How to Build a Dry-Stack Stone Retaining Wall
A dry-stack stone retaining wall not only holds back the earth, it adds beauty to a landscape.
To lay out the curve of the wall and to define the area that needs to be dug out for the trench, or foundation, we're going to use a household extension cord as our marker. Some other things that work just fine are a garden hose or even a length of rope. If the wall were to be straight, we could have used string and stakes, but the hose works great for laying out a curved wall.
After laying out the marker extension cord, it's time to dig out the trench. Skim off any grass, and set the dirt of the trench aside for later use. If your wall is going to be long, a backhoe or tiller rental can be a back-saving investment, but since this wall isn't going to be all that long, the long-handled shovels and some good old-fashioned sweat get the job done.
A good rule of thumb when digging the trench is to dig it about 6" deep and fill it with about 3"-4" of fill gravel. Then tamp it down to about 2".
To determine the width of the trench, add 6" to the width of the stones you're using. This enables you to place your stones with 2" left up front and 4" left behind.
The trench is the solid foundation on which to build a wall, so make sure that the fill gravel is put into the trench and really tamped down until it is compacted and level.
Note: To tamp down as solidly as is necessary, you will need to use a tamper. There are two types, a hand tamper and a power tamper. Use the one with which you are most comfortable.
Place the stones so that they touch side by side; they should be fairly snug as they're laid down. Level each stone as it's put in. Use a torpedo level to check the side-to-side level of the stones as well as the front to back level. Use the gravel to help level the stones. Finish the first course of stones.
It may be necessary to cut some of the stones as the wall comes together: that's where the wet saw comes into play. The wet saw is the perfect tool to rent when building a retaining wall. With its diamond blade, it cuts the stones pretty easily. Simply mark your stone at the desired size and cut. But if you're going to be cutting only a few stones, that can be done with a hammer and mason's chisel as well.
Now that the first row of stones is in, get ready to install the drainage in the wall. The first step is to add gravel to the back of the first run of stones (Image 1). Put the gravel into the trench and tamp it down lightly. The gravel acts as an aid in drainage.
PVC drainpipe is laid on top of the gravel with the drain holes facing down to evenly distribute the draining water (Image 2). It runs the length of the wall and out into the yard. The ends will be coupled with PVC pipe outlets for the drainage. This serves the purpose of moving water away from the wall, minimizing any damage that it might cause.
Once the drainpipe is in place, cover it with more gravel. Then lay down a layer of GEO textile fabric (Image 3) to line the back of the wall and trench. This fabric serves as an erosion barrier as well as keeping fine particles from seeping through the stones of the wall.
The fabric should line the back of the wall as you build up. The best way to do this is to fold the fabric onto the dirt as the next course of stones is added.
Looking at the back side of the stones, you'll see a lip. This lip is here so you know exactly how far the stones will need to slide forward onto the row beneath. Each additional row of stones should be staggered so that the joint of two stones is covered by the center of the stone above. Remember to push the stone forward until the lip catches. Backfill the wall with soil as you add courses.
Distribute an even layer of mortar to the prepared base for the wall. When you apply the first run of stones, tap them down to get them set into the mortar. Use a level to make sure this first run is level, front to back and side to side.
Some walls require mortar. We're using a quick-set mortar with this wall and have followed the manufacturer's instructions for its preparation.
The key to building a wall using mortar is when you apply the mortar it needs to go evenly onto the run of stones that are set. After spreading the mortar, but before laying the next stone, use the trowel edge to cut the mortar even with wall face. This prevents mortar from running down the face of the wall.
Butter the ends of the stone. Try matching the width of mortar that was laid down on top of the previous row to maintain an even and clean feel. Tap the stones with the butt end of the trowel into a tight fit on the wall. Throughout you should be checking for level, both vertically and horizontally.
When the wall is done and the mortar is set but not hard, tool the mortar for a clean look. Capstones can be added once the wall is done and the mortar is dry.
Using the adhesive in a caulk gun, apply two good size beads to the top course of stones. Place the capstones onto the adhesive, and then pick them back up and replace again. This allows the adhesive to spread evenly on the stones. Remember to stagger the stones so that the center of the capstones aligns with the joint of the stones beneath. Now the wall is done ... and should serve its function quite well.
The finishing touches to this project are to add some landscaping. The choices of plants and other vegetation are varied, and really come down to personal choice. The key factors are the amount of light the area gets along with the climate.