Hi... would greatly appreciate any input/ insight from this forum. I am new home owner (of a 50 year house) and decided to rip out the existing carpet and put in pre-finished engineered floors in the family/ living rooms of the house. Unfortunately, as the contractor ripped out the carpet he saw that the floor was uneven and covered with vinyl tiles. He recommended ripping off tiles and laying self-leveling cement before glueing down the engg. wood.

Unfortunately 2 days after installing the self-leveling cement it does not seem to have adhesion with the sub-floor for ~75% of the floor-area (and is basically floating over the ground/ concrete). Mysteriously, its got got strong adhesion in patches of the floor. Has anyone seen something like this before? What could have been the cause/ what can we do to prevent it again? Also, given this adhesion problem is it better to "float" vs "glue-down" the engineered floor? Thanks much for any help!