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Safety Cue
Task-specific safety guidance for ordinary work hazards.
Chapter 12
Build a Small Segmental Retaining Wall
Build one small segmental gravity retaining-wall practice section within approved height, soil, surcharge, setback, and manufacturer limits, with a level first course, correct bond and setback, drainage aggregate, controlled backfill, and documented height.
Field Cue System
These cues appear at the point of work. They identify safety, code, manufacturer, and measurement issues before they become rework or wall failure.
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Critical Safety Cue
Serious injury, wall collapse, or major damage is possible.
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Field Safety Cue
Practical work-area safety: excavation, footing, and equipment travel.
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Code Alert
Local requirements vary. Verify permit, setback, and inspection rules.
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Manufacturer Cue
Follow product-specific instructions for block units and geogrid.
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Measurement Cue
Level, setback, elevation, and course-height guidance.
Job Overview
This chapter qualifies you to build one small segmental gravity retaining-wall practice section that remains within the approved nonengineered height, soil, surcharge, and setback limits stated by the wall design or the manufacturer's published height table. The finished work product is one wall section with an accepted leveling pad, a level and buried first course, correctly staggered and set-back courses, drainage aggregate placed behind the wall as it rises, controlled and compacted backfill, geogrid installed exactly where the design specifies it, and a documented final height and alignment.
You will confirm the wall qualifies for nonengineered construction, excavate and compact a leveling pad, set and level the first course, build successive courses with the required setback and bond, place drainage aggregate and backfill in controlled lifts, install geogrid where required, and inspect the completed wall before it is capped in Chapter 14.
This chapter depends directly on the site readiness and drainage findings from Chapters 1 and 4. Chapter 13 installs the wall's continuous drainage pipe and outlet system into the drainage aggregate you place here, and Chapter 14 caps the wall you build in this chapter. A retaining wall built without a level first course, correct setback, and controlled backfill cannot be corrected by drainage work or a cap installed afterward.
Skills You Will Demonstrate
- HC-067 — Prepare the wall base, including excavation, subgrade compaction, and a compacted leveling-pad aggregate lift at the approved elevation and slope.
- HC-068 — Set the first block course to line, level, and required buried depth at the controlling low point of the wall.
- HC-069 — Maintain level across each course using a 4-foot level and correct high or low units before proceeding to the next course.
- HC-070 — Stagger wall units so vertical joints do not align between adjacent courses, maintaining the manufacturer's required setback and bond pattern.
- HC-071 — Backfill behind the wall with drainage aggregate and retained-soil backfill in compacted lifts, without displacing wall units, geogrid, or fabric.
- HC-072 — Inspect wall alignment, including line, curve, level, setback, bond, drainage continuity, and stability, and document the results.
Where This Skill Fits
A segmental gravity retaining wall holds back soil using the weight, setback, and interlock of the units themselves rather than embedded reinforcement, except where geogrid is specifically required by the design. Every requirement in this chapter — a level first course buried to the specified depth, consistent setback between courses, staggered vertical joints, and controlled, compacted backfill — exists because a small error at the base of the wall is magnified by every course built on top of it, and because uncontrolled or uncompacted backfill places pressure the gravity system was not designed to resist.
This chapter also teaches the stop-work discipline that separates a legitimate small gravity wall from a wall that requires engineering: a wall supporting a structure, driveway, steep slope, fence, pool, or road, or a wall exceeding the manufacturer's nonengineered height limit, is not built under this chapter's procedure.
Scope and Intended Use
This chapter covers:
- confirming the wall height, retained height, slope, surcharge, soil, foundation, setback, and drainage conditions qualify for nonengineered construction
- locating utilities and laying out the wall face, ends, curves, and excavation limits
- excavating and compacting the leveling-pad subgrade and installing a compacted aggregate leveling pad
- setting, leveling, and burying the first block course
- installing successive courses with the manufacturer's required setback, bond, and staggered vertical joints
- placing drainage aggregate behind the wall as it rises
- compacting reinforced and retained backfill in approved lifts using equipment appropriate to distance from the wall
- installing geogrid where the design specifies elevation and orientation
- inspecting and documenting base, first course, bond, setback, drainage, backfill, geogrid, alignment, and stability
This chapter does not authorize the learner to:
- build a wall supporting a structure, driveway, steep slope, fence, pool, road, or other surcharge not identified and approved on the wall design
- exceed the manufacturer's published nonengineered gravity-wall height limit for the block system in use
- omit geogrid where the design or manufacturer height table requires it, or substitute fabric, mesh, or an unapproved reinforcement material
- cap the wall or open it to backfill loading beyond the approved lift sequence before Chapter 13 drainage and Chapter 14 capping are complete
Any wall condition identified during this chapter as exceeding nonengineered limits must be referred to an engineer before construction proceeds.
