Undermount sinks are often installed with solid-surface countertops such as acrylic or stone. The countertop is cut to fit the shape of the sink and the sink is installed to the underside of the countertop with epoxy or screw-in mounted hangers. The actual installation of the sink once the hangers are positioned and in place is fairly straightforward and within most homeowners' capabilities. Homeowners should provide the sink dimensions so the countertop manufacturer can cut the hole.
Attach the sink-cut countertop based on the manufacturer's recommendation. Stone-style counters are often resting on silicone or adhesives. Other types of solid-surface counters may be glued or screwed.
Cut a 2-by-4-inch-board 12 inches wider than your sink opening, using a circular saw. Place the wood across the width of the sink opening.
Lift your sink up to the underside of the countertop. Position two ratchet-type wood clamps to fit inside each drain hole and clamp to the 2-by-4-inch wood. This will allow you to hold the sink in place. Adjust the sink from the top and bottom side until you like the fit. Mark guidelines, using pencil or tape, on the underside of the counter.
Lower the sink and apply a bead of silicone along the top edge of the sink where it encounters the underside of the counter. Lift the sink back into position, using the guide marks. Check your sink position again and tighten the clamps enough to hold the sink into the silicone bead. Allow the adhesive to dry for 24 hours.
Position yourself underneath the sink inside the sink cabinet. Use the sink template to position the number of undermount sink hangers recommended by the sink manufacturer. Sink templates are included with sink packaging materials. Mark the locations with a pencil or tape.
Attach the hanger with epoxy glue or screws. The hanger should attach to the underside of the countertop and the clip part of the hanger should extend over the edge of the sink. Allow the sink to remain in place for 24 hours for the hanger epoxy to dry completely before removing the clamps and installing the faucets and plumbing.
Provide your countertop manufacturer a copy of your sink template and the measurements to the centre of your sink cabinet to have your sink holes cut. Often stone and solid surface companies will send their own personnel to measure for cuts as part of the price for having the cuts made. Buying two diamond-tipped saw blades (a hole saw and straight blade) plus renting a wet drill and saw capable of cutting stone is usually significantly more expensive than having a stone company make the cuts for you. Remove any silicone that oozes out into your sink after installation. Use a utility knife after the silicone has hardened.