How to Install Precast Stone

Cut strips of 3.4 lb. expanded metal lath the length of the house’s wall with tin snips. Attach the lath to the house with 1 1/2- to 2-inch-long nails spaced 6 inches apart. The lath has tiny cups that should be face-up. Overlap lath joints 6 inches on vertical seams and 2 inches on horizontal ones. Keep the lath pulled tight as you install it.

Mix together 1 part Portland cement, 1 part lime and 4-1/2 parts sand. Add enough water to create a stiff mortar. If you prefer, use premixed mortar and add water, according to the package directions.

Apply a scratch coat of the mortar mixture with a trowel. Work the mortar into the lath cups. Create a smooth surface that covers all of the lath. Allow the mortar to dry until you can leave a thumbprint in it. Once it reaches that point, scratch horizontal marks into the mortar with a hand rake. Allow the scratch coat 48 hours to dry.

Mix another batch of mortar. Spread the mortar 1/2- to 3/4-inch thick on the entire backside of a section of faux stone. Starting at a top corner of the wall, press the section of precast stone firmly into the scratch coat. Twist or wiggle it slightly to seat the mortar into the scratch coat. A small amount of mortar should ooze out from behind the stone section.

Hold the next section of stone against the first one. Note any stones you need to cut away to fit the sections together. Use a wet or circular saw with a masonry blade to cut away the stones if necessary. Spread mortar onto the second section of stone and place it on the wall next to the first section. Continue placing stone sections over the entire wall.

Push mortar deeper into the joints approximately 30 minutes after you set the first sections in place with a rounded stick. Some excess mortar may fall out at this time. Use a whisk broom or wire brush to remove the dry mortar from the face of the precast stone.

Mix together 1 part cement and 2-1/2 parts fine sand. Add enough water to made grout that will flow easily out of a grout bag. Use a bag with a 5/8-inch opening and fill it halfway with grout. Inject grout into the joints between sections. Let it dry until you can leave a thumbprint in it. Use a jointer tool to straighten the grout in the joints. Brush any excess grout off the face of the stone wall once the grout is completely dry.