Reference Conventions
Establish these references before construction begins, and record them on the wall construction record.
| Term | Definition |
|---|---|
| Wall height | The vertical distance from the top of the leveling pad to the top of the last block course, excluding the cap, measured at the controlling high point of the wall |
| Retained height | The vertical distance from the top of the leveling pad to the finished grade behind the wall, which controls the soil pressure the gravity system must resist |
| Setback | The horizontal distance each course is placed behind the course below it, as specified by the block manufacturer, which gives the wall its batter and stability |
| Buried depth | The portion of the first course placed below finished grade in front of the wall, as specified by the manufacturer or design |
| Surcharge | Any load behind the wall beyond the retained soil itself, including a structure, driveway, slope, fence, pool, or road |
| Reinforced backfill zone | The backfill zone directly behind the wall, extending to the limit specified by the design, where drainage aggregate and any geogrid are placed |
Wall Scope Record
Before excavation begins, record the wall scope directly on the construction record:
Block system: ______ Manufacturer nonengineered height limit: ______ Design wall height: ______ Design retained height: ______
Surcharge present: ______ (None / Structure / Driveway / Slope / Fence / Pool / Road) Setback from property line: ______ Geogrid required: ______ (Yes / No)
Date started: ____________ Builder name: ____________
Prerequisites
- A completed Chapter 1 hardscape-readiness plan and Chapter 4 excavation covering the wall location, or equivalent documented site and subgrade findings
- A wall design or manufacturer nonengineered height table confirming the wall qualifies for construction under this chapter without an engineer
- A submitted and confirmed utility-locating response for the full wall excavation area
- Property owner or authorized-representative permission to excavate, place backfill, and operate a plate compactor on site
- Identification of the contact for an engineer, in case the wall is found during layout or excavation to exceed nonengineered limits
Common Field Fundamentals
Every segmental gravity wall in this book depends on the same sequence: confirm nonengineered scope, prepare an accepted base, set and level the first course, build successive courses with correct setback and stagger, place drainage aggregate and controlled backfill as the wall rises, install geogrid exactly where specified, and inspect the finished wall as one system rather than as blocks stacked on soil.
Base preparationExcavation, subgrade compaction, compacted leveling-pad aggregate
First courseLevel, line, buried depth, controlling low point
Course constructionSetback, stagger, bond, sweeping unit tops clean
Drainage and backfillDrainage aggregate, compacted lifts, geogrid where required
Stop-Work Conditions
This chapter requires the builder to halt construction, rather than continue building, whenever a condition exceeds the approved nonengineered scope. These conditions must be referred to an engineer before wall construction resumes.
HC-067 – HC-072
Retaining Wall Construction Qualification
Small Segmental Retaining Wall Construction
A. Finished Project Specification
Deliverable: one small segmental gravity retaining-wall practice section built within the approved nonengineered height, soil, surcharge, and setback limits, with a compacted leveling pad, a level and correctly buried first course, successive courses built to the manufacturer's specified setback and staggered bond, drainage aggregate placed behind the wall as it rises, geogrid installed where the design requires it, retained backfill compacted in controlled lifts, and a documented final height, alignment, and stability inspection.
