The Footer Requirements for a Non-Structural Block Wall

Basic Footer Rules

• The normal requirements for non-structural footers is that you don’t need anything other than sand and gravel as a base. However, if you decide to pour a concrete footer on top of the sand and rock, such as with a mortared block retaining wall, the basic rule is that the concrete layer must be at least 4 inches thick and should be as wide as half the height of the wall. An example would be a 4-foot wall that has a 2-foot wide footer on the base.

Rock Layer

• One of the base layers for a retaining wall is the rock layer. This can be pebbles or gravel and must be anywhere from 6 to 8 inches thick. It must be compacted either with a hand tamper or a machine tamper, which you can rent from your local home improvement store. The gravel acts as a drainage layer to keep water from building up and freezing during the winter months. Water freezes and expands, buckling upwards and forcing the wall to buckle along with it if drainage isn’t allowed.

Sand Layer

• Settling is a natural process of any structure, because all buildings are set on top of soil of some kind. The layer of compacted sand that generally goes on top of the compacted gravel and under the first row of blocks acts as a compression layer. It gives the wall the support it needs to settle gradually, rather than all at once, which keeps the wall from shearing off and having two different heights. Without the layer of compacted sand, the wall potentially can knife down into the soil, cracking up the wall and sinking at different rates throughout the sections of the wall.

First Row

• Not all block walls require that you use a base layer of blocks or rock beneath the ground level. Some retaining walls must use a poured concrete footer. However, if you are building a stacked stone retaining wall you don’t need a concrete footer, but instead must sink the first row of blocks into the ground at least a few inches. The exact measurement depends on the manufacturer of the stone you are using, but most of the time you must include at least 4 inches for the first row of stone to be set below the ground level on top of the sand and gravel layers.