Installing new underlayment typically is easy. Unfortunately, many do-it-yourselfers ignore this step and move directly to installation, then wished they had taken more time and installed quality underlayment. That’s because underlayment is an extra step with additional expense and the results aren’t seen -- unless the underlayment wasn’t done or isn’t sufficient.
Installing rigid underlayment means cutting the materials to fit the room and fastening them to the subfloor, typically with ring-shank or other flooring nails. Concrete subfloors will require adhesive. Make sure you use the largest sheets possible to minimize seams. Also, stagger seams for a smoother surface.
Mastic underlayment is installed with a hand trowel then leveled with a larger trowel or screed rail. As with rigid underlayment, the purpose is to produce a smooth and level surface for installing the chosen flooring material.
In extreme cases, you can install a mastic underlayment to level the floor then install rigid underlayment as a base for attaching your flooring material. It’s a lot of work, but typically the only solution for floors that are uneven and not level.
Use a floor roller from a rental center when installing rigid underlayment with adhesive to ensure a strong bond.