Wall Details
Select a wall type then fill in dimensions
⚠️ Walls over 1.5m require engineering and council consent in most NZ and Australian councils. This calculator is for walls under 1.5m only.
Wall Type
Timber Sleepers
H4 treated pine — most common DIY wall
Concrete Blocks
Besser block or segmental retaining blocks
Allan Block / Keystone
Interlocking segmental blocks, no mortar
Gabion Baskets
Wire cages filled with stone
Timber Sleeper Wall
H4 treated posts concreted in, horizontal sleepers bolted to posts
Wall Dimensions
m
Sleeper & Post Details
💡 Rule of thumb: posts go in the ground at least half the exposed wall height, plus 200mm. For a 900mm wall, post depth = 650mm min.
Drainage
💧 Drainage is essential for all retaining walls. Without it, hydrostatic pressure builds up behind the wall and causes failure.
AG Pipe (agricultural drain pipe)?
90mm perforated pipe at base of wall — highly recommended
Drainage Aggregate / Scalpings?
300mm wide free-draining gravel behind wall
Geotextile Fabric?
Separates drainage gravel from fill soil
Materials List
Your estimated quantities
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your dimensions, and calculate.
⚠️ Add 5–10% to all quantities for waste and breakage. Confirm quantities with your supplier before ordering.