How to Install a Stone Wall on a Hill
Building a rock wall on a hill supports a steep slope against erosion. Traditional stone retaining walls also enhance the aesthetic value of any landscape. Building a rock wall--to secure a loose hillside, build a trail or formalize the backyard garden--is one of the heaviest time investments in landscaping. The result is well worth the effort, however, due to the durability of stacked stone, which can remain functionally intact for decades to come.
Survey the slope to estimate how much stone you need. If at all possible, collect local stone loosened from eroding hillsides in the wheelbarrow. Granite, chert and quartzite stones are stronger than most country rock like sandstone or shale.
Stake the boundaries at the bottom of the hill slope, one foot out from the slope, and string the stakes. The line level is optional, but is recommended if the base of the slope is also reclined.
Remove vegetation, debris and large roots from the slope with the hard rake to create a clean, packed slope. If the soil is extremely loose, tamp with your boots.
Dig a trench at least six inches deep directly in front of the hill, starting at the lowest elevation of the slope.
Place the largest stones into the trench, starting with the lowest elevated side. Ideally, each stone should weigh at least 30 lbs. and be placed halfway below grade. Choose shorter stones for the higher elevated side of the hill so the tops of this first row of stones are level. Each stone, known as a face rock, should fit against the previously laid stone.
Insert smaller stones behind the first row of rocks like a jigsaw puzzle, so that the stones continue the level into the soil slope. Fill the gaps between these stones with even smaller stones. These stones, known as core rock, are the secret of the rock wall’s durability. Dig out soil with the hand trowel so the occasional longer stones can be inserted into the bank.
Build the wall in tiers, with a layer of face rocks, backed by core rock, for each tier that leans into the hillside. Test each layer of the rock cribbing by standing on the face rock, and correct for any movement with more core rocks.
Cap the wall at the top of the slope with the largest flat stones. For trails, use stones only a few inches above the grade of the proposed trail. For landscaping retaining walls, you may desire a higher profile for the rock wall.
Things You Will Need
- Heavy work gloves
- Two stakes
- String and line level
- Measuring tape
- Hand trowel
- Hard rake
- Drop the stone on the ground from four feet when choosing local stones to test its hardness.
- Don’t line up the gaps of the stones with previous levels, as this creates instability. This technique is called “breaking the joints.”
- Working with stone is hard on the body. Be prepared to lift over 50 lbs., and consider a back brace or a helper to make this physical work safer.