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Allan Block System

Commercial Installation Manual for Allan Block Retaining Walls
Check out all of the information we have on how to build a retaining wall and attend an AB Contractor Certification Training to learn the proper techniques to ensure top quality retaining walls are built.
   

Allan Block Retaining Wall Products and Collections
A Complete Family of Wall Products
The Allan Block Collections give you a choice of styles to meet your site and design requirements.
   

AB Collection - Retaining Wall
The AB Collection is our most popular retaining wall collection.
Whether you are building a simple raised garden or tackling a major hillside, the AB Collection will provide just what you need.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Collection.
   

AB Aztec - Retaining Wall
AB Aztec Collection brings ancient sophistication to modern retaining walls.
Whether you are building a simple raised garden or tackling a major hillside, the AB Collection will provide just what you need.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Aztec Collection.
   

AB Metropolitan - Retaining Wall
With minimalistic aesthetics and smooth clean lines, the AB Metropolitan line of blocks main focus is on functionality
This style offers a solution for a variety of wall applications, ranging from small residential to large-scale commercial projects.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Metropolitan Collection.
   

AB Europa - Retaining Wall
The AB Europa Collection offers the look and feel of weathered stone to the landscape.
The hand laid stone effect brings European old world charm and distinction to any retaining wall project.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Europa Collection.
   

AB Fieldstone - Retaining Wall
AB Fieldstone is our �Green� retaining wall product. This two-piece system has a facing unit and an anchoring unit.
Allan Block has opened the door to many benefits that are not only Green, but Natural and Friendly as well.
Chart showing multiple sizes, and shapes.
Photos of projects using our AB Fieldstone Collection.
   

What is a Retaining Wall
Gravity Wall or Geogrid Reinforced Wall?
Types of Retaining Walls
Understanding the dynamics of How Retaining Walls Work   Allan Block Video Logo
   

The Allan Block System - Engineered for Simplicity
Built-In Interlock
Built-In Setback
Built-In Drainage
Hollow-Core System
   

Gravity Retaining Walls
A retaining wall that relies solely on its own weight to stand up is called a gravity wall.
Setback and Sliding Wedge
Leverage and Total Unit Mass
Gravity Wall Maximum Wall Heights
   

Sample Gravity Wall Calculations
Analyze a gravity wall with the following site conditions:
   

Reinforced Soil Walls
When retaining wall heights exceed those listed in the gravity wall chart, geogrid can be added to provide a stable retaining wall condition
Geogrids are flexible, synthetic meshes which are manufactured specifically for slope stabilization and earth retention.
Positive Interlock
External and Internal Stability
   

Other Reinforcement Options
Masonry Reinforcement
Earth Anchors
No-Fines Concrete
Soil Nailing
   
Plan/Design

Retaining Wall Planning
Develop an accurate understanding of the jobsite before beginning any design, engineering, or construction on a project.
Site Geometry including Soils.
Water Management including Grading, Drainage, Surcharges, Slopes, and Setback.
Global Stability
   

Retaining Wall Design
Proper retaining wall design requires evaluation of the following:
Wall Location, Wall Height, Structural Requirements, and Total Structure.
Materials and Site Checklist Prior to Construction
Check Materials, Delivery Storage, Wall Rock, Backfill Soils, Foundation Preparation, and Geogrid Layout.
   
Build with AB, AB Aztec, AB Metropolitan, and AB Europa Collections

Gravity Retaining Wall Construction
Site Prep and Excavation
Install Base Material and Base Course
Install Wall Rock
Install Additional Courses
   

Stepping up the Base Course on a Slope
   

Reinforced Wall Construction
Site Prep and Excavation
Install Base Material and Base Course
Install Wall Rock and Backfill Material
Compaction, Install Geogrid, and Install Additional Courses
Installation Steps to Build a Proper Base Trench for AB Retaining Walls   Allan Block Video Logo
   

Modifying Blocks and Caps
Inside and Outside Corners
Cutting Caps for Corners and Curves
Altering Blocks
Construction Tips for Patterned Walls
   

Working with Geogrid
Retaining wall block can be used to construct walls that retain, or prevent the movement of the soil. The maximum height these walls can be built without the use of reinforcement is dependent on these primary conditions.
How Does Geogrid Work?   Allan Block Video Logo
   

