How Are Undermount Sinks Mounted?

Undermount sinks can give your kitchen or bath a sleek, modern look, but they must be installed correctly. An undermount sink with a garbage disposal and completely filled with water can weigh nearly 100 lbs. An incorrect installation could cause the sink to fall from the countertop or cause it to leak when filled. An undermount sink can install to any type of countertop, provided the sink hole is cut for the installation of undermount sinks.

Things You'll Need

• Silicone caulk
• Bar clamps
• 2-inch-by-4-inch board
• Two-part epoxy
• Phillips or slotted screwdriver
• Drill
• Wood drill bit

Instructions

Stone Countertops

1. Apply silicone caulk to the lip of the undermount sink. Remove the clamp ends from two bar clamps and thread the bars through the drain holes.

2. Place a 2-inch-by-4-inch board over the sink hole and on top of the countertop. Replace the clamp ends onto the bars and attach the bar clamps onto the wood to hold the sink in place under the countertop.

3. Go beneath the countertop and the sink. Mark the location for the sink clamps onto the underside of the countertop.

4. Purchase a two-part epoxy rated for damp environments, moisture resistance, rapid curing and at least 300 lbs. maximum capacity. Mix the epoxy according to the directions of the product.

5. Clean the underside of the stone countertop to make sure no stone dust is present. Attach the undermount sink clamps to the underside of the countertop with the epoxy. Allow the epoxy to dry for the time recommended by the manufacturer.

6. Screw the mounting bolts into the clamps to secure the sink to the clamps. Remove the bar clamps for the sink.

Solid Surface or Laminate Countertops

1. Run a bead of silicone caulk along the lip of the undermount sink. Clamp the sink beneath the countertop.

2. Lay a 2-inch-by-4-inch board across the top of the sink and the countertop. Remove the clamp ends from two bar clamps and thread the bars through the drain openings in the sink. Replace the clamps on the bars and attach the clamps to the boards to hold the sink in place.

3. Mark the locations for the undermount sink clamps onto the underside of the countertop. Drill holes into the underside of the countertop using a wood drill bit sized to equal the width of the female inserts for the undermount clamps. Drill the depth of hole equal to the length of the inserts. Use a drill stop to make sure each hole is the proper depth.

4. Purchase a two-part epoxy designed for adhesion to wood that's moisture resistant. The epoxy needs to be quick-setting and should hold at least 300 lbs.

5. Mix the epoxy according to the direction and glue the inserts into the countertop. Allow the epoxy to dry from the time recommended by the epoxy manufacturer.

6. Clamp the undermount sink to the countertop. Place the metal clamps onto the sink and install the screws through the clamps and into the inserts, securing the sink to the underside of the countertop.

References

• Home Construction and Improvement: How to Install Undermount Sinks; Todd Fratzel
• Stainless-Sink.com: A How to Guide for Installing a Stainless Steel Undermount Sink and Clips
• Blanco: Undermount Sinks Installation Instructions
• Plumbtile: How To Install an Undermount Sink; June 2010
• Ask the Builder: Undermount Kitchen Sinks; Tim Carter