Advise needed on laminate flooring

[cowoman]

Hello,we need to cover our floorboards on the upstairs landing with laminate flooring.The problem we have is that the boards go vertical down the hallway and then where the wall has been knocked through the boards go horizontal across the hallway.

From the begginning to the end there is an uneveness.A builder friend said to take up the difference with the thick underlay.I think he meant adding more layers in the lower areas to take up the level.I have been looking on the net and it says to put hardboard over boards first.I need some advise.

One thing do they sell hardboard in France?I cant say that I have noticed it and how do we go about getting this floor suitable to lay the laminate on it?

If theres anyone on here who can help with advise I would really appreciate it.I can post a photo if it might give more of an idea whats what but i dont think the levels will show on it

Thanks in advance

[cooperlola]

I used that green stuff which comes in large squares for this.  Can't remember what it's called but I can probably find it somewhere.

[cowoman]

so did you put double layers where neccasary to take up the levels?

[cooperlola]

You can use double layers where you have a difference in levels, but my personal experience is that it isn't easy to get this right!  A number of these products (some of which provide sound-proofing also) are in the Point P catalogue

http://www.pointp.fr/pages/catalogues_inter/pointp/2008/carrelages_parquets/appli.htm