No-Fines Concrete Backfill
Use of AB No-Fines Concrete Backfill has increased our ability to install reinforced retaining walls in locations where typical construction would not be possible because of property line constraints or limited excavation options.
No-Fines Engineering Properties
   

No-Fines Concrete Backfill
No-Fines Concrete Installation Steps
Additional Courses
Finishing Options
No-Fines Chart
   

Working with Soil
The soils used below and behind the wall are a critical part of the total wall structure.
A reinforced retaining wall is a structure containing three basic building materials - the block facing, the synthetic geogrid reinforcing materials, and the infill materials surrounding the geogrid layers
Soils and Soil Selection
Typical Friction Angle and Soil Unit Weights Chart
   

Retaining Wall Compaction
Proper placement and compaction of the infill soils are critical.
The most important step in getting proper compaction.
The consolidation zone runs from the back of the block back 3 ft (0.9 m) into the infill soil.
   

Water Management
The design and performance of most retaining walls are based on keeping the reinforced zone relatively dry.
Things to consider in our design:
Grading, Ground Water, and Concentrated Water Sources.
   
Build Patterned Walls with AB, AB Aztec and AB Europa Collections

Retaining Wall Patterns
All of the Allan Block Collections can be used to create a variety of pre-set and random patterned retaining walls.
Two and Three Course Patterns
Lite Patterns using the smaller blocks in the Collection.
   

Pattern Wall Construction
Excavate and Install Base Course
Install Geogrid
Install Course Pattern
Ending and Topping off Wall
   

Patterned Wall Construction Tips
Installing Reinforcement
Ending and Topping off the Retaining Wall
Curves and Corners
Stairs, Step-Ups and Tips for Patterned Walls
   
Building with AB Fieldstone

AB Fieldstone Gravity Wall Construction
Base Coursse and AB Fieldstone
Installing Wall Rock and Backfill Materials
Additional Courses for AB Fieldstone
Stepping up the Wall Base
   

AB Fieldstone Reinforced Wall Construction
Install Base Course for AB Fieldstone
Install Wall Rock and Backfill Materials
Compaction and Installation of Geogrid
Backfill & Compact with Additional Courses
   

Finishing an AB Fieldstone Wall with Caps
Filter Fabric Above Top Block / Below Cap
Capping Step-Downs
   

AB Fieldstone Construction Tips
Inside and Outside Curves with AB Fieldstone
AB Radius Chart for the Base Course of AB Fieldstone
Modifying Anchoring Units
   

AB Fieldstone Stepping Down
Creating a step down is similar to building an outside corner as it uses the same facing units that are manufactured with a textured side and has the same placement of the anchoring units.
When Stepping up the Wall Base is Needed
   

AB Fieldstone Stairs
Stairs can be designed with flowing curves or straight lines. Curved sidewalls create a softer, natural look. Straight sidewalls and corners o?er a crisp, traditional style. Building stairs requires careful planning and flexibility and will take extra time to design and build.
   

AB Fieldstone Parapets
How to Build a Parapet or Double Sided Wall
Using Dogbone for Interlocked Parapets
Standard Parapets, Wider Parapets and Curved Parapets
   
Construction Details with AB, AB Aztec, AB Metropolitan, and AB Europa Collections

Finishing Retaining Walls
Ending and Topping Retaining Walls
Building Step Downs
Building Turn-in Retaining Walls
   

Building Curves and Serpentine
Inside and Outside Curves
Building Tighter Curves
Working with Radii
AB Radius Chart for the Base Course
   

Building Corner
Inside and Outside Corners
Altering AB Corner Blocks for Different Setbacks
Installing Geogrid on Inside and Outside Corners
   

Proper Stair Construction for Retaining Walls
Stair Design
Stair Applications
Basic Stair Construction
Stair Tread Options
Ideas for Designing Stairways   Allan Block Video Logo
   

Building Terraces
It is often more aesthetically pleasing to replace one large retaining wall with two or more smaller terraced walls. Terraced walls can act as surcharges and may create global instability, therefore reinforcement may be necessary.
   

Building Water Applications
Retaining walls constructed in conditions where there is moving water (streams), standing water with wave action (lakes), or retention ponds are considered water applications.
Water applications must be evaluated and designed to fit the unique characteristics of the site. Consult with a local qualified engineer for design assistance.
   

