New floor not level - dipping

[broburus]

I have a wooden chipboard floor resting on insulation (1/2 inch solid board foamy stuff (seltex?) on a concrete slab.

Unfortunately the floor was layed on an uneven concrete base (used to be a garage)

If i put a length of timber from wall to wall the gap slope/dip at the centre is about 1& 1/2 to 2 inches.

I am putting laminate flooring in so need to get it level.

Not sure wether to try and create a level floor by using hard board 1 inch thick in the middle then going to 1/2 inch going to 1/4inch ?! or can i use extra think underlay in the middle (or double it up) and thinner on the outside edges.

Any suggestions ?

[gcol]

You should add concrete to roughly level the floor - use said piece of timber to screed it flat. Then use self leveling compound. Then lay your DPM, underlay and laminate.