Underlayment can help with a wide variety of issues, such as sound control in a cement floor application or cold floors in a basement for example. Without underlayment to add a layer between these damp subfloors and the surface flooring, your laminate can quickly become wet, warped, and mildewy, harming its overall integrity. Moisture over time can also break down floor adhesive which causes the floor to start warping. If you want to get the best performance and long-lasting quality from your laminate floor, you need to install it with an underlay.
Why put underlayment over concrete?
Even though it looks solid, it is actually very porous, thus moisture can easily penetrate it. Any flooring laid directly on top of the concrete for example like carpets/wood flooring will be susceptible to moisture buildup. Proper insulation of concrete flooring can help eliminate its moisture problem. After cleaning the concrete surface, you'll need to add a vapor barrier. This is a necessary step before installing any floating floor over a concrete subfloor. After this is rolled out, you're ready to install your new flooring.
Do you need underlayment over tile?
You can assume a moisture barrier is beneath the tile layer, and if not, the tiles themselves act as one. However, it's also wise to lay underlayment under the laminate flooring to provide a warm underfoot and better moisture protection.
But Yes; you can install laminate flooring over a ceramic tile floor if the tile floor is in good condition and the tile is well attached, level, and flat.
Depending on your subfloor we have 3 different levels of underlayment.