Estimate the amount of materials you will need. Measure the wall and multiple the length of the wall by the height. This gives you’re the gross square footage. Subtract any square footage for windows or doors.
Prepare your wall. Preparation instructions will vary in accordance with the type of wall to which you are applying the stone. If your wall is made of plywood, wallboard, concrete board, paneling or polystyrene insulation board you will need to cover it with a breathable, weather-resistant barrier; install mesh or lath and install the barriers securely around all inside and outside corners. If you are applying stone over masonry, stucco or concrete, make sure that the surface is free of oil by etching the surface with muriatic acid then rinse clean. If the wall is dirty or painted, sandblast the surface and wash it clean.
Mix the mortar according to package instructions. If you are applying natural stone, you will need three batches for a scratch coat, setting bed and grout. If you are using stone veneer, you can use a pre-mixed type N mortar and you will need one batch for the wall and the back of the stones, plus more for grouting.
Work from the top of your wall downward to avoid dripping mortar on stone below. Apply mortar to your wall surface using a trowel. Also apply mortar (approximately 3/8-inch thick) to the back of your stone. Apply with a back-and-forth motion to the mortar on the wall.
Begin with the corner pieces (if there are any) and then move to the flat pieces. Keep the joints consistent and place stones close together to create uniform joints between the stones. Press the stone firmly into the mortar bed until you see mortar oozing around the edges of the stone; this will ensure that the stone and mortar have formed a good bond. Trim extra stones and use to fill in any gaps. A hatchet or wide-mouth nippers will work for veneer, a power saw equipped with a masonry blade will be needed for natural stone.
Apply grout with a grout bag, avoiding getting mortar on the stone’s face. Fill the gaps slightly higher than your desired final depth since the grout tightens as it dries and will seal the area around the stone. Allow the grout to dry to a firm consistency and then strike it with a striking stick. Scrape along the joints, giving your grout an even and clean appearance. Finish by sweeping your new stone wall with a medium bristled brush to remove any dust.