Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Site Retaining Walls
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### IBC Section 1807 and most jurisdictions require a permit and an engineered design for retaining walls retaining more than 4 ft of unbalanced backfill measured from the bottom of the footing to the top of the wall, and for any wall of any height that carries a surcharge, supports a slope above, or retains water — these conditions add load or remove the simplifying assumptions that gravity-wall charts rely on. {note}
+### The requirement for an engineered, PE-stamped design shall be determined and specified for each retaining wall based on its height, surcharge, backfill slope, and water retention.
+
```datasheet
label: Engineered (PE-Stamped) Design Required
…15 unchanged lines
### The engineered design shall demonstrate adequate external, internal, and global stability for the wall and the loads acting on it.
−### The Contractor shall not substitute a manufacturer's standard gravity-wall chart for an engineered design where an engineered design is required. {note}
+### The Contractor shall not substitute a manufacturer's standard gravity-wall chart for an engineered design where an engineered design is required.
## Global Stability {toc}
…50 unchanged lines
### A wall founded above the frost line in a frost-susceptible soil heaves and settles seasonally, opening joints and racking the wall, so the foundation must extend below the local frost depth. {note}
+### The wall foundation, leveling pad, or footing shall be embedded below the local frost depth in frost-susceptible soils, and not less than the embedment shown on the wall design.
+
+### The minimum embedment of the bottom of the wall below the finished grade at the toe shall be the greater of the design value or a minimum of one-tenth the exposed wall height, unless the engineered design establishes a different value.
+
```datasheet
label: Foundation Embedment Below Finished Grade at Toe
…8 unchanged lines
```
−### The wall foundation, leveling pad, or footing shall be embedded below the local frost depth in frost-susceptible soils, and not less than the embedment shown on the wall design.
+### Embedment shall be increased where the wall toes out onto a slope, because a wall fronting a descending slope has less passive resistance and a shallower path to a global failure surface.
−### The minimum embedment of the bottom of the wall below the finished grade at the toe shall be the greater of the design value or a minimum of one-tenth the exposed wall height, unless the engineered design establishes a different value.
−
−### Embedment shall be increased where the wall toes out onto a slope, because a wall fronting a descending slope has less passive resistance and a shallower path to a global failure surface. {note}
−
## Surcharge from Adjacent Structures {toc}
### A surcharge is any load applied to the soil behind the wall in addition to the soil weight — a building footing, a roadway, a parking area, a stockpile, or construction equipment — and an unaccounted surcharge is a frequent cause of overstress and failure. {note}
+### The wall design shall account for every surcharge that acts within the zone of influence behind the wall, including sloped backfill, traffic and parking loads, adjacent building foundations, and construction loading.
+
```datasheet
label: Surcharge Condition Behind Wall
…8 unchanged lines
```
−### The wall design shall account for every surcharge that acts within the zone of influence behind the wall, including sloped backfill, traffic and parking loads, adjacent building foundations, and construction loading.
−
### The Contractor shall not operate heavy equipment or place stockpiles within the zone of influence behind a wall during or after construction unless the wall is designed for that surcharge.
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### A gravity SRW wall resists overturning by its own mass and is economical to roughly 3 to 4 ft of exposed height; above that, geogrid reinforcement extends the same units into a mechanically stabilized earth mass that can reach much greater heights; a cast-in-place cantilever wall is used where reinforcement cannot extend behind the wall or where a thin footprint is required; and gravity walls of mass concrete, gabions, or boulders suit specific site and appearance conditions. {note}
+### The wall type shall be as shown on the contract drawings and confirmed by the engineered wall design.
+
```datasheet
label: Retaining Wall Type
…9 unchanged lines
```
−### The wall type shall be as shown on the contract drawings and confirmed by the engineered wall design.
−
### Where the Contractor proposes an alternative wall type, it shall be supported by an engineered design meeting the same performance requirements and approved by the Engineer of Record.
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### The exposed height — the vertical face from the finished grade at the toe to the top of the wall — together with the embedment, sets the total design height and governs the wall type and the reinforcement. {note}
+### The exposed wall height shall be as shown on the wall profile.
