A comment
When I changed the kitchen I decided to completely replace the floor. One by one it turned out that the floorboard had rotted a lot, and with it a few lags. Masters persuaded to make a bulk floor on expanded clay screed.
We ordered 31 gypsum forman, they said that just what you need for fast work. The layer was made 3 cm thick. Actually the filling itself was done much faster than preparing for it. As builders explained, there is always a lot of liquid in bulk floors and it is necessary that it does not soak into the base and most importantly does not leak to the neighbors from below, otherwise repairs will need to be paid for in two apartments.
To do this, the base must be primed several times, in addition, it is necessary to find and seal the "glass" through which the chandelier is attached with pieces of film. There were times when almost the entire fill flowed through such a hole into the room