Retaining wall planning guide
Retaining wall materials and the right estimating workflow
Segmental blocks, poured concrete, reinforced concrete masonry, stone, timber, and gabions are different wall systems. Choose the system from the project design first. Then calculate the materials that belong to that system.
Estimate a segmental block wall01 / Compare the systems
Common retaining wall materials are not interchangeable
The visible material does not tell you the complete construction method. A segmental block wall may use a compacted leveling pad and drainage aggregate. A reinforced CMU wall may use mortar, filled cores, steel, and a concrete footing. A poured wall uses concrete and formwork. Each system needs its own quantity takeoff.
| Wall material or system | Main quantities | ConstructGauge workflow | Important boundary |
|---|---|---|---|
| Segmental concrete blocks | Wall units, caps, base aggregate, drainage aggregate, pallets | Retaining Wall Block Calculator | Product, embedment, drainage, and reinforcement must come from the project requirements. |
| Poured concrete | Wall concrete, opening deductions, allowance, separate footing concrete | Poured Concrete Wall Calculator and Concrete Footing Calculator | The calculators do not select wall thickness, footing size, concrete strength, or reinforcement. |
| Reinforced CMU | Concrete masonry units, mortar, grout or concrete fill | Concrete Block Calculator and Concrete Block Fill Calculator | Use the approved wall layout, filled cells, reinforcement, and manufacturer core data. |
| Natural stone or boulders | Stone quantity, base, drainage material, and site specific placement | No dedicated calculator | Irregular stone shape, mass, placement, and wall geometry need a project specific method. |
| Timber or sleepers | Posts, sleepers or timbers, connections, drainage, and excavation | No dedicated calculator | Member size, spacing, treatment, connections, and embedment are design decisions. |
| Gabion baskets | Baskets, lacing or connections, rock fill, foundation preparation | No dedicated calculator | Basket layout, rock grading, foundation, and stability need system and site information. |
The table identifies quantity workflows. It does not select a structurally suitable wall. The CMHA guide to segmental retaining walls identifies the leveling pad, wall units, retained soil, drainage fill, and soil reinforcement as separate system components.
02 / Match the calculator
Use the tool that matches the approved wall system
Start from the construction drawings, product system, or other approved project information. The calculator should turn known dimensions into quantities. It should not decide which wall to build.
Interlocking retaining wall blocks
Enter straight wall sections, exact block face dimensions, buried courses, caps, and the base and drainage dimensions specified for the project.
Open retaining wall block calculatorPoured concrete wall
Use known wall length, height, thickness, and opening dimensions to calculate gross concrete, deductions, net volume, and an optional order allowance.
Open poured concrete wall calculatorReinforced CMU wall
Count conventional masonry units first. If the design specifies filled cores, calculate that grout or concrete volume separately from the block order.
Open concrete block calculator03 / Understand the block choices
Segmental blocks and reinforced CMU require different takeoffs
Segmental retaining wall units are manufactured as part of a wall system. Their installed face dimensions determine the number of courses and units along the wall. Caps, leveling pad material, drainage aggregate, and possible soil reinforcement remain separate parts of the project.
Conventional CMUs are commonly laid with mortar. A reinforced CMU retaining wall may also require filled cells, steel, and a concrete footing according to its design. Use the Concrete Block Fill Calculator only after you know the installed block quantity, the manufacturer core volume, and the share of cores that the project requires to be filled.
Allan Block's material estimation worksheet demonstrates that unit count uses the exact product dimensions and that buried block, base, wall rock, caps, and pipe are separate quantities for its named systems. That worksheet is useful evidence for the estimating sequence, but its details are not universal defaults.
04 / Separate concrete quantities
Poured walls and their footings are separate concrete elements
For a poured concrete retaining wall, calculate the wall from its known length, height, and thickness. Subtract only openings that are shown in the project information. If the wall sits on a separate footing, calculate that footing independently with the Concrete Footing Calculator. Keeping the quantities separate prevents the shared boundary between the wall and footing from being counted as extra volume.
The wall and footing calculators estimate concrete volume from dimensions you provide. They do not determine stability, bearing capacity, wall thickness, footing geometry, reinforcement, concrete strength, drainage, or code compliance.
05 / Prepare the estimate
Information to collect before calculating materials
- Wall systemIdentify whether the project uses segmental blocks, CMU, poured concrete, stone, timber, gabions, or another designed system.
- Wall geometryRecord each wall run, exposed height, steps, curves, returns, openings, and repeated sections as applicable.
- Product dimensionsUse installed coverage and dimensions from the exact product documentation, not a broad catalogue name.
- Below grade workTake buried courses, footing dimensions, base dimensions, and excavation limits from the approved information.
- Drainage detailsRecord the drainage aggregate zone, pipe, outlets, filters, and other specified components without inventing defaults.
- Reinforcement detailsKeep geogrid, steel, filled cells, anchors, and connections tied to the actual design and system requirements.
A material comparison cannot establish whether a wall is stable. Soil, groundwater, slopes, nearby loads, wall height, available space, and local requirements can change the design. CMHA's segmental retaining wall design guidance treats external stability, internal stability, drainage, and site responsibilities as design matters. Use qualified local professionals and approved project information where required.
Next step
Estimating a segmental block wall?
Enter the wall runs and exact product dimensions, then add only the caps, base, drainage, pallet, and rate information that applies to your project.