+
```datasheet
label: Maximum Exposed Wall Height
…8 unchanged lines
```
−### The exposed wall height shall be as shown on the wall profile.
−
### Where the exposed height varies along the wall, the design and the geogrid layout shall be developed for the controlling (tallest) section and stepped down as the height decreases.
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### Batter is the backward lean of the wall face into the retained soil, and it improves stability by directing the resultant of the wall weight back toward the heel; segmental walls achieve batter through the setback built into each course of units. {note}
+### The wall face shall be constructed to the batter shown on the design, established by the unit setback for segmental walls or by the formed face for cast-in-place walls.
+
```datasheet
label: Wall Face Batter (Setback)
…8 unchanged lines
```
−### The wall face shall be constructed to the batter shown on the design, established by the unit setback for segmental walls or by the formed face for cast-in-place walls.
−
### The batter shall be maintained uniformly course to course, and shall be checked as the wall rises so that drift does not accumulate.
−# Materials {toc}
+# Segmental Retaining Wall Units {toc}
−## Segmental Retaining Wall Units {toc}
+## SRW units shall conform to ASTM C1372. {note}
−### SRW units shall conform to ASTM C1372. {note}
+## SRW units shall have a minimum net-area compressive strength of 3000 psi, increased where severe weathering exposure requires.
```datasheet
…7 unchanged lines
```
+## SRW units shall meet the maximum water absorption of ASTM C1372 for the weathering region of the project.
+
```datasheet
label: SRW Unit Maximum Water Absorption
…5 unchanged lines
```
−### SRW units shall have a minimum net-area compressive strength of 3000 psi, increased where severe weathering exposure requires.
+## Units shall be sound, free of cracks and chips that impair structural integrity or appearance, and consistent in dimension within the ASTM C1372 tolerances so courses seat uniformly.
−### SRW units shall meet the maximum water absorption of ASTM C1372 for the weathering region of the project.
+## Units shall provide the design connection capacity to the geogrid where the wall is reinforced, verified by ASTM D6638 testing of the specific unit-and-geogrid combination.
−### Units shall be sound, free of cracks and chips that impair structural integrity or appearance, and consistent in dimension within the ASTM C1372 tolerances so courses seat uniformly.
+# Concrete and Reinforcing (Cast-in-Place and Gravity Concrete Walls) {toc}
−### Units shall provide the design connection capacity to the geogrid where the wall is reinforced, verified by ASTM D6638 testing of the specific unit-and-geogrid combination.
+## Cast-in-place cantilever and mass concrete gravity walls shall be constructed under [[sync/cast-in-place-concrete]], and the reinforcing steel shall be detailed and placed under [[sync/concrete-reinforcement]]. {note}
−## Concrete and Reinforcing (Cast-in-Place and Gravity Concrete Walls) {toc}
+## Cast-in-place concrete shall achieve the specified compressive strength shown on the wall design and shall meet the durability requirements for soil and weather exposure under [[sync/cast-in-place-concrete]].
−### Cast-in-place cantilever and mass concrete gravity walls shall be constructed under [[sync/cast-in-place-concrete]], and the reinforcing steel shall be detailed and placed under [[sync/concrete-reinforcement]]. {note}
−
```datasheet
label: Cast-in-Place Wall Concrete Compressive Strength
…9 unchanged lines
```
+## Reinforcing steel shall conform to ASTM A615 of the grade shown on the design, and shall be placed with the cover and at the locations shown.
+
```datasheet
label: Reinforcing Steel Grade
…5 unchanged lines
```
−### Cast-in-place concrete shall achieve the specified compressive strength shown on the wall design and shall meet the durability requirements for soil and weather exposure under [[sync/cast-in-place-concrete]].
+## The wall stem reinforcement shall be placed on the tension (retained-soil) face, and shall not be displaced toward the exposed face during placement, because cover error on the tension face directly reduces the wall's flexural capacity. {note}
−### Reinforcing steel shall conform to ASTM A615 of the grade shown on the design, and shall be placed with the cover and at the locations shown.
