New Laminated Floor On An Old Floor

This is a question we often ask ourselves, and the answer depends mainly on the age of the floor on which we are going to install.
The Problem With The Old Floor
With time, these floors already by their use or antiquity begin to present cracks, dents, deformations, and in some cases, humidity. As we know in old constructions, the humidity rises through the concrete and deforms the wood. There are different types of substances that retain moisture and are applied to these floors to cover the problem but without reaching a true solution. However, over time, the strength as an adhesive barrier of these products decreases and the humidity arises again.
In the case of wood, we find that being a porous material, it will often allow low humidity levels to pass with little or no obvious sign that something is wrong. The result is that these old floors often seem dry and in good condition, when in fact a big problem is brewing.
Moisture
When a wooden look vinyl tile (กระเบื้อง ยาง ลายไม้, which is the term in Thai) is installed on top of an old floor, a very large problem is primarily being covered. Moisture that rises through wood or concrete is trapped under the laminate or vinyl layer. This causes, for example, the wooden boards or parquets to expand and erupt upwards, and so creating a tilt or bulge effect.
In some cases, moisture can affect the laminate floor. This causes the laminate to expand excessively. It usually causes an expensive repair or replacement.
Conclusion
If your floor is old, do not risk installing anything on top. Pick up the parquet, wood or old vinyl, let floor installers provide adequate wet insulation on the concrete.