How to Work With Manufactured Stone
If the words “manufactured stone” conjure up images of a fake that you can spot a mile away, then you need to take a look at modern manufactured veneer stone. Today’s versions look so good that you’ll be hard-pressed to tell them from actual stone. And since manufactured stone is cheaper and lighter than the real thing, it’s a great choice for any stone veneer project.
We enlisted Marcus Schilling, a third-generation mason, to show us how he installs stone veneer. You can use manufactured stone indoors or out, but exterior applications require special attention to details of waterproofing and flashing. Before installing exterior stone veneer, talk to your local building inspector to see what’s required in your area.
Easy way to cut wire lath
Wire lath can be unruly, and the cut edges are sharp. So anything you can do to keep the stuff under control while you’re cutting it is a big bonus. Here’s a tip from Marcus on how to make long cuts. Lay the wire lath on some long boards. Measure from the edge of the lath to the edge of the board on each end so the desired cutting line is lined up with the edge of the board. Then secure the lath temporarily with a few staples. Now use the edge of the board as a guide to make the cut. Marcus uses cordless metal shears, but tin snips or aviation snips will also work.
Marcus swears this is the fastest way to get the mud on the wall. Prop up your mud board about 16 in. high and within easy reach. Load it with mortar. Then use your London trowel as shown to transfer the mortar from the mud board to your trowel. Pull the trowel up the wall to embed the mortar in the lath.
You don’t need a special tool to scratch the mortar
Grooving or scratching the wet mortar provides a better bond for sticking on the stones. You can buy a special rakelike tool for this, but Marcus prefers to use a 3/16-in. square-notched tile mastic trowel. They’re cheap and easy to find at home centers and hardware stores. Simply drag it across the wet mortar to make horizontal stripes.
Create a suction cup
Marcus makes a swipe across the entire back of the stone with the trowel first to create a good bond for the mortar bed. Then he wipes mortar from the trowel all around the perimeter. This creates a little hollow spot in the middle that will act as a suction cup to hold the stone in place until the mortar hardens. The key is to put on enough mortar to create about a 1/2-in.-thick layer when the stone is pressed against the scratch coat. If any mortar oozes out around the edges, knock it off with the trowel so it doesn’t get in the way of grouting.
Disguise the cut ends of stones
Occasionally you’ll have to cut stones to fit. Marcus uses a 10-in. chop saw equipped with a dry-cut diamond blade. But if you’re doing only one job, you can get by with a diamond blade mounted in an angle grinder. Regardless of the tool you use, you’ll want to disguise or hide the cut ends. After cutting a stone, Marcus cuts angles on the corners to make them look more natural. You can also use a tile nipper or horse-hoof trimmer to chip away at the sharp edge left by cutting. Marcus chooses thin stones to cut if possible. Then he hides the cut edge against a thicker stone. And if he’s using mortar that’s dyed to match the stone, as you would in a dry-stack installation, Marcus butters the end of the stone so it blends in better.
Cut off the tip of the grout bag
Grout bags come with either metal or plastic tips. Marcus prefers the plastic tips for grouting stone. He cuts the tip to create an opening that’s about 5/8 in. in diameter to allow proper mortar flow. Marcus says a common mistake is to mix grouting mortar too stiff. Make sure the mortar is loose enough to ooze from the tip without having to squeeze the bag.
Rinse the bag to avoid clogs
Marcus recommends rinsing out the bag after every third bagful of grout. Otherwise sand builds up along the edge, clogs the tip and makes grouting difficult. Just fill the empty bag with water and rub it back and forth to dislodge the caked-on grout.
Fill the joints completely
Marcus says he often encounters hollow grout joints on work done by beginners. Be careful to fill the joints full from back to front as you’re grouting. Joints that are hollow underneath will fall out later. Keep the tip pressed deep into the joints so they get filled from the back to the front of the stone.
You don’t need a special tuckpointing trowel
Marcus finishes the joints using a 3/8-in.-wide tuckpointing trowel that he’s cut off to about 5 in. long. He says most masons prefer the shorter length because it gives them much better control. But he says a carpenter’s pencil is a great alternative. It’s the perfect size and shape for striking your grout joints. Let the grout set up until it’s firm to the touch, but not completely hardened. Usually this is about 20 to 30 minutes. Then rake the pencil over the grout to smooth and shape it. Finish up by brushing off any loose mortar with a soft masonry brush.
Wait! Don’t wipe off that wet mortar
When you spill a glob of mortar on the stone, which is almost certain to happen, leave it alone. Let the mortar set up about 30 minutes. Then flick the partially hardened mortar off with the tip of the trowel. Dab the remaining residue with a damp rag to remove it.
Meet the Expert
Marcus Schilling was introduced to the world of masonry when he was only about 7 years old. He helped his dad with all sorts of stonemason tasks, including carrying small stones and cleaning up at the end of the day. And he loved it from the start. His grandpa was a stonemason. His grandpa taught his dad, and his dad taught Marcus and his brothers. And now Marcus is teaching his sons—and us!—the craft of setting stones and laying bricks.
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