+# Geogrid Soil Reinforcement {toc}
−### The wall stem reinforcement shall be placed on the tension (retained-soil) face, and shall not be displaced toward the exposed face during placement, because cover error on the tension face directly reduces the wall's flexural capacity. {note}
+## Geogrid is the tensile reinforcement that converts a stack of facing units into a mechanically stabilized earth mass; it carries the lateral earth pressure into the soil through friction and pullout resistance, and its long-term design strength, after reduction for creep, installation damage, and durability, must meet the design demand. {note}
−## Geogrid Soil Reinforcement {toc}
+## Whether geogrid soil reinforcement is required for the retaining wall shall be specified, consistent with the engineered wall design.
−### Geogrid is the tensile reinforcement that converts a stack of facing units into a mechanically stabilized earth mass; it carries the lateral earth pressure into the soil through friction and pullout resistance, and its long-term design strength, after reduction for creep, installation damage, and durability, must meet the design demand. {note}
−
```datasheet
label: Geogrid Reinforcement Required
…29 unchanged lines
```
−### Geogrid reinforcement shall be the type and strength shown on the engineered wall design, with long-term design strength established per ASTM D6637 and the design reduction factors.
+## Geogrid reinforcement shall be the type and strength shown on the engineered wall design, with long-term design strength established per ASTM D6637 and the design reduction factors.
−### Geogrid length shall be not less than the value shown on the design, and not less than 0.6 times the total wall height; walls with a surcharge or a slope above commonly require lengths of 0.8 to 1.0 times the height or greater.
+## Geogrid length shall be not less than the value shown on the design, and not less than 0.6 times the total wall height; walls with a surcharge or a slope above commonly require lengths of 0.8 to 1.0 times the height or greater.
−### Geogrid vertical spacing shall not exceed the value shown on the design.
+## Geogrid vertical spacing shall not exceed the value shown on the design.
−### The geogrid-to-unit connection strength shall be verified for the specific unit-and-geogrid combination by ASTM D6638 testing, and shall meet the connection demand at every reinforcement level.
+## The geogrid-to-unit connection strength shall be verified for the specific unit-and-geogrid combination by ASTM D6638 testing, and shall meet the connection demand at every reinforcement level.
−### Geogrid shall be installed with the strong (machine) direction perpendicular to the wall face, because the design strength is the strength in that direction; geogrid laid with the strong direction parallel to the wall provides little reinforcement. {note}
+## Geogrid shall be installed with the strong (machine) direction perpendicular to the wall face, because the design strength is the strength in that direction; geogrid laid with the strong direction parallel to the wall provides little reinforcement.
−## Leveling Pad {toc}
+# Leveling Pad {toc}
−### The leveling pad is the prepared base course that the first course of units is set on; it spreads the wall load, establishes a level and true starting course, and a wall that starts out of level only gets worse as it rises. {note}
+## The leveling pad is the prepared base course that the first course of units is set on; it spreads the wall load, establishes a level and true starting course, and a wall that starts out of level only gets worse as it rises. {note}
+## The leveling pad shall be a compacted crushed-stone pad not less than 6 inches thick, or an unreinforced concrete pad where shown on the design.
+
```datasheet
label: Leveling Pad Type
…16 unchanged lines
```
−### The leveling pad shall be a compacted crushed-stone pad not less than 6 inches thick, or an unreinforced concrete pad where shown on the design.
+## The leveling pad shall extend beyond the front and back of the base units by the dimension shown on the design, and not less than 6 inches in each direction.
−### The leveling pad shall extend beyond the front and back of the base units by the dimension shown on the design, and not less than 6 inches in each direction.
+## The leveling pad shall be compacted and screeded level so the first course of units seats fully and uniformly without rocking.
−### The leveling pad shall be compacted and screeded level so the first course of units seats fully and uniformly without rocking.
+# Backfill {toc}
−## Backfill {toc}
+## Reinforced Fill {toc}
−### Reinforced Fill {toc}
+### The reinforced fill is the soil within the geogrid-reinforced zone behind an MSE wall; its friction angle and compaction are design assumptions, so it must be a free-draining granular soil placed and compacted exactly as the design requires. {note}
−#### The reinforced fill is the soil within the geogrid-reinforced zone behind an MSE wall; its friction angle and compaction are design assumptions, so it must be a free-draining granular soil placed and compacted exactly as the design requires. {note}
+### Reinforced fill within the geogrid zone shall be a free-draining granular soil meeting the gradation, friction angle, and plasticity limits of the engineered design.
