Retaining Walls Any wall up to 30 inches in height is considered a garden wall and can be built without submitting structural engineering plans to the City. Any wall over this 30 inch threshold must be engineered and inspected.
The construction of retaining walls starts underground with a footing. The toe of the footing points to the daylight side and the heel to the up-hill, or retained side. Most footings are engineered with the toe larger than the heal to prevent over-turning. However, if the site conditions necessitate a very large amount of excavation and subsequent filling and compaction to accomplish this, the engineer may be able to accommodate the converse.
Conversely the foundation of some retaining walls is a row of caissons, connected together with a grade beam (concrete "beam" at grade).
It is the rebar inside the CMU blocks that gives the retaining wall its strength. Retaining walls are built in increments of not to exceed four vertical feet, to ensure that the grout completely fills the voids inside the blocks.