http://www.wikihow.com/Build-a-Dry-Stack-Retaining-Rock-Wall

1. Plan your project. Decide how wide and long you’d like your rock wall to be, and make sure that this is feasible with the location of your wall.
   

   Plan your project.

2. 2

   Select your stones from a stone supply yard. Give a representative your measurements, as that affects the quantity and size of stones you need. Dry stack walls can typically be made from three types of stones: round field stones, relatively flat stacking stones and uniformly cut dressed stones.^[2]

   

   Select your stones from a stone supply yard.

   • Each type will give your wall a different look and feel, so make sure you look at pictures to determine which would be the best fit for your house and landscape.
   • Note that flatter stones tend to be easier to work with than rounder ones, as they are more suited for stacking.
3. 3

   Lay out the wall area and direction. You may be cutting away a bank (shown below) or building the wall and back filling as you go, in order to create a terrace effect. Pull a string line the length of the wall (about 8 inches (20.5 cm) off the ground level) to define the front of the wall.

   
   • Freestanding dry rock walls can be stable if they are up to three feet in height^[3]
4. 4

   Dig a ditch the length of the wall that is about a foot wide and 8 to 12 inches (20.5 cm – 30.5 cm) below the ground level. This ditch will act as the wall’s footing and prevent the rocks from sliding forward due to pressure from the earth behind.

   
   • Try to cut the ditch into native soil rather than loose added soil, as the former provides a more stable foundation for the wall.
   • Level the foundation trench. Smooth over the ground beneath your wall with a shovel, and line it with crushed stone pieces called stone screenings, stone dust or fines.^[4] This material will also be useful for filling in gaps.
5. 5

   Stack the larger rocks in the ditch. Place the flat side facing forward, and slanted back about 8 degrees. The rock should just miss touching the string line, and be supported by dirt filled in behind it. Do this for the length of the wall, with each large rock touching the one next to it.

   
6. 6

   Fill dirt behind the large rocks and tap the earth firmly, while letting the 8 degree slant hold the rock in place by gravity.

   

   Fill dirt behind the large rocks and tap the earth firmly, while letting the 8 degree slant hold the rock in place by gravity.

   • Avoid large vertical gaps in your wall. Try to rearrange the stones so that those don’t appear.
7. 7

   Find complementary rocks to fill in the spaces in between the large rocks. These rocks may be smaller, but need to be a shape that fills the void between the large rocks. Lay the rock flat side out and support it with earth filled in behind it. These rocks also lay back by 8 degrees.

   
8. 8

   Continue placing the second layer of rocks, so that spaces between the first layer of large rocks are filled. Fill out the entire span of the trench. You can add water to the fill to make it settle.

   
9. 9

   Square off the top of the wall with smaller stones to give it a neat, straight and flat appearance.

   

Here’s How:

1. Check local codes before you begin digging (you may need a permit), although often you won’t be bothered if you keep the structure 3’ high or less. If your slope is too large for a 3’-high structure, you could terrace the slope by building retaining walls in 2 or more places, rather than trying to do the whole job with just one structure. Building terraces greater than 3’ in height is trickier. The mortar-less method discussed in this tutorial is not intended for such projects.
2. The great virtue of stone retaining walls that are mortar-less is that your “drainage system” comes built-in: water will usually seep through the cracks between the stones. When damage from water pressure does occur, it can be repaired easily enough. Another advantage in building terraces of this sort is that you do not have to sink a “footing” beneath the frost line, as you do when using concrete or stone and mortar.
3. Select stones that have at least two sides that are flat (what will become the “top” and the “bottom” once in place in the structure). The heavier the stones, the more stability you’ll have -– but also the harder the work (but it will be worth it).
4. Plot out where the retaining wall will sit at the bottom of the slope, using stakes and string for a straight terrace, a garden hose for a curved one. The advantage of a straight terrace is that you can attach a line level to the string to make sure the courses of your retaining wall are level.
5. Dig a trench about 8”-10” deep, so that the first course of stone is fully or mostly submerged. This will help your retaining wall withstand the pressure exerted on it by the slope it is holding back.
6. To calculate the necessary width of the trench, just remember the base of the structure should be half the wall’s height. Angle the trench so that it inclines back slightly into the slope (2” for every 1’ of terrace height) – this will provide greater stability.
7. When you’ve almost penetrated down to the required depth, use a skimming motion to remove the remaining soil, so that you don’t end up with a base of loose soil. Keeping the base as solid as possible will reduce the chances of shifting as the retaining wall settles.
8. Terraces of natural stone are laid in “courses,” i.e., a horizontal row at a time. The first course of stones will consist of your largest, widest, longest, flattest stones (but save some for the final course, the “capstones”). They have to be the most stable stones. Take the time to fit them as closely together as possible. Building terraces with natural stone is like fitting the pieces of a puzzle together -– only it’s a puzzle that can turn out many different ways.
9. In terms of the height of the first course of stones and the following courses, you have two choices. If you’re aiming for a look of uniform rows, choose stones of the same height when laying a particular course. The other option is a more random look, in which you play each course by ear, using filler stones wherever necessary to make up for a difference in heights. Sometimes you are forced into the latter option, because the stones you have to work with simply aren’t uniform enough.
10. Check to ensure that the stones run level left to right. But because you’ve built a slight backwards slope into the trench’s base, your stones will slope down slightly front to back. After completing this first course (the foundation, if you will) backfill with some of your excavated soil and any stones too small to use for building the retaining wall, and tamp it down.
11. In laying the next course of stones and those that follow, avoid lining up the joints over the joints of the course underneath. Again, backfill and tamp down after completing the course. Also tuck soil in between any gaps in the terrace, to serve as “chinking.” When you’re finished building your retaining wall, you can root plants into this chinking and bring life to the structure. Cascading plants, such as thyme and the annual, lobelia are very attractive in stone retaining walls.
12. As you place each stone, check that there’s as little wobble as possible. To counteract any wobbling, you may have to use small, flat rocks as “shims.” Use a mason’s hammer to knick off stone fragments so as to achieve a better fit where possible.
13. Continue in the same manner with the third course and succeeding courses. By the time your terrace is half its planned height, you should start incorporating what are known as “deadmen.” In the case of stone retaining walls, the term refers to long stones laid perpendicularly across the wall, rather than parallel to all the other stones. The idea behind deadmen stones is to tie the structure into the slope in back of it.
14. A hole is first dug into the slope to incorporate a deadman. Then one end of the deadman is set on the terrace (as part of whatever course you happen to be laying), and the other end placed into the hole you’ve just created in the slope. The longer the stones you can find to serve as your deadmen, the better. The Colorado State Extension states that “A good rule of thumb is to provide at least one deadman per 16 square feet of exposed wall face.”
15. When you’ve almost reached the desired height for your terrace, it’s time to place the capstones on top. “Capstones” are similar to the stones used in your first course, in the sense that they should be flat and have significant mass. They serve both to help hold the stones under them in place and to provide a finished look to the structure (thus the importance of their being flat).

