extra underlayment for laminate with preattached underlayment
We bought the costco laminate with preattached underlayment for first floor that is concrete slab. I am thinking to put an extra layer of underlayment for better insulation. I was recommended to use "selitac underlayment".
I wonder would the extra underlayment cause any problem in the long run? 'Cause I image the floor would not as freely to float because the friction between the layments. If yes, what is a good way for extra insulation? If no, is selitac a good choice? It is about $50 per 100 sqft.