How to Install Foam Underlayment for Laminate Floors

Inspect and repair the subfloor, as needed. If the home uses a plywood subfloor, drive all loose nails into the subfloor with a hammer. If the plywood subfloor squeaks while walking across it, drive additional 2-inch ring-shank nails through the subfloor and into the floor trusses. If the home has a concrete subfloor, float all visible dips or valleys in the subfloor with a self-leveling concrete compound. Use the concrete compound manufacturer's mixing and application instructions.

Measure the thickness of a piece of laminate flooring and the foam underlayment, using a tape measure. Add the two measurements together and transfer the total to a jamb saw's blade guide, using the jamb saw manufacturer's instructions to adjust the blade guide's height. Most jamb saws have a ruler on the blade guide that indicates the blade guide's height and a thumb screw that holds the blade guide in place.

Cut the trim at the bottom of each door jamb, using the jamb saw. Discard the cut piece of trim. Removing the small section of trim at the bottom of the door jamb allows the laminate flooring to wrap around the door jamb without leaving a large amateurish-looking gap.

Remove any debris deposits from the subfloor, using a floor scraper to shave the subfloor's surface. Run the floor scraper over the entire subfloor. Clean the loose debris from the subfloor with a broom and dust pan, paying special attention to the gaps below the door jamb trim and near the walls.

Unroll the proper type of foam underlayment next to the room's longest wall, starting the end of the underlayment roll at one corner of the room and extending it to the longest wall's far corner. Cut the foam underlayment to size at the longest wall's far corner, using either a utility knife or scissors. If using combination foam underlayment, keep the underlayment's plastic coating facing the subfloor. Either side of standard foam underlayment can lay on the subfloor.

Cover the room's remaining subfloor with the foam underlayment, using the same method used on the underlayment's first row. Butt the edge of each additional underlayment row against the previous underlayment row's edge. Do not overlap the foam underlayment's seams.

Cut a scrap piece of foam underlayment to fit around the door's threshold, using either the utility knife or scissors to custom-cut the underlayment to size. Set the threshold's underlayment in place. If the room has any nooks, custom-cut a piece of underlayment to fit the nook and set the underlayment in place.

Cover each seam in the foam underlayment with a cloth-backed duct tape. Secure the edge of the foam underlayment at the door threshold to the subfloor, using the duct tape. If any piece of the underlayment will not lay flat on the subfloor, secure its raised edge to the subfloor with the duct tape.