Why bury a whole course?

It stops the base sliding forward under load. A buried base course is standard practice and is why a 1.2 metre wall is built 1.35 metres tall.

Construction & Homestructural

Retaining Wall Calculator

Block count for a segmental retaining wall, counting the buried base course that people forget. Drainage gravel behind the wall matters more than the blocks.

Also called: retaining wall blocks, segmental wall calculator.

Blocks

189

189 blocks for 10m at 1.35m total height, which is 7 courses. Base gravel comes to about 4.05 m³.

Courses

Blocks per course

Total height including the buried course (m)

1.35

Base and backfill gravel (m³)

4.05

Face area (m²)

13.5

How this is calculated

Method and background

How this is calculated

Blocks per course times courses, where the course count includes the buried base. The base course should be fully buried for stability, so the wall is taller than it looks. Free-draining gravel behind the wall is not optional: hydrostatic pressure from trapped water is what pushes retaining walls over.

blocks = blocks per course * number of courses, counting the buried base course

L: Wall length (metres)
h: Exposed height (metres)
d: Buried depth (metres)

Worked examples

Each of these is asserted on every build. If a change to the engine ever moved one of these answers, the build would fail before the page could print it.

a ten metre wall at 1.2m exposed

Wall length (m): 10
Exposed height (m): 1.2
Block length (mm): 400
Block height (mm): 200
Buried base course depth (mm): 150
Wastage: 8%

Blocks189

The buried course makes it seven courses rather than six

Open this example

no buried course loses one

Wall length (m): 10
Exposed height (m): 1.2
Block length (mm): 400
Block height (mm): 200
Buried base course depth (mm): 0
Wastage: 8%

Blocks162

boundary

Open this example

Method and limits

What it assumes

A straight wall with a level base and one buried course.

What it deliberately does not model

Walls above about 1.2 metres usually need engineering and geogrid reinforcement.
Caps, adhesive and drainage pipe are separate items.

Formula version 1.0.0 · definition 1.0.0 · India · Report a problem with this calculator

Frequently asked questions

Why bury a whole course?: It stops the base sliding forward under load. A buried base course is standard practice and is why a 1.2 metre wall is built 1.35 metres tall.