How to Build a Laminate Countertop With Under-Mounted Sinks

Measure and cut plywood to the size of your countertop. The front edge of the counter should overhang the cabinet base by 1-inch. Use a table saw to cut the plywood.

Turn the plywood upside down. Measure the length of the front edge of the counter top. Cut a 1-inch plywood strip to this length. Apply a bead of carpenter's glue along the flat side of the strip. Position the strip even with the front edge of the plywood and aligned with the ends. Screw the strip to the plywood with a screw every 6 inches. The screws should not come through the top of the plywood.

Turn the plywood right side up. Place the plywood over the cabinet base and locate the sink cabinet. Measure the cabinet width and divide the measurement in half to find the center of the sink. Mark the edge of the plywood. Use a straightedge to draw a line across the width of the plywood showing the center-line of the sink.

Place the undermount sink template over the center-line marks. The sink needs to be far enough back from the front edge to be inside the sink cabinet and far enough from the back edge to allow for faucets. Draw the outline of the sink onto the plywood.

Drill a hole through the plywood inside your outline. Use a jigsaw starting in your hole to cut out the sink. Set the board aside for later. Screw two temporary braces across the sink hole. Turn the counter upside down. Fit your sink into the sink opening. The braces will hold it flush.

Cut four pieces of 1-inch plywood strip into sections that will fit around the perimeter of the sink. Apply glue to the face of the strip. Position the strip face down over the lip of the sink and the lip of the underside of the plywood. Screw three or four screws through the strip into the plywood for each strip. The strip sizes are not critical. Usually, the two strips are shorter than the width and two strips are longer than the length, so all can be easily secured into place. Screw one strip along each side of the sink. Turn the counter over and unscrew your braces.

Apply tape around the inside edge of the sink. Mix and apply a thick coat of auto body putty from the inside edge of the sink to 2-inches over the plywood. This coat is usually about 1/8-inch thick close to the sink. Completely cover the seam area. Smooth the putty with a putty trowel or piece of cardboard. Taper the putty from the sink to the plywood. Allow the putty to dry completely. Sand the putty and surrounding areas smooth with a band sander.

Unroll the laminate sheet. Clamp the laminate to the countertop. Cut around the perimeter of the counter using a router with an oversize bit so the laminate is 1/2-inch larger than the plywood on all sides. Stick your hand through the drain hole in the sink from the underside and draw the outline of the sink on the underside of the laminate using a pencil. Remove the laminate.

Tape around the top edge of the sink to protect the sink from excessive adhesive. Place the wood cut out of the sink outline you cut earlier, over the sink and weigh it down with something heavy. Paint the top of the counter with laminate adhesive. Paint the underside of the laminate with adhesive. Allow the adhesive to dry. Remove the wood, weight and edge tape.

Place wood dowels every 3 inches across the counter. Position the laminate on the dowels so it doesn't touch the counter. Center the laminate on all sides for full counter coverage. Remove the center dowels and press the laminate into the counter. Smooth from the center to the sides. Work from the center toward the ends, removing dowels and pressing the laminate and counter together. Finish by rolling a hard roller over the surface.

Router along the perimeter of the plywood using a tight-cutting tip. Make a hole in the laminate over the sink and router around the edge trimming the laminate tight to the inside of the sink. The inside tape you positioned earlier should protect the inside of the sink from marks.

Cut laminate strips for the front edges. Apply laminate adhesive to the front plywood face and the back side of the laminate. Press the two together. Use clamps to hold the laminate in place while you router the top and bottom edges. Place tape every 4 to 5 inches across the laminate edge to hold the laminate while the adhesive dries completely.

Sand the inside edge of the laminate around the sink edge to create a smooth transition.