We are going to install 20mm laminate flooring and I heard that the underlayment is just a sound buffer. We currently have subfloor that is pretty flat and even. Can I omit the underlayment? What are the disadvantage of doing so? The laminate flooring will not have glued on back underlayment either. It will be a floating floor.
yes, but I believe the proper term is called sub flooring.
the foam underlayment will help deaden sound, true, but more importantly, since the floor floats, it will prevent the two hard surfaces from squeeking against each other.
No you do not need any other underlayment. It is a bad idea to double up on padding because this will cause the joints in the floor to flex more and weaken the tongues, causing eventual board separation. It's very important that you use the 6 mil plastic for vapor barrier. Rosin paper is useless over concrete. Overlap the plastic a few inches and tape the seams and you should be fine. Feel free to email any other installation questions
Yes, because the floor is a floating floor and not fastened you will get the laminate clacking on the sub floor especially if your floor is not perfectly level or even and that will drive you crazy. If you don't care about moisture barrier just buy any cheap laminate foam pad should run about 10 cents a square foot. More expensive pads have add ons such as poly membranes for moisture barriers and sound suppression underlayments to eliminate sound transference in the room as well as to areas below as well.
No, you may not omit the underlayment. Laminate floors are designed to float freely. If you do not install the underlayment for the laminate to float on the movement of the floor could be impeded and the floor could buckle or peak. Underlayment is very inexpensive. Upgraded foam will help to control a hollow clacking sound under the floor. At least get the cheap foam but I recommend the upgraded foam for acoustics. Unless you plan to invest in some serious coverage in area rugs. Also remember not to permanently attach anything to the floor or again the movement could be restricted. All laminate floors require a 1/4 gap around the perimeter of the whole floor including at the transitions. If you don't the floor will expand and the seams will peak or lift. Install quarter round to your existing baseboard to cover the 1/4 gap. In wet areas like the floor in front of the sink be sure to lay a bead of silicone in the gap to prevent moisture from getting in the core or under the floor. Good luck with your project I hope it helps, Jen
