Direct answer
A retaining-wall takeoff divides the approved wall into courses and units, then separately measures buried course, base, drainage aggregate, pipe, reinforced backfill, geosynthetic layers, caps, corners, curves, and excavation.
What this calculation tells you
A system takeoff supports supplier quotations, delivery stages, excavation planning, and comparison of approved alternatives. It should preserve each wall segment, elevation, and selected product rather than reduce the project to face area.
Global, sliding, overturning, bearing, internal, seismic, surcharge, water, and connection performance require site and product-specific design.
Where it is used
Landscape construction
Plan units, caps, base, drainage, excavation, and backfill for approved low and engineered walls.
Civil construction
Coordinate reinforced-soil components and staged material delivery from design drawings.
Estimating
Separate visible units from buried, drainage, reinforcement, and earthwork scope.
Maintenance and repair
Quantify defined replacement zones after the failure cause and repair design are established.
When this guide helps
- The wall steps with sloping ground.
- Inside and outside curves change unit spacing.
- A fence or driveway adds surcharge near the wall.
- Groundwater or runoff reaches the retained soil.
Segment the wall by geometry
Record plan length at an explicit reference, base and top elevations, course heights, setbacks, curves, corners, steps, and product type. A centreline, front-face, and back-face length differ on curves.
Use whole course and unit rules for the selected system.
Measure the buried system
Base preparation, buried course, leveling pad, drain, drainage aggregate, filter or separation layer, reinforced fill, geosynthetic layers, and excavation can exceed the visible material effort.
Keep native backfill and imported specified material distinct.
Respect product-specific layout
Unit dimensions, batter, connection, minimum radius, corner units, cap lengths, and cutting rules vary. Current supplier information should drive package and accessory quantities.
Do not infer geosynthetic length or spacing from wall height alone.
Quantity follows stability design
Soil properties, water, slope, surcharge, seismicity, foundations, utilities, global stability, permits, and construction sequence require qualified assessment.
- Provide drainage an outlet.
- Keep wall segments traceable.
- Verify field conditions before ordering all stages.
Worked case: rectangular face
Wall 12 m long, 1.2 m high, module 0.4 × 0.2 m.
Courses = 6; units/course = 30; base units = 180; with 5% = 189.
Entered face takeoff is 189 units.
Corners, batter, caps and buried course are separate.
Reproduce this worked caseOpen Segmental Retaining Wall Block Calculator
Worked case: add buried course
One additional full buried course adds 30 units before allowance.
Base becomes 210; with 5% = 220.5, round 221.
The entered buried-course convention adds 32 purchased units after rounding.
Actual embedment follows site/design requirements.
Reproduce this worked caseOpen Segmental Retaining Wall Block Calculator
segmental retaining-wall units: compare assumptions, not just answers
Drainage aggregate, pipe, geogrid, excavation and soil conditions require distinct models and engineered design where applicable.
| Field scenario | Changed input | Calculated consequence |
|---|---|---|
| Visible 6 courses | 5% | 189 |
| +buried course | 7 courses | 221 |
segmental retaining-wall units: calculation checklist
- Course/module actual
- Buried course explicit
- Corners/caps separate
- Drainage quantities included
- Design approval
Practical questions
Frequently asked questions
Why count a buried course?
Many systems require units below finished grade as part of the approved base and embedment detail.
Can wall height determine geogrid length?
No. Reinforcement depends on the engineered system, soils, geometry, surcharge, water, connection, and stability checks.
Is drainage stone the same as structural backfill?
Not necessarily. The design may specify different gradations, zones, compaction, separation, and drainage functions.
Further reading
Authoritative sources
Use these primary and professional resources to check definitions, conventions, or requirements that may extend beyond this guide.