```datasheet
…9 unchanged lines
```
−#### Reinforced fill within the geogrid zone shall be a free-draining granular soil meeting the gradation, friction angle, and plasticity limits of the engineered design.
+### Reinforced fill shall have a fines content (material passing the No. 200 sieve) not exceeding the design limit, commonly 15 percent or less, because excess fines reduce drainage and friction and raise the risk of moisture-driven failure.
−#### Reinforced fill shall have a fines content (material passing the No. 200 sieve) not exceeding the design limit, commonly 15 percent or less, because excess fines reduce drainage and friction and raise the risk of moisture-driven failure.
+### Reinforced fill shall be free of organics, debris, and particles larger than the design maximum, which can damage the geogrid during placement.
−#### Reinforced fill shall be free of organics, debris, and particles larger than the design maximum, which can damage the geogrid during placement.
+## Retained Fill {toc}
−### Retained Fill {toc}
+### The retained fill is the soil behind the reinforced zone or behind a gravity wall; it shall meet the parameters assumed in the design and shall not be a high-plasticity expansive clay placed against the wall.
−#### The retained fill is the soil behind the reinforced zone or behind a gravity wall; it shall meet the parameters assumed in the design and shall not be a high-plasticity expansive clay placed against the wall. {note}
+### Retained fill shall meet the soil parameters assumed in the wall design for friction angle, unit weight, and drainage.
−#### Retained fill shall meet the soil parameters assumed in the wall design for friction angle, unit weight, and drainage.
+### High-plasticity clays (USCS CH) and other expansive soils shall not be placed as retained fill directly behind the wall unless the design specifically accounts for their swelling pressure and reduced strength.
−#### High-plasticity clays (USCS CH) and other expansive soils shall not be placed as retained fill directly behind the wall unless the design specifically accounts for their swelling pressure and reduced strength.
+# Cap Units and Coping {toc}
−## Cap Units and Coping {toc}
+## The cap finishes the top of the wall, sheds water away from the wall face, and conceals the top course; an unsecured cap that is kicked off leaves the top course exposed and the wall looking unfinished. {note}
−### The cap finishes the top of the wall, sheds water away from the wall face, and conceals the top course; an unsecured cap that is kicked off leaves the top course exposed and the wall looking unfinished. {note}
+## Cap units shall be secured to the top course with a manufacturer-approved flexible concrete adhesive, or by the system's mechanical means, so they are not displaced by traffic, maintenance, or freeze-thaw.
```datasheet
…7 unchanged lines
```
−### Cap units shall be secured to the top course with a manufacturer-approved flexible concrete adhesive, or by the system's mechanical means, so they are not displaced by traffic, maintenance, or freeze-thaw.
+## The top of the wall shall be detailed to shed surface water away from the wall face and away from the drainage aggregate behind it.
−### The top of the wall shall be detailed to shed surface water away from the wall face and away from the drainage aggregate behind it.
−
# Drainage System {toc}
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### A free-draining aggregate zone immediately behind the wall, a perforated collector pipe at its base, a filter separation from the retained soil, and a positive outlet together keep the backfill drained and the pressure on the wall at the active (drained) value the design assumes. {note}
+### Every retaining wall shall be provided with a drainage system that prevents the buildup of hydrostatic pressure behind the wall, unless the wall is specifically designed to resist full hydrostatic load.
+
```datasheet
label: Wall Drainage System Provided
…6 unchanged lines
```
−### Every retaining wall shall be provided with a drainage system that prevents the buildup of hydrostatic pressure behind the wall, unless the wall is specifically designed to resist full hydrostatic load.
−
### The drainage system shall coordinate with [[sync/foundation-drainage]] where the wall drainage discharges into or shares the foundation drainage system.
…2 unchanged lines
### A clean, open-graded crushed stone immediately behind the wall face provides a free-draining zone that intercepts water before it reaches the retained soil and conveys it to the collector pipe. {note}
+### The drainage aggregate shall be a clean, open-graded crushed stone conforming to an ASTM D448 size such as No. 57 stone, with negligible fines so it drains freely.