Tips:

1. After you’ve built your stone retaining wall, you’ll want to plant something in the soil being retained, to further anchor it. An excellent low-maintenance choice for sunny areas is “Blue Rug” juniper shrub, a low-growing evergreen.

What You Need

• line level and string / garden hose
• shovel
• mason’s hammer
• stakes
• carpenter’s level

Summary: Building a rock retaining wall can add a lot of value to your property. But a rock retaining wall is a major project. Retaining wall rocks are heavy and the rock retaining wall design must be able to withstand a tremendous amount of pressure.

After one day of moving rock around, you’ll possibly be muttering to yourself that this was a very ambitious project.

Retaining wall rocks are plentiful in many parts of the USA, but in some areas they are as scarce as rainfall in the Atacama Desert. Before you go too much farther into this project, make sure you calculate the correct quantity of rock you’ll need. You can do this by estimating the square footage of exposed wall you intend to have. Once you have a quantity, calculate the cost of the rock. If you have to buy it, you may be in for a surprise as to how much it costs. The farther you are away from the source of the stone, the more it will cost. Freight costs to transport the rock can be very high.

These rock retaining walls will last for generations because they were installed correctly. PHOTO CREDIT: B&D Rockeries

The rock you use for your retaining wall must be durable if you want it to last generations. Not all rock is the same. Some like granite and limestone can easily last for hundreds or thousands of years. Cold weather is rock’s enemy as water that seeps into tiny cracks can freeze and blast apart the rock over time. I can see that happen with the rock in my yard here in New Hampshire. It’s a very durable granite, but this spring I saw some small quartz crystals that were broken away from the stone during the winter.

Rock retaining wall construction can be very challenging. The rock themselves are very dense. It’s not unusual for a cubic foot of rock to weigh between 150 – 200 pounds. Large boulders will either require you to have a piece of mechanical equipment or you have to master using gravity to help you lift the stones in place.

Gravity can help you lift stones as crazy as that sounds. A retired carpenter, W. T. Wallington of Lapeer, Michigan, discovered just a few years ago how to lift and move huge 10-ton blocks of stone and concrete by simply taking advantage of the center of gravity of the object. You can see how he did this at his website: www.theforgottentechnology.com

Retaining-wall science can be complicated, especially as the height of the wall increases. Walls over 3 or 4-feet tall can begin to have significant loads against them from the soil that you’re trying to hold back. If you’re planning a tall retaining wall, I highly recommend that you have it engineered. You don’t want the wall falling down injuring or killing someone or damaging your property.

Your rock retaining wall design will require you to decide between a dry stacked wall versus one made where you mortar the stones together. I’m a fan of dry-stacked walls because they can be long lasting, easier to construct and resist the freeze-thaw cycles that create frost heave and soil expansion that tips over retaining walls. Come to New England to see a dry-stacked moss rock retaining wall and you’ll realize the wall has been standing for generations to have accumulated the natural moss patina.

If you decide to set your rock in mortar, I suggest you take the time and build a small test wall until you master the technique. Make the mortar very weak using a minimum amount of hydrated lime and Portland cement. This will allow you to take apart the wall and salvage the rock. I would mix ten parts sand to one part each of lime and cement for this lean mortar mix.

Most rock, because it’s so dense, doesn’t have the suction of brick and concrete block, so make the mortar mix fairly stiff. Without suction, the mortar mix stays plastic for some time. If the mortar doesn’t get stiff from water loss fairly quickly, you can’t stack more rock on the wall as the mortar moves in the lower rows or courses.

Soil can be very heavy, especially if it’s wet. A cubic foot of soil often weighs nearly one-hundred pounds. Keep this in mind as you start to build a rock retaining wall. Your wall needs to resist the push of this soil against the wall. If the ground above your wall is sloped, you have tremendous pressure pushing against the wall as the soil succumbs to the pull of gravity.

When dry stacking a rock wall, you need to be concerned with the friction between the individual pieces of rock. This friction needs to be greater than the push of the soil behind the wall, otherwise the soil will push a course of stone from a lower one.

If you intend to create a flat area above a retaining wall that will act as a parking area for cars or trucks, you need to account for this extra surcharge load. Some of the weight of the vehicles will push against the wall, especially if the tires are close to the edge of the top of the wall.