-8 feet helps brace the entire wall[5][6]
Building a Deadman Retaining Wall
- Dig trenches for deadmen and retaining wall footing[3][6]
- Install perforated drainage pipes behind wall[6]
- Position deadmen in trenches and backfill with compacted soil[3][4]
- Attach wall boards to deadmen with cable/rods[4][6]
- Backfill behind wall and compact soil in layers[3][6]
- Add additional courses of wall boards as needed[6]
So in summary, deadman brace retaining walls use perpendicular deadmen anchors to provide added strength and stabilization to the wall. The deadmen brace against soil pressure.
Citations:
[1] https://orlandi.com.au/what-is-a-retaining-wall-deadman/
[2] https://diyretainingwall.com/how-to-build-a-timber-wall-with-deadman-anchors/
[3] https://youtube.com/watch?v=7Db9_wT9kiU
[4] https://www.motherearthnews.com/diy/build-a-retaining-wall-zmaz86jfzglo/
[5] https://www.diychatroom.com/threads/deadman-yes-no.332849/
[6] https://www.thisoldhouse.com/landscaping/21018759/how-to-build-a-timber-retaining-wall
FAQ
Q: What is a deadman retaining wall anchor and how does it work with timber retaining walls?
A: A deadman retaining wall anchor is a buried structural element that helps stabilize and enhance the performance of retaining walls. For timber retaining walls specifically, the deadman system connects the wall to a buried anchor (usually a concrete block or pressure-treated timber) via tiebacks or tie rods. This system counteracts the soil pressure that would otherwise cause the wall to shift or fail, particularly in high wall applications. The buried deadman and the connecting tieback system work together to significantly improve the stability of the wall.
Q: How far should I bury a deadman anchor for a wooden retaining wall?
A: For wooden retaining walls, deadman anchors should be buried at a distance from the wall equal to at least 1.5 to 2 times the height of the wall. This ensures the anchor is placed in undisturbed soil outside the failure zone. The depth should typically be at least equal to half the wall height, with the anchor being placed at the same elevation as the tieback connection on the wall. For example, a 6’x6′ pressure-treated timber deadman for a 4-foot wall should be buried about 6-8 feet back from the wall at approximately 2 feet deep.
Q: Can I use deadman anchors for block retaining walls or just timber walls?
A: Deadman anchors can certainly be used for both block retaining walls and timber walls. For block walls (including segmental block walls and poured concrete block walls), the tiebacks often consist of rebar or specialized connectors that integrate with the wall structure. While installation techniques differ slightly between wall types, the core principle remains the same: the deadman provides resistance against soil pressure by transferring forces from the wall to stable soil behind the potential failure plane. Deadman systems are particularly important for high walls where stability concerns are greater.
Q: What materials can I use for a DIY deadman anchor on a small retaining wall?
A: For DIY deadman anchors on small retaining walls, you have several options. Pressure-treated timber (such as 6″x6″ posts) makes an excellent deadman for wooden retaining walls due to its preservative properties and resistance to decay. Concrete blocks or poured concrete deadmen provide excellent durability for any wall type. Railroad ties can also work if they’re preservative-treated. For the tieback connections, galvanized steel cables, rods, or heavy-duty chains can be used, along with appropriate hardware like eyebolts and turnbuckles. For very small retaining walls (under 3 feet), even landscaping spikes and treated lumber can create a functional deadman system.
Q: How do I identify when a deadman anchor has failed in my retaining wall?
A: Signs of a failed deadman in your retaining wall include visible bulging or bowing of the wall structure, the wall leaning forward significantly, horizontal cracks appearing along the wall face, or soil washing out from behind the wall. You might also notice the tieback system becoming visible or protruding as the wall shifts. Failed deadman anchors often result in terrace collapse or wall movement after heavy rain. If you notice any of these signs, especially in high walls or walls supporting structures, you should consult with a professional in foundation repair immediately, as wall failure could pose serious safety risks.
Q: How many deadman anchors does my retaining wall need for proper stability?
A: The number of deadman anchors a retaining wall must have depends on several factors: wall height, soil conditions, drainage, and surcharge loads behind the wall. As a general rule, deadman anchors should be placed every 6-8 feet horizontally along timber retaining walls and at vertical intervals of 2-3 feet on higher walls. For block retaining wall systems, follow manufacturer specifications. A professional engineer might recommend more frequent placement in challenging soil conditions or for walls supporting structures. For DIY projects on small retaining walls under 4 feet, deadman anchors every 6 feet horizontally usually provide adequate stability of the wall.
Q: Can deadman anchors be installed on existing retaining walls that are starting to shift?
A: Yes, deadman anchors can be retrofitted to existing retaining walls that are beginning to shift, though it’s more complicated than installing them during initial construction. The process involves excavating behind the wall to access the wall face, installing the tieback system through the wall, digging a trench for the deadman, installing the anchor, connecting the tieback, and then carefully backfilling. This retrofit can significantly enhance wall stability, but requires care not to further destabilize the structure during installation. For seriously compromised walls or basement walls, professional helical tieback systems might be more appropriate than traditional deadman anchors. The forum community dedicated to retaining wall construction has many examples of successful retrofits.
Q: How do deadman anchors differ from other tieback systems for retaining walls?
A: Deadman anchors differ from other tieback systems in several key ways. Unlike helical tiebacks, which screw into the soil, deadman anchors rely on passive resistance of a large buried mass. They’re typically more economical for DIY applications than mechanical earth anchors or helical systems. Unlike soil nailing, deadman anchors connect to a specific buried element rather than relying on friction along the entire length. Deadman systems are particularly well-suited for residential applications and can be installed without specialized equipment, making them ideal for timber retaining walls and structurally straightforward projects. They’re also commonly used in marine applications like seawalls where their mass provides excellent resistance against water pressure.
Conclusion
To conclude, understanding the importance of retaining wall deadman anchors is crucial for anyone considering building or stabilizing a retaining wall. These buried structures play a vital role in preventing the wall from sliding downhill or leaning outward, providing much-needed stability. If you’re interested in delving deeper into related topics, we encourage you to explore our articles on building a railway tie retaining wall and covering it, as well as installing landscape timbers on a slope. These comprehensive guides will provide you with step-by-step instructions and best practices for successful construction and landscaping projects. Remember to consider the materials and types of anchors you use, such as deadman wall anchors or anchor bolts, to ensure long-lasting stability. Whether you’re tackling a hillside stabilization project or creating an aesthetically pleasing landscape, incorporating these anchoring techniques is essential.
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