Natural stone provides a rustic and classic appearance for home exteriors, fireplaces and other applications, but it also has its drawbacks. Natural stones can be expensive to purchase and heavy to carry, making installation a sometimes difficult process. Some installers and homeowners turn to stone veneer, which is a lighter, thinner mix of cement and stone aggregate that looks like natural stone. Veneer can easily be installed over all masonry surfaces, including concrete blocks.
Clean the entire concrete surface with a low-pressure power washer or by scrubbing with a mixture of warm water and dish detergent. If there is paint on the concrete surface, use a paint stripper to remove it. The adhesive used for stone veneer does not bond with dirty or painted surfaces.
Mix two parts sand to one part Portland cement to the consistency of creamy peanut butter. The actual amount of sand and cement needed varies depending on the size of your installation area. Stir the mixture with an electric mixer for at least five minutes to ensure the ingredients are completely combined.
Moisten the concrete wall lightly, so that it is damp but not soaked. The water on the wall slows the drying of the mortar, allowing it to form a more solid bond over a longer period of time.
Trowel a ½-inch layer of mortar onto the concrete surface within 4 to 5 feet of your starting area. Do not apply mortar to larger areas, as it can dry on the surface too quickly for proper bonding with the stones.
Dampen the back of your first stone veneer piece to remove dust or dirt. Spread a thin layer of mortar across the back with your trowel and push the piece into place. Turn the piece slightly to ensure proper coverage; you will probably see some mortar leak out from behind the stone's edges.
Continue adding stone veneer pieces. Remove any excess mortar from joints between the pieces with the trowel or with a joint tool before the mortar can dry. Excess mortar can create an uneven finish. Continue until all pieces are installed.
Fill a grout bag with mortar. Use the bag to carefully fill in all joints, ensuring even coverage throughout all joints. Use a joint tool to shape the mortar if desired. Wipe away all excess mortar from the face of the stones with a brush or damp rag. Do not let mortar harden on the faces.