B. Wall Construction Record Schedule
| Record | Required Content | Source |
|---|---|---|
| Wall scope confirmation | Design height, retained height, surcharge, soil, setback, and confirmation of nonengineered scope | Wall design or manufacturer height table |
| Utility locate confirmation | Locate ticket number, response date, marked utilities present | Utility-locating service |
| Layout record | Wall face line, ends, curves, and excavation limits | Field layout |
| Base preparation record | Excavation depth, subgrade compaction, leveling-pad aggregate type, lift thickness, compaction passes | Field construction |
| First-course record | Level readings, line position, buried depth at each check point | Field construction |
| Course-by-course record | Setback, bond, stagger, and level for each course installed | Field construction |
| Drainage and backfill record | Drainage aggregate placement, backfill lift thickness, compaction equipment and passes by distance from wall | Field construction |
| Geogrid record | Elevation, orientation, and embedment length for each geogrid layer installed, or confirmation that geogrid is not required | Wall design and field installation |
| Final inspection | Final height, alignment, level, setback, drainage continuity, and stability findings | Field inspection |
C. Governing Document Checklist
- Wall design or manufacturer height table: confirms nonengineered scope, setback, buried depth, and geogrid requirements.
- Site and drainage plan: confirms wall location, retained height, and drainage outlet.
- Utility records: confirms utility locations before excavation.
- Permit conditions: confirms required permits and inspections for the wall's design height.
D. Acceptance Standards
| Check | Standard |
|---|---|
| Nonengineered scope | Design wall height and retained height are at or below the manufacturer's published nonengineered limit, and no unapproved surcharge is present |
| Leveling pad | Compacted aggregate leveling pad is placed at the approved elevation, thickness, and level or slope stated by the design |
| First course | Level front-to-back and side-to-side on every unit, buried to the manufacturer's specified depth, and aligned to the layout line or curve |
| Course setback and bond | Each course is set back from the course below it by the manufacturer's specified amount, with vertical joints staggered and not aligned between adjacent courses |
| Drainage aggregate | Free-draining aggregate is placed continuously behind the wall as it rises, free from fine-soil contamination |
| Geogrid | Installed at the exact elevation, orientation, and embedment length specified by the design, with no substitution of fabric or mesh |
| Backfill compaction | Backfill is placed and compacted in lifts appropriate to the material, using hand or lightweight equipment near the wall face and standard equipment only beyond the manufacturer's specified distance |
| Final alignment and stability | Wall face is straight or smoothly curved as designed, courses are level, and the wall shows no rocking, bulging, or displaced units |
E. Preparation — Confirm Scope and Locate Utilities
- Review wall height, retained height, slope, surcharge, soil, foundation, setback, curve, drainage, reinforcement, property-line, and permit limits. Record each value from the wall design or manufacturer height table on the Wall Scope Record.
- Confirm the wall qualifies for the approved nonengineered practice scope. Compare the recorded design height and retained height against the manufacturer's published nonengineered limit for the block system in use.
- Stop work for walls supporting structures, driveways, steep slopes, fences, pools, roads, or unknown surcharge without design. Refer any such condition to an engineer and record the referral before proceeding.
- Locate utilities. Submit or confirm the utility-locating request for the full wall and backfill excavation area.
F. Layout and Base Excavation
- Lay out wall face, ends, curves, and excavation limits. Mark the controlling wall face line, end conditions, and any curves using the layout methods from Chapter 3, and mark excavation limits that extend beyond the wall face to accommodate the leveling pad and drainage zone.
- Excavate for leveling pad and drainage zone. Excavate to the depth specified by the wall design, extending behind the wall face to the width of the specified drainage zone.
- Remove organic and unsuitable soil. Remove roots, organic material, debris, and any soft or previously disturbed soil found in the excavation.
- Compact the subgrade. Compact the exposed subgrade using the plate compactor before placing leveling-pad aggregate.
G. Leveling Pad and First Course
- Install approved base aggregate in compacted lifts. Place the leveling-pad aggregate specified by the wall design in lifts not exceeding the specified maximum lift thickness.
- Screed and compact the leveling pad. Screed the aggregate to the elevation and slope specified by the design, then compact with the plate compactor.
- Set the first block at the controlling low point. Place the first unit at the wall's lowest finished-grade point, so remaining units step up from a confirmed low reference.
- Level it front-to-back and side-to-side. Check with the 4-foot level in both directions and adjust the leveling-pad aggregate beneath the unit until level is achieved.
