- 1). Thoroughly clean the concrete block to remove all surface dirt, dust and contaminants. If the surface is simple concrete, scrub off surface dirt and dust with a scrub brush and hose. For treated concrete, such as that which has been painted or oiled, sandblast or etch the surface to remove the treatment. This is often best left to a professional.
- 2). Spread out the pieces of cultured stone around the installation area so you can see all the stone. As you work, you will be able to choose the sizes, hues and shapes to create a truly varied and natural-looking surface.
- 3). Dampen the concrete block surface so the surface looks damp but does not have excess water. You should not get water on your hand if you brush your fingers along the surface, but the concrete should look damp. This means that the concrete itself is slightly moist but that the water will not interfere with the mortar.
- 4). Run a 2-by-4-inch board along the bottom of the concrete block. Attach the wood to the concrete using concrete screws. Use a level to ensure that this strip sits completely flat. This will give you a line to follow to ensure the installation is flat.
- 5). Mix mortar and water per product instructions by pouring both into a large bucket and stirring with a drill mixer. Your goal is to mix the mortar to a consistency similar to that of pancake batter so it will spread easily but will not dry too quickly.
- 6). Spread a ½- to-¾-inch thick layer of mortar over the dampened concrete surface with a notched mason's trowel. Start from the top and work your way down in 5- to 10-square foot areas so the mortar does not dry as you work. Starting from the top helps you avoid dripping mortar onto previously installed stones.
- 7). Firmly press the pieces of cultured stone into the mortar, setting the pieces as close together as possible. You should see some mortar squeeze out around the edges of the stone, indicating that it is holding firmly in place. In general, the gap between pieces should be no larger than ½ inch. Try to keep the joints even for a flowing appearance.
- 8). Shape the stones as necessary with stone nippers. Always wear a dust mask and safety glasses to avoid injury from shrapnel. Line cut edges with a thin layer of mortar to smooth out rough edges. Continue until all stones are attached to the concrete block.
- 9). Inspect the surface. If necessary, fill in gaps or spaces between the stones with mortar squeezed from a grout bag. This will be necessary only if your installation appears broken up or uneven.
- 10
Allow the mortar to dry to a thumbprint dryness, meaning that when you press your thumb into the mortar it will shift but will not show your full thumbprint. This timing will vary depending on temperature and humidity but generally takes at least a few hours. - 11
Point the semi-dry mortar with a jointing tool. Seal the mortar tightly to the edges of the stones and scrape out any excess mortar or high points to create a finished-looking job. Allow the mortar to dry fully for at least 24 hours before continuing. - 12
Run a whisk broom or stiff-bristle brush over the surface of any stone that has mortar over it. The ill-placed mortar should crumble off the face of the stone. Do not use any water or else the mortar will sink in and stain the stone surface. Remove the leveling strip when installation is complete.
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