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How To Install Undermount Sinks In Laminate Countertops

March 21st, 2011 Leave a comment Go to comments

You are going to need to watch the videos that demonstrate how to install undermount sinks with Formica counters. HD Wilsonart plastic laminate integral sinks have three methods of installation. How you install the under-mount sink will depend upon the countertop style you are working with.

There are three different videos on Youtube:

  1. Installing under-mount sinks in post-form counters
  2. How to install an undermount sink before the plastic laminate is glued on, the filler method.
  3. How to install an integral sink using the spray method

Tools or Materials Needed:

Plastic Laminate Integral Sink


  • Belt Sander
  • Screw Gun
  • High-speed Router
  • Special Trim Bits
  • Jig Saw
  • ¾” Paddle Bit
  • Denatured Alcohol
  • Clean White Rags
  • Surface Leveler
  • Spray Method For Installing an HD Integrated Sink

The box label identifies the sink design and color, Make sure you inspect your sink to ensure that there are no flaws in it.

Most HD undermount sinks are marked for center faucet placement to help with the installation of plumbing fixtures. Also, a slight indentation is included in the front wall of every vanity sink to indicate the overflow location.

Check for flatness of the sink flange, on a flat work surface.

Mark the sink location on the countertop substrate with a set of vertical and horizontal lines. Align the registration marks on the flange with your center lines. With a marking device, trace the sink’s perimeter leaving an eight inch gap between the marked line and the rim of the sink.

Using a three quarter inch paddle bit, drill a hole on the inside of the outline. This will be the starting point for your jig saw.

Using a jig saw, cut the countertop along the marked outline of the integral sink. Keep the cut-out for the plastic laminate bonding process.

Index the laminate with the substrate. With a marking device, trace the inside of the cutout on the backside of the Formica.

Dry fit the under-mount sink in the cutout. Ensure that there is an eight inch gap or less between the sink edge and the inside edge of the cut-out.

Place the cutout piece you saved on the Formica and align it with the traced lines. This will eliminate getting contact adhesive in this area when you are spraying the glue.

Apply the countertop contact adhesive, first to the backside of the plastic laminate, then to the substrate or raw countertop deck.

Index the plastic laminate using spacers like dowel rods. A j-roller is recommended for applying adequate pressure to the laminate surface.

Dry fit the undermount sink in the cutout and make sure the sink flange doesn’t extended beyond the substrate.

Drill a three eights inch hole two inches in from the inside edge of the cutout in the laminate. This will be used for the router bit to extend through when trimming the plastic laminate.


Using a clean white cloth, clean the under-counter sink flange and exposed laminate with denatured alcohol. Be sure to remove ink printing on the backside of the Formica at bonding locations.

Prep your sink seam adhesive by slowly purging the cartridge before attaching the mixing tip. Additionally, purge the tip to ensure proper mixing of the adhesive. Run a small test bead on a small piece of laminate to let you know when the adhesive has dried.

Apply a single three sixteenths inch bead along the inside edge of the sink flange.

Place the sink in the cutout and wiggle the sink to distribute the adhesive.

Align the under-counter sink with the marks on the flange and the register marks on the countertop. Apply firm pressure for about ten seconds. No weights are necessary.

If the sink flange is not level with the countertop substrate, use a router or surface leveler to remove excess.

Fill the gap with one hundred percent silicone. Fasten two inch wide by three quarter inch thick wood strips, one half inch over the integrated sink flange. Use yellow glue and secure them with a staple gun or with screws.

There are three basic ways to route and profile the Formica plastic laminate:

-Wilsonart HD sink router bits
-A laminate tilt base router with a bottom bearing bit
Art Betterly acrylic sink trim router

Refer to the installation guide for specific use of the tools related to each installation method.

In the video above the Wilsonart HD router bits are used.

Using the Wilsonart HD straight trim bit, cut out the center section using a trim router. Moving the router in a clockwise direction, apply moderate pressure to the bevel edge of the sink. Use medium speed to move the router. Make sure to support the center laminate section while routing. It should be held flat and not sagging while making the router cut.

To easily set the depth of the router bit so that it doesn’t come in contact with the router deck, place a Formica laminate chip or scrap laminate on the faucet-deck of the integral sink and allow the bearing to rest on the laminate sample. Tighten the router base and you are ready to go.

Using a variable speed router between sixteen and eighteen thousand RPMs will prolong the life of the carbide router bits.

Profile the laminate using the HD beveled profile bit. This will provide a close cut to the bevel of the sink and in some cases slightly cutting into the sink itself.

Together these two bits will minimize sanding and tool wear in the next step.

When finished with the bevel edge use a random orbital palm sander, starting with one hundred fifty grit and finishing with two hundred twenty grit sandpaper.

Finish out the sanded bevel using a grey 3M Scotch Brite pad.

To activate the overflow, locate the indentation on the front of the undermount sink. Use a three eights or half inch paddle bit and gently drill through the acrylic surface, taking care not to drill too far past the acrylic layer.

Sand the overflow hole to remove sharp edges.

This concludes the spray method installation for the undermount plastic laminate sink. Please refer to the other Wilsonart videos for installing under-mount sinks with Formica laminate countertops.

Categories: Making Counter Tops
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