How to Build a Hillside Rock Wall
- 1). Excavate a trench for the base material. The trench should be slightly wider than the rock base and deep enough to accommodate 5 to 7 inches of base material plus an inch of wall material for every 8 inches of above-ground wall height.
- 2). Prepare the foundation for the wall. Place 4 to 6 inches of coarse gravel in the trench and compact it with the tamp, checking for level regularly and moving or adding gravel as needed. Spread an inch of bedding sand on top of the gravel layer and again check for level, making any necessary adjustments.
- 3). Place the first layer of rocks in the trench. Use the heaviest, widest rocks for this base layer. Make the first course of rocks as level as possible. Add extra sand under rocks wherever necessary to make the first course more even.
- 4). Set the second course of rocks on top of the first course. Try to stagger the rocks so that vertical joints do not align between courses. If the wall is serving to retain earth, set each layer back about 3/4-inch from the face of the layer below it so the wall will lean back slightly and have added stability. If there are not enough rocks large enough to span the width of the wall, make the wall two rocks thick but place tie stones that span the width of the wall atop doubled rocks regularly throughout the placement of subsequent levels. Fill in spaces between larger rocks with rubble and use shims to prop up larger rocks as needed to make them level or keep them from wobbling.
- 5). Backfill behind each course of rock as the wall is built. Fill the area immediately behind the wall with coarse gravel to encourage draining and the remainder of the space behind the wall with regular soil from the site.
- 6). Continue placing layers of rock that are fairly level, firmly set, filled in with rubble and backfilled with gravel until the desired wall height is reached.
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