Prior to surface preparation, level and install a weep screed. You may also want to attach a temporary 2×4 starting strip. This will serve as a starting base for the first course of stones; which should be installed a minimum of 4” (10.16cm) above grade, when installed over earth, and 2” (5.08cm) above pavement.
Next, install the weather resistant barrier, using either a single or double layer technique. Boral Cultured Stone® recommends a double layer technique for best results. For the single layer technique, the weather resistant barrier is installed with 6” (15.24cm) lap joints, at vertical joints, and 2” (5.08cm) at horizontal joints. Inside an outside corners are overlapped a minimum of 16” (40.64cm). The weather resistant barrier is secured with galvanized staples. For the double layer technique, attach the half sheet, and install the full sheet completely over the half sheet, with a 6” (15.24cm) lap at the vertical joints. Continue up the wall, staggering sheets half lap.
Once the weather resistant barrier has been installed, the metal lath, or mesh, is attached. Here, galvanized 2.5 lb. expanded metal lath is used. When installing expanded metal lath, be sure that the grooved cups of the lath are turned upward. This is easy to determine by running a hand over the lath. The texture should feel rough when running your hand upwards. These cups prevent the mortar from sagging when applied to the vertical wall surface.
The lath is attached with galvanized nails or staples, that penetrate the studs at least 1-3/8” (6.03cm). Space 6” (15.24cm) on centre, vertically into framing. The lath must overlap 2” (5.08cm) at vertical joints, and 1” (2.54cm) at horizontal joints, and wrap a minimum of 16” (40.64cm) around corners, to a framing member.
If using a scratch coat, apply it to the metal lath by trowel, using enough force to key the mortar into the lath. The scratch coat should be about 1/2 to 3/4” (1.27 – 190.5cm) thick. When the mortar begins to firm up, cross scratch the surface using a stucco scratch coat rake. Curing time for the scratch coat will vary, depending on weather conditions.