Proper Undermount Sink Installation

An undermount sink offers a seamless appearance.
An undermount sink offers a seamless appearance. (Image: Jupiterimages/Creatas/Getty Images)

Undermount or recessed sinks are available in a wide range of styles and materials. The sinks are fitted beneath a countertop in kitchens and bathrooms. Besides their seamless appearance, another advantage to undermount sinks is that food and other debris are easily wiped into the sink without being caught on the rim. Installing an undermount stainless-steel kitchen sink on solid surface countertops is a project that takes about an hour to complete with a moderate skill set in home improvement.

Things You'll Need

  • Acetone
  • Rags
  • Caulk gun
  • Clear or translucent silicone
  • 4-foot wooden brace
  • 2 24-inch bar clamps

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Clean the top edge or lip of the sink that will mount to the bottom of the countertop with a rag and acetone to remove dirt or grease. Repeat this step for the bottom edge of the countertop around the sink opening.

Insert the sink carefully into the cabinet beneath the opening and rest it facing upright in the bottom of the cabinet either through the sink opening or through the cabinet itself. Be careful not to damage the sink, countertop or cabinet.

Apply a 1/2-inch wide bead of material around the mounting lip of the sink, using the silicone and caulk gun.

Lay the 4-foot brace across the sink opening on top of the countertop. This brace will support the sink until the silicone properly cures.

Lift the sink up and into place so that the sink's lip contacts the bottom of the countertop.

Insert the bottom end of a bar clamp through the drain opening in the sink. The top end of the bar clamp slips over the brace. For double sinks, repeat this step for the other side of the sink. The brace and bar clamps now support the weight of the sink.

Tighten the bar clamps to lightly make the sink snug to the countertop. It is important not to tighten them too much at this time to allow for sink adjustment.

Adjust the sink until it aligns correctly with sink opening. The countertop will overhang the sink or it will line up flush with the sink. It is important to maintain the same distance around the sink in either scenario for appearance.

Tighten the bar clamps until the sink is tight to the bottom of the countertop. Inspect the seam so that there are no voids that require silicone. Carefully tool the silicone completely into the seam joint. Remove any excess silicone with a rag damp with acetone. Allow the silicone to cure for at least 24-hours before removing the clamps and brace.

Tips & Warnings

  • Use acetone to clean up any excess silicone before it dries. Once it dries, it is much harder to remove.
  • Recruit a helper to help install the sink. Although this project is possible with one person, an extra set of hands makes it much easier.
  • Follow the warning labels on the acetone bottle.
  • Use proper ventilation when using silicone and acetone.


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