Resources for Retaining Walls

Retaining walls are used for decorative, drainage and erosion control purposes. In some cases, they're built of water-permeable material to improve drainage, for example at the edge of a riverbank. But in places where heavy rainfall or other water flow may wash the backfill out from behind the retaining wall, water-permeable barriers and drain tiles may be put in place to make water flow around the wall instead of through it.

Most vocabulary dealing with retaining walls is fairly common sense if you've any familiarity with general building terms, but there are some specific key terms you should understand, especially in relation to different building materials and types of walls.

Gabions

Gabions are wire mesh containers that are filled full of rocks at the building site, then set in place to form a retaining wall with superior flexibility and drainage.

Batter

The batter, or setback, refers to how much each layer of retaining wall blocks, mortared or not, is set back from the layer below it. This backward, inward slope to the wall tends to strengthen it.

Dry stacked

Dry stacked retaining walls are built of stones, usually flat, which hold together purely because of friction. No mortar is used. Because there is no mortar used, dry stacked walls have a little bit of flexibility, which means a concrete foundation is not necessary to protect them from the freeze thaw cycle.

Mortarless

Mortarless retaining walls differ from dry stacked walls in that they are made of bricks with a protruding lip on the bottom rear side so that, when stacked and filled from behind, the pressure of the fill soil presses the bricks forward and the protruding lip locks them in place, strengthening the wall.

Foundation trench

The foundation trench, which allows the first course of blocks or other building material for your retaining wall to be set into the ground and completely level, is critical for building a strong, stable retaining wall.

Poured concrete

Poured concrete is made out of the same material as concrete blocks: Portland cement, gravel and sand. The major difference is that while blocks can be stacked, removed and even replaced if necessary, poured concrete is one solid piece that's literally poured or spread into place and then left to dry.