How to Fasten an Undercounter Sink to a Granite Top

Spray a small amount of granite cleaner onto a cotton cloth and use it to wipe down the underside of the granite around the opening of the sink cutout. Wipe away any stone dust or construction debris that may have accumulated there. Dust could prevent the silicone and epoxy from bonding properly.

Squeeze a thin line of silicone caulk adhesive onto the bottom of the granite counter just inside the edge of the sink cutout. Line up the rim of the sink below the counter with the cutout and push it securely into place from the bottom. Hold it in place for a moment to give the silicone a chance to grab.

Place a 2x4 board across the top of the granite, stretching across the sink and sink opening. Insert one end of the C-clamp into the drain on the sink and the other end over the top of the 2x4. This will hold the sink in place while the epoxy and silicone are drying.

Place a small amount of epoxy on the underside of the granite just outside the edge of the sink's rim. Place the post of the sink mounting clips in the epoxy and hold for a moment until the epoxy grabs. Repeat at regular intervals around the perimeter of the sink until all posts are installed. Allow the epoxy to begin to set up for 10 minutes.

Apply a small amount of epoxy directly to the sink's rim directly opposite each of the posts. Attach the clip portion of the sink mounting clips onto the sink so one end fastens down over the post. If a bolt system is used, tighten this down with the adjustable crescent wrench until it is secure; do not over tighten. Repeat until each post is secured to a clip.

Wait several hours before removing the 2x4 and C-clamp. Wait at least 24 hours before hooking up the waste pipe or any disposal units to the sink.