+
```datasheet
label: Drainage Aggregate Gradation (ASTM D448)
…6 unchanged lines
```
+### The drainage aggregate zone shall be placed immediately behind the wall face and within the SRW unit cores where the units are hollow, in a continuous zone not less than 12 inches wide measured from the back of the units.
+
```datasheet
label: Drainage Aggregate Zone Width Behind Wall Face
…7 unchanged lines
```
−### The drainage aggregate shall be a clean, open-graded crushed stone conforming to an ASTM D448 size such as No. 57 stone, with negligible fines so it drains freely.
−
−### The drainage aggregate zone shall be placed immediately behind the wall face and within the SRW unit cores where the units are hollow, in a continuous zone not less than 12 inches wide measured from the back of the units.
−
### The drainage aggregate shall be placed and lightly compacted in lifts as the wall rises, kept free of fines and soil contamination, and not allowed to mix with the retained or reinforced fill.
…2 unchanged lines
### The perforated collector pipe at the base of the drainage aggregate gathers the intercepted water and carries it to an outlet; without a positive outlet the aggregate zone fills with water and the system fails. {note}
+### A perforated drainage pipe not less than 4 inches in diameter shall be placed at the base of the drainage aggregate zone, behind and at or below the bottom of the lowest course of units.
+
```datasheet
label: Perforated Drainage Pipe Diameter
…6 unchanged lines
```
+### The drainage pipe shall be laid with positive slope, not less than 1 percent, to outlets that daylight to grade, connect to the site storm drainage, or connect to the foundation drainage system.
+
```datasheet
label: Drainage Pipe Outlet Method
…6 unchanged lines
```
−### A perforated drainage pipe not less than 4 inches in diameter shall be placed at the base of the drainage aggregate zone, behind and at or below the bottom of the lowest course of units.
−
−### The drainage pipe shall be laid with positive slope, not less than 1 percent, to outlets that daylight to grade, connect to the site storm drainage, or connect to the foundation drainage system.
−
### Pipe outlets shall be located at the low points of the wall, spaced so no run is dead-ended, and shall be marked and protected so they are not buried or blocked.
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### A geotextile filter fabric between the drainage aggregate and the retained soil lets water pass into the aggregate while holding back the soil fines that would otherwise migrate in and clog the drainage path over time. {note}
+### A geotextile filter fabric shall separate the open-graded drainage aggregate from the adjacent finer soil, unless the adjacent fill is itself a clean, filter-compatible granular material.
+
```datasheet
label: Geotextile Filter Fabric Between Aggregate and Soil
…5 unchanged lines
```
−### A geotextile filter fabric shall separate the open-graded drainage aggregate from the adjacent finer soil, unless the adjacent fill is itself a clean, filter-compatible granular material.
−
### The filter fabric shall be lapped at all seams in the direction of water flow and carried up the full height of the drainage aggregate zone so soil cannot enter the aggregate over the top.
…5 unchanged lines
### IBC Section 1807 establishes the minimum static factors of safety of 1.5 against both sliding and overturning; bearing pressure shall not exceed the allowable bearing capacity. {note}
+### The wall shall be designed for a minimum static factor of safety against overturning of 1.5.
+
```datasheet
label: Minimum Factor of Safety — Overturning (static)
…7 unchanged lines
```
+### The wall shall be designed for a minimum static factor of safety against sliding of 1.5.
+
```datasheet
label: Minimum Factor of Safety — Sliding (static)
…7 unchanged lines
```
+### The maximum bearing pressure beneath the wall shall not exceed the allowable bearing capacity established by the geotechnical engineer.
+
+### The wall and the surrounding soil mass shall be designed for a minimum global (slope) stability factor of safety as established by the geotechnical engineer, commonly 1.5 for static conditions.
+
```datasheet
label: Minimum Factor of Safety — Global (Slope) Stability
…7 unchanged lines
```
−### The wall shall be designed for a minimum static factor of safety against overturning of 1.5.
−
−### The wall shall be designed for a minimum static factor of safety against sliding of 1.5.
