Building a Timber Retaining Wall
A retaining wall made with timber posts can add style and extra seating to your yard .
Determine the length, height and location of the retaining wall. Take the measurements to a stone supply yard and select the material for the project. This project uses granite slabs for the steps and field stone for the wall. Have the yard deliver the material to the project site.
Establish the face of the retaining wall by hammering a piece of rebar into the ground at both ends. Tie a piece of nylon string tightly between the two pieces of rebar, using a line level to make sure the line is level.
An average step is approximately 6 inches in height. Use a tape measure to determine the distance from the top point of the completed wall down to the ground. In this project, that distance is 18 inches, meaning that there will be three slab steps.
Mark and dig the footing for the first step to a depth of 6 inches. Prepare premixed concrete according to manufacturer’s directions. Pour concrete into excavated hole and smooth with the back of a metal rake. Continue pouring and smoothing until the concrete reaches a height that is just below grade.
Place the first granite step onto the footer so that the front is flush with the wall face. The top of the step should pitch forward slightly so that water will run off. Check for level from side to side (Image 1).
Never attempt to dead lift heavy stone. Instead, flip or walk the granite into place (Image 2). When flipping the granite, place a small rock underneath one end so there is space from which to lift. Walk pieces of stone into position by rocking them from corner to corner.
Dig the footer for the second step directly behind the first step. Pour concrete into the footer hole and smooth with an iron rake. Set the front of the second step on the back edge of the first step (Image 1). Repeat this process until all the steps are set.
To cut granite, first mark a straight and square line across the width of the stone. With a hammer gun, drill 3-inch-deep holes every 4 inches along the cutting line. Insert two feathers and a wedge into each hole. Pound the wedges with a stone hammer until the stone splits (Image 2).
Excavate to a depth of 6 inches along the entire base of the stone retaining wall, using the string marker as a guide. For dry-stack walls, the base should be as wide as the wall is tall. For this 18-inch high wall, the footing should be at least 18 inches wide. Use a hand or power tamper to level the base. Add 3 inches of gravel and compact with hand or power tamper.
Begin building the wall by setting corner stones (those with a 90-degree corner) at either end of the wall and on both sides of the granite steps. Start setting face stones (those with a flat face) between the corner stones. Every three or four feet, lay a tie-back stone (flat, long and heavy) to provide additional stability. Continue laying corner and face stones to build up the wall until desired height is almost reached. Regularly check that the wall is plumb. For the final course use cap stones (smooth top, flat face) (Image 1).
For the strongest possible wall, every stone set should be secure before another is placed on top of it. And always stagger the joints between courses.
For the final course use cap stones, stones with a smooth top and flat face. It is aesthetically important that these final stones fit together nicely to create a smooth, flat surface. For a more secure top, some experts set the cap stones into a bed of premixed mortar.
As you build the wall, toss all unwanted stone scraps behind the wall. When the wall is complete, backfill behind it with gravel up to the level of the cap stones. Top this gravel with colored stone or mulch to suit the desired look of the landscape.