How to Seal an Undermount Sink

The key to the successful installation of an undermount sink is a secure seal. Undermount kitchen sinks are sealed to solid surface countertops with silicone caulk as they are installed. Once the sink hole is cut, you are ready to seal the undermount sink. Work carefully to ensure proper positioning of the undermount sink. Once the seal dries and the clips are in place the sink is difficult to move again.

Rag
Denatured alcohol
2-by-4
Silicone caulk
Bar clamp
Putty knife

Instructions

- 1
  Wipe the underside of the sink's lip clean with a rag moistened with denatured alcohol to remove all surface dust and debris.
- 2
  Place a 2-by-4 over the sink hole. The 2-by-4 must extend past the sink cutout by at least 3 inches on each side.
- 3
  Run an uninterrupted bead of silicone caulk around the lip of the undermount sink.
- 4
  Have a partner press and hold the undermount sink in place on the underside of the sink cutout.
- 5
  Install a bar clamp. Run the bar through the drainage hole in the sink. For double sinks, install two bar clamps, one through each drainage hole. Tighten the clamps at the underside of the sink and the top of the 2-by-4.
- 6
  Adjust the placement of the sink if necessary.
- 7
  Tighten the bar clamps. Epoxy the undermount clips -- provided by the sink's manufacturer -- in place as per the sink manufacturer's instructions if they are not already in place. Tighten the clips onto the sink while the caulk is still soft. Scrape off any excess caulk with a putty knife. Wipe the area clean with a damp cloth.
- 8
  Allow the caulk to cure and finish installing the sink.

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