Gardening or landscaping on a steep slope is a practice that most landscapers and agricultural experts discourage, due to the problems of soil erosion. Instead, most landscapers encourage terracing to create flat surfaces for gardens. One building material that you can use to construct terraces with is railroad ties. Railroad ties are constructed of heavy timber and do not shift easily under the pressure of dirt and moisture. Older railroad ties that a railroad has discarded are an inexpensive building material.
Contact your local utility companies to determine if there are any underground utility lines that you must work around when terracing. Knowing the location of utility lines will help prevent you from accidentally cutting or digging up your utility lines.
Drive a stake into the top of your slope and tie a plumb line to it. Hold a pole vertically at the bottom of the slope. Pull the plumb line taught and level and hold it against the pole. The length of the plumb line between the pole and the stake is the run. The height between the point where the line meets the pole and the ground is the rise.
Figure the number of terraces you will build and the size of each terrace by using the rise and run. For example, if you want to make a series of beds that are each 1 foot tall, then divide the number of rise feet by 1. So for a rise of 10 feet, you would construct 10 terraces that are 1 foot tall. Then divide this number by the run to determine the width of each terrace. If your total run width is 20, then each terrace would be 2 feet wide.
Mark the location for each terrace wall by driving stakes into the side of the slope at either end of the hill at the end points where the terrace walls will be. Tie a string between each stake for a reference while measuring.
Excavate the foundation for each terrace wall by digging into the hillside along the ground beneath the string. With a measuring stick, ensure that the foundation you are digging is level. Save the soil that you dig out to backfill behind the terrace walls.
Place a 1-inch layer of course sand into the foundation. Tamp the sand down with a tamping tool and lay a row of railroad ties over the sand. Drive railroad spikes through the holes at either end of the railroad ties and into the ground to hold the ties in place.
Stagger your second set of railroad ties over the first set so that the ends of the second row of ties do not meet in the same location as the ends of the first row of ties. Attach the second row of ties to the first row using railroad spikes. Continue to add rows of railroad ties until your terrace wall is the height that you have planned.
Tuck plastic landscaping fabric under the lower back corner of the railroad tie wall and bring the landscaping fabric up to the tip of the railroad tie wall. Railroad ties have been treated with creosote, a preservative. Creosote will damage plants if it leeches into the soil. By placing plastic over the back of the railroad tie wall, you will protect soil and plants from damage from this preservative.
Pour a 6-inch layer of sand into the hollow space between the railroad tie wall and the slope. Put a French drain pipe into a French drain pipe sleeve and lay the pipe over the sand layer. Cover the pipe with another 6 inches of sand. Backfill over the sand layer with the soil that you excavated to build the wall.
Cover the terrace with a layer of topsoil to ensure that the plants you place into the terrace will thrive. Repeat this process for each terrace wall.