- Set additional first-course units tightly or at specified joints. Continue along the layout line, maintaining the manufacturer's specified joint condition between units.
- Check line, curve, and level after every few units. Use the mason's line and 4-foot level at regular intervals rather than only at the end of the course.
- Bury the required portion of the first course. Confirm the buried depth in front of the wall matches the manufacturer's specified minimum before backfilling in front of the units.
- Sweep unit tops clean. Remove aggregate, soil, and debris from the top of the first course before placing the next course.
H. Successive Courses, Drainage, and Backfill
- Install the next course with required setback and bond. Set each unit back from the course below by the manufacturer's specified setback distance, following the specified bond pattern.
- Stagger vertical joints. Offset each course so vertical joints do not align with the course directly below.
- Place drainage aggregate behind the wall as it rises. Add drainage aggregate to the reinforced backfill zone after each course is set, keeping the aggregate free of fine-soil contamination.
- Compact reinforced or retained backfill in approved lifts using equipment appropriate to distance from the wall. Compact each lift before placing the next, using a hand tamper or lightweight compactor near the wall face.
- Do not push heavy compaction equipment directly against the wall. Maintain the manufacturer's specified minimum distance for standard compaction equipment.
- Install geogrid where specified, at the required elevation and orientation. Place geogrid at the exact course elevation and orientation shown in the wall design, extending it to the specified embedment length into the backfill.
- Maintain wall batter, alignment, and course level. Recheck the mason's line and 4-foot level after each course and correct any drift before continuing.
- Stop at the approved height. Complete the final course at the design wall height and confirm it does not exceed the manufacturer's nonengineered limit.
I. Final Inspection and Documentation
- Inspect base, first course, bond, setback, drainage, backfill, geogrid, alignment, and stability. Walk the full wall length and confirm each item against the Acceptance Standards table.
- Document wall limitations and inspections. Record the final wall height, retained height, setback measurements, geogrid record, and inspection findings on the Wall Construction Record.
Common Site Inspection
Review every completed wall section using the same checks regardless of wall length or curve.
- Scope check: confirm the wall's design height and retained height remain within the manufacturer's nonengineered limit and no unapproved surcharge is present.
- Base check: confirm the leveling pad is compacted at the correct elevation and slope.
- First-course check: confirm every unit is level, correctly buried, and aligned to the layout line or curve.
- Course check: confirm setback, bond, and staggered vertical joints are consistent through every course.
- Drainage and backfill check: confirm drainage aggregate is continuous and backfill is compacted in lifts without displacing wall units or geogrid.
- Stability check: confirm the finished wall shows no rocking, bulging, or displaced units before Chapter 13 drainage work begins.
Complete the Wall Construction Record in the Inspection Checklist section below before beginning Chapter 13.
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Failure Points and Troubleshooting
Cleanup
This chapter ends with a stable, level, correctly backfilled wall section and a completed construction record, not a wall built from memory.
- Remove excess aggregate, soil, and debris from the work area and adjacent surfaces
- Store unused block units, drainage aggregate, and geogrid protected from weather and contamination for use in later wall sections
- Photograph the completed wall face, drainage aggregate, and any geogrid layers before they are concealed by further backfill or capping
- File the Wall Construction Record with the wall design, manufacturer height table, and utility locate ticket
- Retain the completed wall record for reference in Chapter 13 drainage installation and Chapter 14 capping
Field Terms
- Wall Height
- The vertical distance from the top of the leveling pad to the top of the last block course, excluding the cap.
- Retained Height
- The vertical distance from the top of the leveling pad to the finished grade behind the wall.
- Setback
- The horizontal distance each course is placed behind the course below it, giving the wall its batter.
- Buried Depth
- The portion of the first course placed below finished grade in front of the wall.
- Surcharge
- Any load behind the wall beyond the retained soil itself.
- Reinforced Backfill Zone
- The backfill zone directly behind the wall where drainage aggregate and geogrid are placed.
- Leveling Pad
- The compacted aggregate base beneath the first course that establishes the wall's starting elevation and level.
- Gravity Wall
- A retaining wall that resists soil pressure through the weight and setback of its own units rather than embedded reinforcement.