Adding Fences, Railings and Gates
There are several options for installing fences and guide rails on top of an Allan Block retaining wall. The structure and wind loads of the materials used will determine the placement of the fence relative to the retaining wall and if additional reinforcement is required. Refer to the approved plans for construction details.
Sleeve-IT
   

Lighting for Retaining Walls
Lighting brings new possibilities to any landscape. Add a dramatic look with ground mounted lighting or illuminate stairways and pathways with recessed lighting. Allan Block walls with decorative lighting fixtures provide not only a distinctive design, but adds safety and security to the landscape.
   

Design Details for Allan Block Retaining Walls
Allan Block has a library of design details - cross section drawings to assist the design community in efficiently creating professional documents for our retaining walls and fence system.
Typical Details, Drainage Details, Fence Details, Water Applications Details, AB Fieldstrone Details, and Additional Details
   

Construction and Inspection Checklist
Review Wall Design Plans For:
Compliance of Site to Latest Site Plan
Review of Reported Soil Conditions with On-Site Soils Engineer
Review of Above Grade Water Management with Project Civil Engineer
   

Material Estimation Worksheet
Examples for Material Estimation including:
Geogrid
Drain Pipe
Infill Soils
   

Define Terms
Define Terms:
Base Material, Reinforced Zone, Consolidation Zone, Compaction Zone, Geogrid, Infill Soils, Drain Pipe, and Wall Rock.
   

Estimating Chart (Geogrid & No-Fines)
Surcharge Cases
Design Parameters
Geogrid
   
Specifications

Wall Specifications
Section 1 General
Section 2 Materials
Section 3 Wall Construction
   

Geogrid Specifications
Section 2 Part 1 General
Part 2 Materials
Part 3 Wall Construction
   

Leed Chart
What is LEED?
How Can Allan Block Products Help Your Project Achieve LEED Credits?
LEEDs Charts
   

Glossary
Glossary
Glossary of Terms
   
Charts and Tables

Standard Product Specifications Chart
Table 1.2 - Chart
   

Gravity Wall Heights Chart
Table 1.3 - Chart
   

Soils Chart for Retaining Walls
Table 2.1 - Chart
   

AB Setback Chart
Table 2.2 - Chart
   

Typical Friction Angle and Soil Unit Weights Chart
Table 3.1 - Chart
   

AB Radius Chart for the Base Course
Table 6.1 - Chart
   

Estimating Chart (Geogrid & No-Fines)
Surcharge Cases
Design Parameters
Geogrid
   

Leed Chart
What is LEED?
How Can Allan Block Products Help Your Project Achieve LEED Credits?
LEEDs Charts
   

Retaining Wall Planning

Develop an accurate understanding of the jobsite before beginning any design, engineering, or construction on a project.

Site Geometry

Develop an accurate plan of existing physical features. Observe the soil type and condition, site geometry at the retaining wall location and immediate surroundings. Note the natural drainage patterns. Identify all physical features surrounding the proposed retaining wall location. Note key elevations, lot lines, utilities, structures, vegetation, etc. Conditions above and behind the wall will determine how high the retaining wall can go before reinforcement is needed.

Soils

The soils used below and behind the wall are a critical part of the total retaining wall structure.

Understanding the properties and characteristics of soils is key to building better walls. Different soil types will dictate the amount of time needed for Compaction, the amount of reinforcement required, and potentially the cost of the retaining wall.

Project Site Plan for proposed retaining wall

Note the site geometry above and below the proposed wall location.

Check the on-site soils carefully before beginning, and get a written identification of the soil type. A soils report from a local engineer will be required before a design and/or permit is issued for most retaining walls above 4 ft. (1.2 m). See the Soils Chart for a general classification of soils.

