X marks the spot

I assessed the floor levels yesterday and using the laminate floor underlay cut into small pieces I managed to work out how many layers would be needed at various points over the whole floor to get every bit of the surface completely level. 

The variation is huge:

- X near the bottom of the image marks the highest point in the room 

- Other X's near the back mark pivot points

- Green blobs mark the height required to level to that point

- thin blue strands mark dips below the visible surface

- raise by 13 layers at most (x 2mm underlay) needs uplifting by 26mm

- Height shifts are inconsistent, undulating rather than sloping

Questions: 

- can the flooring be lifted and reused

- has glue been used anywhere underneath 

- what else is under the laminate - other packing

- chart the layers 

- do we have to go back to the concrete?