Metal lath provides a mounting surface on concrete walls for materials that are too heavy to mount otherwise, especially stucco or stone veneers. Because the materials you plan to attach to the lath are so heavy, you need to fasten the lath in a way that attaches it securely without movement separate from the wall's surface. You can use concrete nails to attach the lath firmly to the concrete without damaging the concrete in the process.
Prepare the wall before mounting the lath by repairing any moisture related problems. Then wash the surface with a pH-neutral cleaner and then rinse it with clean water. Allow the wall to air dry for 24 hours, or pat it dry with a cloth and wait two hours for the drying process to complete before continuing.
Roughen up any paint on the wall surface by sanding the wall in a series of small circles using medium-grit sandpaper. Painted surfaces can interfere with the adherence of adhesives, plaster or mortar placed against the mesh after mounting. The sandpaper removes the finish that causes the interference and creates a texture that makes it easier for the materials to adhere to the painted surface. Wipe away any residue left from sanding with a clean dry cloth.
Measure the concrete wall with a tape measure, and then cut the lath to fit the surface area using a pair of tin snips. Wear leather gloves when handling the lath as it is extremely sharp when cut. Many surfaces require more than one mesh sheet. If you are using multiple pieces of mesh to cover the surface, then allow for overlapping edges when measuring and cutting the sheets for placement. Add space for a 6-inch overlap where two pieces meet with a vertical seam, and a 2-inch overlap where they meet with a horizontal seam, when cutting the lath.
Hold the lath against the wall with the diamonds created from expanding the mesh pointed upward. Secure it in place using 7/8-inch concrete nails with a washer over the nail shaft to hold down the mesh strands. Drive the nails through the mesh into the concrete wall using a hammer. Space the nails one nail every 6 inches with staggered rows for best results. Drive the nails through the overlapping edges of the lath sheets to prevent the edges from curling upward when covering the lath.
Bend the mesh around wall corners if you need to continue the surface onto adjacent walls. Make sure to extend the sheet at least 6 inches after rounding the corner, using the normal overlapping spacing with the next sheet.