Getting Started. Unlike other masonry, install most manufactured stone starting from the top of the wall and working downward. These stones are light enough to stick without support, and by starting at the top you avoid dripping mortar onto finished stone areas below. However, if you are laying stone to achieve a "dry-stack" appearance, you will have to install stone courses starting at the bottom and work carefully to avoid staining the stone with dripping mortar as you work your way up the wall.
Either way, install corner pieces before installing stones on the open areas of the wall surface. This makes it easier to fit your other stones into place later. Corner pieces come with short and long returns; alternate these in opposite directions on the wall.
If any mortar accidentally gets on the stone face, don't wipe it off with water, which will cause it to smear and stain the surface; instead, allow the mortar to dry and then brush it off with a dry whisk broom.
Fitting. When working with quarried stone styles, you'll need to keep the courses level. Snap chalk lines about every 4 to 8 inches as a guide, and then use a small level to set each piece.
Don't forget to stagger joints both vertically and horizontally. Stones look best with uniform grout lines of about 1/2 inch or less. Avoid long, unbroken grout lines when placing fieldstone, river rock, and other variable-sized stones.
Trimming. You can cut and shape stones with a brick hatchet, wide-mouth snips, or by striking them with the edge of your trowel. For long, straight cuts, use a circular saw with a diamond masonry blade. Although good quality manufactured stone has uniform coloring all the way through, you should always turn any cut edges away from view.
Applying Mortar. Using a mason's trowel, coat the back of each stone with a 1/2-inch-thick layer of mortar and then, using a gentle wiggling action, press the stone firmly into place. It's okay to allow a little mortar to squeeze out along the sides of the stone.
It's especially important to make sure there's enough mortar behind every stone when laying up a joint-less dry-stack installation, since the bedding mortar must hold the stone without grout. Apply a generous amount of mortar to each stone and then clean off the excess with a margin trowel, making sure to fill any voids.
If you're setting manufactured stone on a hot day or in an especially dry climate, it's a good idea to dip each stone into a container of water and let it dry for a few minutes before placing it on the wall. This ensures that the stone doesn't absorb moisture from the mortar too quickly for the mortar to set up properly. When working with joint-less dry-stack materials, you should dampen the stones regardless of weather conditions so the mortar doesn't stick to the face of the stones.
Grouting. After the stone has set, carefully apply mortar using a grout bag, taking care not to smear grout onto the stone surface. Once the mortar joints have become firm (after about 30 to 60 minutes), use a wooden or metal striking tool to rake out excess mortar and work grout into the joints to thoroughly seal the edges.
Cleaning and Sealing. After finishing the grout lines, use a whisk broom to smooth the joints and clean off loose mortar. At this point, brush off any drops and spots, which should come up easily. Never use a damp sponge to clean the surface or you'll stain the stone permanently. And don't use a wire brush or acid.
Fernando Pages Ruiz is a builder and writer in Lincoln, Neb.