- Geogrid
- A specified soil-reinforcement material installed at a defined elevation and orientation to extend the wall's effective mass into the backfill.
- Bond Pattern
- The staggered arrangement of vertical joints between courses that prevents a continuous joint line from running through the wall.
Skill Check
- What conditions require a segmental retaining wall to be referred to an engineer rather than built under this chapter's procedure?
- Why must the first course be checked for level after every few units rather than only at the start and end of the course?
- What is the difference between wall height and retained height, and why does retained height affect backfill and drainage requirements?
- Why must vertical joints be staggered between courses instead of aligned?
- Why is heavy compaction equipment prohibited directly against the wall face, and what is used instead?
- What happens to drainage performance if fine soil contaminates the drainage aggregate behind the wall?
- Where does geogrid go, and why must its elevation and orientation match the design exactly rather than an estimated position?
- What must be confirmed before backfill is compacted in the lift directly above a newly installed geogrid layer?
- Why is burying the first course to the manufacturer's specified depth necessary for wall stability?
- Why must this chapter's wall be inspected and documented before Chapter 13 drainage work begins?
Competency Rubric
| Competency | Independent Pass Standard | Not Demonstrated | With Assistance | Independently |
|---|---|---|---|---|
| HC-067 | Excavates, compacts the subgrade, and installs a compacted leveling-pad aggregate lift at the approved elevation and slope | |||
| HC-068 | Sets and levels the first block course at the controlling low point, front-to-back and side-to-side, buried to the specified depth | |||
| HC-069 | Checks and maintains level across each course using a 4-foot level, correcting high or low units before proceeding | |||
| HC-070 | Installs each course with the manufacturer's specified setback and staggered vertical joints, with no aligned joints between adjacent courses | |||
| HC-071 | Places drainage aggregate and compacts retained backfill in approved lifts, using equipment appropriate to distance from the wall, without displacing units or geogrid | |||
| HC-072 | Inspects and documents base, first course, bond, setback, drainage, backfill, geogrid, alignment, and stability for the completed wall |
Mark one column per competency. Only Demonstrated Independently awards the competency; Demonstrated with Assistance authorizes additional supervised practice but does not complete the requirement.
Inspection Checklist — Wall Construction Record
| Record | Finding | Deficiency (if any) | Prerequisite / Corrective Action | Status |
|---|---|---|---|---|
| Wall scope confirmation | ||||
| Utility locate | ||||
| Layout record | ||||
| Base preparation | ||||
| First-course level and burial | ||||
| Course setback and bond | ||||
| Drainage aggregate and backfill | ||||
| Geogrid installation | ||||
| Final alignment and stability |
Final wall height: ______ Final retained height: ______ Inspection result: ______ (Accepted / Corrections required)
Date: ____________ Builder name: ____________ Reinspection date (if applicable): ____________
Performance Check
With the wall constructed and every record on the Wall Construction Record completed, review the finished wall against the Acceptance Standards table and confirm that the wall remains within nonengineered scope, the leveling pad and first course are level and correctly buried, setback and bond are consistent through every course, drainage aggregate is continuous, geogrid is installed exactly as specified where required, backfill is compacted in controlled lifts, and the finished wall shows no rocking, bulging, or displaced units. If any item is incomplete or a deficiency remains unresolved, correct it and reinspect the affected record before beginning Chapter 13.
Project Closeout
You have completed the twelfth chapter in the hardscaping sequence: building a small segmental retaining wall. This chapter required you to prepare the wall base (HC-067), set the first block course (HC-068), maintain level (HC-069), stagger wall units (HC-070), backfill behind the wall (HC-071), and inspect wall alignment (HC-072).
You now have a stable, level, correctly bonded and set-back segmental retaining wall section with drainage aggregate placed behind it, backfill compacted in controlled lifts, and geogrid installed where the design required it. That wall carries directly into the next chapter: installing a continuous drainage pipe and lawful outlet into the drainage aggregate zone you established here.
Retain the completed Wall Construction Record, wall design or manufacturer height table, and utility locate ticket. You will reference this exact wall throughout Chapters 13 and 14.