−
−### The maximum bearing pressure beneath the wall shall not exceed the allowable bearing capacity established by the geotechnical engineer.
−
−### The wall and the surrounding soil mass shall be designed for a minimum global (slope) stability factor of safety as established by the geotechnical engineer, commonly 1.5 for static conditions.
−
### Where seismic loads govern, the seismic factors of safety shall be those required by the adopted code and the geotechnical report, which are lower than the static values because the seismic load is a short-duration event.
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### Geogrid placed at the wrong elevation, too short, with gaps in coverage, or with the weak direction perpendicular to the wall, does not reinforce the soil even though it appears installed; the layout on the design is exact, not approximate. {note}
+### Geogrid shall be placed at the elevations, lengths, and coverage shown on the engineered design, with the strong (machine) direction perpendicular to the wall face.
+
+### Geogrid shall be laid flat, pulled taut to remove slack and folds, staked or tensioned before the reinforced fill is placed over it, and connected to the units by the system's connection detail.
+
+### Equipment shall not run directly on the geogrid; fill shall be placed over the geogrid and tracked from the placed fill, not from the bare grid.
+
+### Geogrid shall provide continuous coverage across the wall length at each design elevation, with no unreinforced gaps except where the design specifically engineers partial coverage.
+
```datasheet
label: Geogrid Coverage Across Wall Length
…5 unchanged lines
```
−### Geogrid shall be placed at the elevations, lengths, and coverage shown on the engineered design, with the strong (machine) direction perpendicular to the wall face.
−
−### Geogrid shall be laid flat, pulled taut to remove slack and folds, staked or tensioned before the reinforced fill is placed over it, and connected to the units by the system's connection detail.
−
−### Equipment shall not run directly on the geogrid; fill shall be placed over the geogrid and tracked from the placed fill, not from the bare grid.
−
−### Geogrid shall provide continuous coverage across the wall length at each design elevation, with no unreinforced gaps except where the design specifically engineers partial coverage.
−
## Backfill Placement and Compaction {toc}
### The reinforced and retained fill carry the design soil parameters only if compacted to the design density at the design moisture, and over-compaction immediately behind the face can also push the wall out of alignment, so compaction near the face is done with light equipment. {note}
+### Reinforced and retained fill shall be placed in uniform lifts not exceeding the design lift thickness and compacted to the percent compaction shown on the design, commonly not less than 95 percent of Standard Proctor (ASTM D698) or as referenced to Modified Proctor (ASTM D1557) where the design so states.
+
```datasheet
label: Reinforced/Retained Fill Compaction
…18 unchanged lines
```
+### Within 3 feet of the wall face, compaction shall be performed with hand-operated equipment so the wall is not pushed out of alignment or batter.
+
```datasheet
label: Compaction Zone Behind Face — Light Equipment Only
…6 unchanged lines
```
−### Reinforced and retained fill shall be placed in uniform lifts not exceeding the design lift thickness and compacted to the percent compaction shown on the design, commonly not less than 95 percent of Standard Proctor (ASTM D698) or as referenced to Modified Proctor (ASTM D1557) where the design so states.
−
−### Within 3 feet of the wall face, compaction shall be performed with hand-operated equipment so the wall is not pushed out of alignment or batter.
−
### Heavy compaction equipment shall not operate within the zone behind the face reserved for light equipment, nor closer to the wall than the design permits.
…2 unchanged lines
## Drainage Installation Sequence {toc}
−### The drainage system shall be built up with the wall — the collector pipe set at the base, the drainage aggregate placed and kept clean as each course rises, and the filter fabric placed so soil cannot enter the aggregate — because the drainage cannot be added after the wall is backfilled. {note}
+### The drainage system shall be built up with the wall — the collector pipe set at the base, the drainage aggregate placed and kept clean as each course rises, and the filter fabric placed so soil cannot enter the aggregate — because the drainage cannot be added after the wall is backfilled.
### The Contractor shall place the perforated collector pipe at the base before backfilling begins, and shall place the drainage aggregate and filter fabric continuously as the wall rises.
…91 unchanged lines
## Where directed by the geotechnical engineer, survey monuments shall be installed on the wall and read at specified intervals to provide objective data on wall movement during the warranty period.