How to Install Linoleum Underlayment for a Countertop

Measure the length of the cabinets to determine the countertop length, unless you plan to cover an existing counter surface. In that case, measure the countertop, front to back and side to side.

Add an overhang measurement value to the cabinet dimensions if you are covering bare cabinets rather than an existing countertop. Most common is a standard drip edge of 3/4 inch, added to any open sides -- those not butting up to a wall. Some overhangs measure several inches without additional support such as braces.

Mark the necessary measurements, including overhangs, on a piece of 3/4-inch exterior-grade plywood. Exterior-grade plywood is more durable than interior-grade and emits a lower level of volatile organic compounds. That results in cleaner, healthier indoor air.

Cut the exterior plywood to size with a table saw or circular saw. Use the outside edge of the cut marks as a guide to ensure your plywood isn't shorter or narrower than required.

Lay the plywood on top of the cabinets, aligning it as necessary. Set a level on top, running from front to back, side to side as well as corner to corner. Wedge thin shims under the plywood, resting on top of the cabinet edges, corner supports or previous countertop as applicable, to level the surface if needed. Check for level again before proceeding.

Measure in from the countertop edge the amount of the overhang, if applicable. Mark the top of the countertop to signify the location of the cabinet walls beneath. Run a straight edge to mark this line, where you will attach the plywood to the cabinets.

Drive screws through the plywood into the cabinet walls beneath, using the cabinet wall line previously marked as a guide to the edge of the cabinet wall. Attach every 6 to 8 inches. Add screws driven up through the cabinet into the plywood above, if feasible. Use the proper length of screws, according to your circumstances, to ensure you do not penetrate the entire depth and leave sharp objects sticking out.

Locate the sink opening, measuring over from the edge, both lengthwise and depth-wise, to determine the proper sink location based on your needs and plumbing below. Align and tape down the sink template, a guide provided with the sink to allow you to cut a precise opening. Alternatively, use the sink opening of your existing countertop to determine where to cut.

Drill a hole just inside the outline indicating the edge of the sink area. Using this as a pilot hole, cut the plywood out of the sink area with a jigsaw. Hold the wood up as you work to ensure it doesn't sag and bind the saw blade.

Measure and cut a piece of backerboard to the same countertop dimensions used for the plywood. Score the backerboard, running a utility knife along the straight edge, on both sides of the board. Bend to break, as you would break drywall.

Align on the backerboard the piece of wood you cut from the plywood to allow for the sink. Ensure it is positioned precisely, lengthwise and depth-wise. Run a pencil around the sink template to mark the backerboard.

Score the backerboard along the sink outline with a utility knife on both sides of the backerboard. Alternatively, use a nail punch. Tap the backerboard cutout with a knife, aiming just inside the outline's edge to break the sink area free.

Attach the backerboard to the plywood substrate, using galvanized screws. Space the screws every 6 inches, approximately, in rows covering the entire length and width of the countertop substrate. Countersink the screw heads to drive them slightly beneath the surface.

Spread a small amount of thinset mortar across each screw head. Allow it to dry, then sand smooth with the surrounding surface. This prevents the depressions caused by the screws from showing through the linoleum countertop finish.