The Styles of Retaining Walls

Setback

• The proper setback for a retaining wall helps reinforce it and adds variety to the design with different levels. Setback is the amount each layer of a wall steps back or cuts into the slope. The setback ranges from the lowest level, zero, up to 1 1/4 inches per row.

Drainage

• Poor or improper water drainage weakens a retaining wall. To help preserve a wall's stability, place a drain pipe behind it the length of the wall. The pipe collects water through small holes and then drains it away through the ends. When using concrete blocks, drill 1- to 2-inch weep holes every 24 to 36 inches to let the water drain.

Concrete Blocks

• Built for strength and durability, a concrete block retaining wall is a simple and affordable solution. The blocks stack on top of each other and are held together with gravity, or clips for added strength. Place a base of 2 to 3 inches of gravel, then lay the first layer of blocks. The gravel allows the concrete blocks some flexibility to adjust to natural ground movement. A garden or terrace wall, less than 30 inches tall, needs smaller concrete blocks, about 12 inches long and 4 inches high. For a retaining wall taller than 30 inches, use full-size blocks that measure 18 inches long and 6 inches thick.

Natural Stone

• A retaining wall of natural stone adds a rustic appearance to landscaping. Stone retaining walls look best 3-feet high or less. The most common materials for a stone retaining wall are rubble, cut stone and boulder. A rubble wall is made from smaller stones of random shapes fitted tightly together. Flat pieces of cut quarry stone, 8 to 12 inches wide, stack in rows, mixing different colors. A boulder retaining wall consists of stones up to 18 inches high that can weigh up to 80 lbs. each. Gravity holds the stones in place, so mortar is not needed, but put soil in the gaps between the stones. The disadvantages of stone retaining walls are the higher cost and more construction time.

Wood or Timber

• Cheaper and easy to construct, wood retaining walls use standard lumber sizes, such as 2 x 4, 2 x 6 and 2 x 8. Timber sizes are larger, 4 x 6 and 6 x 6. The wood can remain in its natural color, stained or painted to match the surrounding area. The lumber fastens together with spikes or long screws and can include different angles and steps. Choose treated lumber to resist termites, and seal the ends with a wood preservative to prevent rotting. Wood retaining walls require additional bracing to the face and sides of the wall with cross supports.