Crib block retaining walls

How a crib wall works

A crib wall is a cellular gravity wall. Precast headers run into the bank and precast stretchers run along the face; the cells between them are filled with crushed rock. The assembled mass, not any single component, resists the earth pressure behind it. Because the units are dry-stacked and the fill is granular, the wall can flex slightly with the ground and drains itself through the face.

The system was developed for ground that moves. That is why it has been the workhorse of civil retaining in Sydney for decades: it copes with reactive clays, settlement and vibration in a way a rigid wall does not.

Design, supply and construction

We take a crib wall from the geotechnical report through to the certified structure. Wall geometry, batter, base preparation, drainage and any geogrid reinforcement are designed to the site, then the units are supplied and placed by our own crews and plant. On larger walls a machine with a block grab sets the courses; on tight sites the units are placed by hand.

Every wall is built to the engineer's drawings and inspected as it rises, so the completed structure can be certified without rework.

Finish and planting

A crib face reads as a pattern of precast units with open pockets between them. Left open it drains freely and greens over naturally; planted deliberately it becomes a living wall. For projects that want a solid finish, a closed-face unit is available. Either way the wall is finished on the day it is built, with no rendering, painting or capping to follow.