  • Soil conditions behind and below each retaining wall have a direct effect on the strength needed in that retaining wall. The pressure from behind the wall will vary substantially depending on the soil type. In general, a wall built in clay soils will require more reinforcement than a wall of the same height built in free draining sand or gravel soils.
  • Check the soil type and conditions at the base of each wall for adequate bearing pressure. The soil below a wall needs to be strong enough to support the weight of the wall resting on it. When moisture is present, extra precautions may be required to provide a stable base.
  • If the soils at the base of the wall have been disturbed - i.e. excavated and replaced - it is imperative that these soils are properly compacted before construction begins. It may be necessary to remove poorly compacted or soft, wet organic soils at the base and replace them with stable, well compacted soils prior to wall construction.
Soil Selection

If the on-site soils are of a very low quality, you should remove and replace them with better backfill material in the reinforced zone and the foundation area. The cost of removal will be offset by reduced reinforcement, faster compaction, and better long-term performance.

In the reinforced zone, the type of soil used will determine the amount of grid reinforcement needed. Heavy clays and organic soils are both unsuitable in the reinforced zone. Generally, any soil with a friction angle lower than 27° (Ref) or a plasticity index (PI) of greater than 20 should be removed and replaced. Soils with friction angles between 27° (Ref) and 31° (Ref) will require additional care, and attention to water management when placed and compacted. This will include extra inspections by an on-site engineer. See the Soils Chart for information on friction angles of soil

You must use infill soils that meet or exceed those specified in the engineered specifications and drawings. Have the soils tested before placing and compacting.

Water Management

Make a careful observation of the general drainage patterns at the site. Note the amount of area above the wall which will shed surface runoff toward the wall. Note the type of surface (i.e., paved surfaces, sodded areas, etc.) to determine the water flow and volume. Note any concentrated sources of water flow such as runoff from parking lots, roof drains and scuppers, drainage swales, creek beds, ground water, etc. Learn more about Water Management.

Grading

Develop a grading plan that routes water around the walls as much as the site will allow. Provide swales above and below the wall as required to accommodate water movement. Divert sources of concentrated water flow from the wall. Retaining wall designs must prevent the pooling of water above or below the wall.

Drainage

Proper drainage planning considers water flow and volume above, below, and behind the retaining wall.

  • Most Allan Block gravity walls (lower unreinforced walls) will drain adequately on their own.
  • If a large area sheds water to the wall (i.e., parking lot), added drainage will be necessary.
  • Concentrated sources of water must be planned for and managed.
  • Reinforced walls will need added drainage for the backfill zone and the wall base.
  • Major wall structures, roadway and municipal projects, and walls built in extreme rainfall or wet environments will need a thorough hydrology analysis prior to construction.
Surcharges

Any added weight above the wall is called a “surcharge”. Parking lots, swimming pools, and driveways are common surcharges. Light duty surcharges are designed at 100 psf (4.7 kPa). Heavier commercial surcharges (like trucks), run 250 psf (12 kPa) and up. More concentrated line loads may also be a factor (such as building foundations). Engineering is required in each situation.

Reference 1
Parking Lot Drainage from a retaining wall application

Parking Lot Drainage



Retaining Wall Drainage with large storm water pipe

Retaining Wall Drainage



Surcharge example for a retaining wall application

Slopes

Slopes are measured “run to rise”. A three-to-one slope goes back 3 and up 1.

Slopes Above

Slopes above the wall add more pressure and will require more mass to resist movement. Engineering is required.

Slopes Below

Slopes below the wall may create an unstable foundation. Check with local building codes for length of bench that may be required. Engineering is required.



Slope Above a retaining wall application


Slopes Below a retaining wall application
Setback

The amount the wall leans into the hill is called “setback”. AB units come in multiple setbacks. Bigger setbacks provide better leverage and require less reinforcement. For taller walls use a story pole and level to check for proper setback. Setbacks increase when walls are built with radii. Comply with construction tolerances which are found in the AB Spec Book or approved construction plans.



Note: Walls designed with a 12° (Ref) setback require more space than 6° (Ref) or 3° (Ref) systems, but will be more stable. You may give up ground, but the final factors of safety are higher.

Setback on a retaining wall example
Setback with story pole on a retaining wall
Global Stability

Global stability is an engineering analysis of the overall balance of a slope or hillside. Walls built on hillsides may affect this balance and stability. Cuts into a hillside will steepen the effective slope and shift the balance of the hill, thereby reducing stability. Walls built on top of slopes have the same effect. Engineering is required.

What to consider when assessing global stability:

  • Surcharges / Terraced Walls
  • Slopes
  • Soil Properties
  • Water
Reference 1    Reference 18   

Global Stability

Retaining Wall global stability example