Preparation

Check with your community's building department before setting out to build a retaining wall. Many codes require a permit for any structure that holds back what amounts to thousands of pounds of earth, and most limit the height of an amateur-built retaining wall to 3 feet. If your slope needs a higher wall or requires extensive grading, call in a masonry or landscape contractor -- or terrace the slope with two or more lower retaining walls.

In addition to the usual carpentry and digging tools, you will want a baby sledge for hammering the 12-inch spikes. (If you have trouble driving these without bending them, consider predrilling holes.) Consider renting a chain saw: Cutting 6x6s with a circular saw requires several passes. In addition, a chain saw will let you trim the timbers in place. If your slope is extremely irregular or large areas need cutting, consider hiring an earthmover. Be sure to install the drainage gravel and pipe as indicated, or water pressure (a massive amount can build up) will eventually cause the wall to buckle.

• Landscaping timbers or salvaged railroad ties
• 3-inch perforated plastic drainpipe
• Gravel
• 12-inch spikes
• Filter fabric or tar paper
• Construction adhesive