Undermount Sink & Granite Tile Countertop Installation

Measure the length and width of the cabinet base for the countertop installation with a tape measure. Use a straightedge to transfer the measurements to a 1/2-inch plywood board using a piece of chalk to mark the cutting lines onto the plywood surface. Cut the plywood along the marked lines with a skill saw, then secure the wood to the cabinet base with wood screws, countersunk below the surface of the board.

Mark the cabinet measurements using chalk on a piece of backer board, then cut the board with a skill saw along the marked lines. Mount the backer board onto the plywood using thinset mortar as an adhesive, spread onto the plywood with a trowel. Secure the backer board further using drywall screws, also countersunk into the board surface and spaced every 8 inches.

Place the template for the undermount sink over the backer board in the desired mounted position. Leave room behind the sink position for the placement of the faucets. Trace the template position onto the countertop with the pencil, then remove the template.

Drill four holes through the countertop inside the four corners of the template. Place the blade of a jigsaw through one of the holes, then cut through the backer board and plywood along the traced template lines to make room for the undermount sink. Use the drilled holes at each corner to maneuver the saw blade so you can cut along the next line on the template outline. Remove the cutout from the countertop, then wipe off any residue from cutting through the counter with a damp cloth. Use a hole saw attached to the drill to drill the holes for your faucet mounts where needed through the countertop, depending on faucet type.

Position the granite tiles over the countertop, lined as you wish to place them. Use tile spacers between the tiles to create room for grout between the tiles. Mark a chalk line onto any tiles requiring cutting in order to fit on the edges of the countertop, and around the cutout for the sink. Cut the tiles along the marked lines with a tile wet saw. Remove all the tiles and place onto a flat surface in the chosen positions.

Cover the backer board with a layer of thinset mortar using the notched trowel. Tilt the trowel on edge, at about a 45-degree angle, and go over the mortar with the notches to create ridges in the mortar for better adherence to the tiles. Return the tiles to the board surface, using the arranged placement, with the tile spacers between the tiles to create the joints for grouting. Put a carpenter’s level across the tiles to check that they’re level with one another. Adjust the tile height as needed to level them by pressing down on high tiles and adding mortar to the base of low tiles. Wait overnight for the thinset to begin to set.

Remove the spacers from between the tiles and spread the grout over the tiles into the joints with a grout float. Remove remaining grout from the face of the tiles with a damp sponge, after you finish filling the joints. Wipe the tile surface an hour later with a lint-free cloth to take off any grout residue.

Cover the sides of the countertop with small granite skirt pieces, extending from the top of the counter to the base of the plywood layer. Use the thinset to set the skirt tiles in place, and then tape them in place with masking tape to secure them as the mortar begins to set. Allow the mortar to set overnight, then grout the joints between the skirt pieces using the same process used with the full tiles on top of the counter.

Allow the thinset and grout two weeks drying time.

Spread a bead of silicone caulk along the rim of the undermount sink. Press the sink to the bottom of the countertop with the sink opening aligned with the hole in the counter. Place the mounting clips included with your sink over the edges of the sink and the bottom of the countertop, using at least two clips per sink side. Screw the clips in place with 3/4-inch buttonhead screws through the mounting holes of the clips into the countertop. These clips will further secure the sink in place.

Fill the joints between the tiles and the wall with caulk to aid in waterproofing the joint.

Allow the grout and mortar to set for seven days. Remove the tape, then brush tile and grout sealant over the grout lines to waterproof the grout further and to prevent staining. Allow the sealer 48 hours to dry before using the countertop.