Building a stone and mortar retaining wall in your garden is an easy way to incorporate dimension and architecture into the landscaping. Using mortar to adhere the stones will provide greater structural integrity to the wall and can be used to retain soil.
Choose the location to build a stone and mortar retaining wall and use landscape marking spray paint to outline the location and shape of the rock wall. Use an old garden hose to outline the shape of the wall first and once satisfied with the shape, spray paint alongside the hose.
Begin to prepare the base trench for the wall by removing the sod and soil materials with a square tipped spade along the marked area and stockpile the soil behind the wall for later use. The depth of the base trench should equal the depth of the stone being used to build the rock wall. Periodically check the base trench with a level to make sure the base is level. Use a measuring tape to make sure that the width of the base will accommodate the rocks being used for the first layer.
Mix the mortar according to the directions on the bag. The mortar should have a cake batter like consistency and will hold its shape.
Shovel the mixed mortar into the base trench to a depth of 4 cm (1.5 inches). Select rocks for the base layer of the rock wall and place them on top of the wet mortar. Gently rock the stones back and forth and gently rotate to give the stones good contact with the mortar. Again, place the level on top of the base layer and adjust any stones that are not level with smaller rock pieces or additional mortar.
Trowel enough mortar on top of the base to start the second layer of stones. Make sure to stagger the joints as each layer of stone is added. When placing the second stone next to the first stone, place a small amount of mortar in-between the stones along with the mortar placed on top of the lower layer. The joints should not line up from layer to layer. Use the level, additional mortar and small pieces of broken stone to level the layer. Use a hammer to break larger rocks to fit in smaller voids.
Continue adding courses of stone and mortar, ensuring that each course is level and that the rocks continue to overlap the butt-joints below, until the desired height is achieved. Backfill behind each rock layer with soil and tamp down with the shovel handle.
Use a hand trowel handle or a gloved hand to remove excess mortar and smooth it out to form a uniform appearance.
Use existing topographical features in the garden to enhance the dry-stacked rock wall. Incorporate the wall into a gentle slope or create a raised planting bed and use the rock wall to retain the elevated soil. Stick with odd numbered layers of rock. Building a stone and mortar retaining wall with even numbered rows will give the wall a patterned appearance.
Wear eye protection and a dust mask when mixing the mortar. Wear gloves when working with mortar to avoid skin irritation. Wear eye protection when breaking rocks with a hammer.