How to Install Stone Veneer on Wonderboard

Stone veneer on a wall.

WonderBoard is a fiberglass-mesh-reinforced cement surface suitable for interior or exterior installation of stone veneer. In addition to providing a solid surface, WonderBoard is also moisture and mold resistant.

1. Attach metal lath to the WonderBoard with exterior screws if required by the stone veneer manufacturer. Wall anchors are not required since the screws will be held firmly in place by the WonderBoard. Attach lath starting from the center and pull firmly toward the edges to prevent buckling.

2. Mix mortar according to package directions and spread a ¼-inch coat over the metal lath with a flat trowel. Use a mason’s rake or small garden hand rake to scratch the surface of the mortar. Allow it to dry for 48 hours.

3. Install the stone veneer by mixing enough mortar to work in sections. Do not make too much mortar and do not add water to the mortar if it begins to dry out.

4. Start from a bottom corner. Spread a ½-inch layer of mortar on the back of each piece of stone veneer and press onto the wall. Wiggle the piece to push the mortar mix into the scratch coat. Maintain a consistent space for grout between each adjacent piece of stone veneer. Allow the surface to dry for 48 hours.

5. Mix grout according to package directions. Pour it into a grout bag and squeeze a bead of grout into the joint between each piece of stone veneer. Smooth the grout with a grout tool, which is a narrow trowel sold in home-improvement stores. Place the tip of the tool onto the grout and gently press the grout smooth in the joint.

Tip

Grout can be made with 1 part cement mixed with 2 1/2 parts fine sand, which is also called "plaster" sand. Premixed mortar, available from home-improvement centers, also can be used.