It is a popular egg plate.
So that the moisture on the foundation surface does not affect the basement floor
It is a floating material.
The official name is moisture-proof pallet.
It removed a lot of moisture from the underground parking lot in a detached house.
By the way
In fact, even a house built on the ground floor
It is good if this goes in.
However, the cost of this material is not expensive, but the cost of installation labor, raw concrete material, and labor costs are more expensive, so general owners do not use it.
We have to spend even if it is expensive.
This is because it is the basic of being freed from the dampness of the ground.
So you have to write it if you need it.