Underlay comes in many materials and densities. Take time to consider the wide variety of options that are available to you.
If you have children, dogs or downstairs neighbours then opt for noise-reducing polyurethane foam or cork underlay to diminish the hollowed out sound of feet running across the floor.
Reduce heat loss by choosing an underlay with good thermal insulating properties for concrete subfloors. In kitchens and other work areas, a thick foam version can be more comfortable during long spells of standing or walking. For areas with heavy furniture or exercise equipment, a denser style will reduce indentations and wear on carpet.
Prepare the Floor
Before starting, make sure that the subfloor is flat and free of obstructions or remnants of the old flooring. Use needle nose pliers to remove staples. Small nails are easy to miss and can wreak havoc on your flooring installation, so get down on your knees and examine the floor closely. Sweep the floor thoroughly before putting down the underlay.
Lay a Moisture Barrier
A moisture barrier is necessary to prevent condensation from forming between a concrete subfloor and your new flooring. Without a barrier, moisture can accumulate on the underside of flooring and cause mildew or rot. Moisture barriers are typically sheets of clear plastic film that are put down before the underlay. Some underlays come with a coating which serves as the moisture barrier. This type of underlay should be installed with the barrier side facing the subfloor.
Roll out the moisture barrier in strips that overlap each other by twenty centimetres. Use a plastic tape to attach the sheets so that they do not slide around while you work.
Do not install a moisture barrier over a wood subfloor as it may trap dampness and cause problems with mildew or warped floor boards.
Laying the Underlay
Roll out the underlay in a straight line from one end of your starting wall to the other. When you get to the end of the wall, use a knife to cut the underlay. Lay the next row so that it butts up against the edge of the first row, but does not overlap. Tape the edges together so that they cannot shift.
For carpet flooring, the underlay should be cut to fit the room and extend over the carpet grippers. For all other flooring, cut the underlay so that it extends up the wall by four centimetres.
Underlay should not be used on laminate or hardwood stairs. If stairs are to be carpeted then the underlay should be cut to fit and stapled or glued so that it rolls over the nosing and between the strips of carpet gripper.