Undermount Sinks Part 2 of 2

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Undermounted sinks have become quite popular in contemporary kitchens for reasons that are both practical and aesthetic. On the aesthetic side, they look updated and sleek. They are easier to clean than rimmed sinks because you eliminate that area around the rim seal where stuff always collects.

 

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Overview

Undermounted sinks have become quite popular in contemporary kitchens for reasons that are both practical and aesthetic. On the aesthetic side, they look updated and sleek. They are easier to clean than rimmed sinks because you eliminate that area around the rim seal where stuff always collects.
Most sink manufacturers make sinks that are designed for undermounting, and if you don’t mind paying the $100 to $200 premium, a true undermount sink is the best choice. But if your decision making is driven more by your frugal side, you can undermount a self-rimming (drop-in) stainless steel sink with little difficulty using readily available undermount clips. (Self-rimmers also come in a much wider range of styles.) Note: You can undermount any sink you wish, including heavy cast iron models, if you support the sink from below instead of hanging it from clips.
Not all countertops are suitable for undermounting a sink. The countertop material needs to be contiguous in nature. That is, the edges that are created when you cut through it need to be of the same material as the surface. Solid-surface, granite, butcher block, and concrete are good candidates for undermounting. Post-form and any laminated or tiled countertops are not. (Some new products that claim to seal countertop substrate edges around a sink opening are emerging, but are not yet proven or readily available.)

From: The Complete Guide to Plumbing, 978-1-58923-378-2

What You'll Need

Tools:

2HP or larger plunge router
1⁄2" template following router bit
Roundover bit
MDF or particleboard for template
Jigsaw
Drill and bits
Abrasive pads
Laminate trimmer
Belt sander
Solid-surface scraps
Solid-surface seam adhesive with applicator gun
Denatured alcohol
Undermount sink clip hardware
Silicone caulk
Pipe clamps
Pad sander

Materials:

2HP or larger plunge router
1⁄2" template following router bit
Roundover bit
MDF or particleboard for template
Jigsaw
Drill and bits
Abrasive pads
Laminate trimmer
Belt sander
Solid-surface scraps
Solid-surface seam adhesive with applicator gun
Denatured alcohol
Undermount sink clip hardware
Silicone caulk
Pipe clamps
Pad sander

 

Step 1

How to Undermount a Sink

After routing three side openings, stop routing and screw a support board to the waste piece. The ends of the support board should extend onto the template. Position the support so it is near the center, but not in the way for completing the fourth side of the cut. Then finish the cut. The support board will prevent the waste from breaking off as the cut nears completion.


Step 2

How to Undermount a Sink

If the sink outline has any chatter or the cutout is not perfectly smooth, make another pass with a straight bit before you remove the template. Remove the template and make a 1⁄8" roundover cut on both the top and bottom of the sink cutout. If you know exactly where your faucet hole or holes need to be, cut them with a hole saw and round over their tops and bottoms as well.


Step 3

How to Undermount a Sink

It’s easier to mount the sink on the countertop before you reinstall it on the cabinet. Cut several 1 x 1 mounting blocks from the solid-surface waste cutout. You’ll also need to purchase some seam adhesive to glue the mounting blocks to the underside of the countertop. After they’re cut, break all the block edges with a stationary sander or by clamping a belt sander belt-side up and using it as a stationary sander (breaking the edges reduces the chance that the blocks will crack).


Step 4

How to Undermount a Sink

Clean the blocks and the underside of the solid-surface around the cutouts with denatured alcohol. Apply solid-surface seam adhesive to the blocks and bond them to the underside of the countertop, set back 3⁄4" from the cutout. Install three blocks along the long sides of the cutout and two on the front-to-back sides. Clamp the blocks while the adhesive sets up.


Step 5

How to Undermount a Sink

Drill 1⁄4" dia. x 3⁄8" deep pilot holes for the sink clips into each mounting block. The holes should be in the centers of the mounting blocks. Tap the brass inserts for the mounting clips into the holes in the mounting blocks.


Step 6

How to Undermount a Sink

Clean the sink rim and the underside of the countertop with denatured alcohol. When the alcohol has dried, apply a bead of 100 percent silicone adhesive caulk to the sink rim. Carefully center the sink over the opening and press it in place. Hand tighten the wing nuts onto the mounting nuts to secure the clips that hold the sink bowl. Replace the countertop and hook up the faucet and drain.


 
 

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