Wood Retaining Walls

Retaining Walls - Wood

Retaining walls of wood (shown in cross section, right) are probably the least expensive and easiest to build. Because the wood contacts the soil directly, you'll need a rot-resistant type such as redwood, cypress or pressure-treated wood rated for ground contact (the longest lasting of the three).
Most walls have posts made from 4-by-4s, 4-by-6s or landscape timber. They are set in a deep, concrete-lined hole to provide support. A perforated pipe behind the wall provides drainage.

Step-by-Step

This wall is 34╜ inches above grade.

1. Dig and clear a level area.

2. Use stakes and mason's line to mark the locations of the wall and posts. The back of the wall should stand 12 inches from the bottom of the cut into the slope.

3. Dig postholes 42 inches deep on center and 3 feet 10 inches apart for the 4-by 4-inch posts. After aligning the posts add 1 inch of soil or gravel to each hole around the bottom of each post, and fill with concrete. The top of the concrete should sit 2 inches above grade and should be rounded to help water drain away from the post.

4. Nail horizontal 2-by-6s to the soil side of the posts. Space 2-by-6s 1/8 inch apart to allow for expansion.

5. Use a handsaw to trim the post tops flush with the top board, then center a 2-by 8-inch cap over the posts and wall boards.

6. Install drainage behind the wall.

By the Book

Building codes for retaining walls vary. Check local code requirements before you begin.

Tools

4-foot mason's level

combination square

mason's line

posthole digger

hand or circular saw

shovel

wheelbarrow

Tool and hardware-related resources on the Web