Fastening an Undermount Sink to the Countertop

It’s risky to rely on just glue, however, if you’re installing a heavier porcelain, cast iron or composite stone sink, and manufacturers usually supply clips for those that must be secured to the underside of the countertop with screws or epoxy cement.

What holds an undermount sink in place?

Undermount sinks are typically attached with a two-part epoxy adhesive and sealed with silicone caulking around the perimeter. Make sure to get a professional or someone who knows what they’re doing. Most professionals can install an undermount kitchen sink in 30 minutes or less.

Is silicone enough to hold an undermount sink?

Most undermount sink manufacturers recommend that you use pure, 100-percent silicone sealant for undermount sink installation. Silicone sealants are designed for resilient flexibility and have good adhesive properties. If an ordinary caulk was used to seal the sink, it likely will fail quickly.

Do you need sink clips?

A kitchen sink that does not require clamps is set directly on the countertop and is held in place with silicone caulk. Installing a kitchen sink without clamps is moderately challenging because it requires carpentry and plumbing skills.

How is an undermount sink attached to granite?

The system includes 6-8 bolts, clips, and wing nuts. The bolts are inserted into grooves that the fabricator drills or cuts into the back of the counter, spaced evenly around the flange of the sink. The clip is then attached to the flange and tightened to secure the sink to the counter top.

How do you secure an undermount bathroom sink to granite?

For most bathroom undermount sinks, all that is needed to mount the sink to the granite is a silicone adhesive. Squeeze a very thin line around the sink cutout on the underside of the granite. The weight of the sink will compress the adhesive slightly, making it spread out, so a thin line is all that is needed.