Hi I helped lay click laminate in my daughters lounge which is dipping in 3 or 4 areas when walked on. The house was built around 1940 has a concrete floor with a thin layer of bitumen and then floorboards laid directly ontop. One small section of floorboard approx 18" in the corner of the room had rotted which we replaced and in the doorway a couple of the floorboards were dipped in the middle and raised at the edges. We ensured all the floorboards were secure by nailing down before we started laying the 7mm fibreboard sheets which we though would be better at levelling the surface where needed. (I now realise I omitted to leave the 2mm gaps in between the underlay sheets and only noticed this when re reading the instructions and in some places didnt leave the expansion gaps at the walls as I didn't realise the fibreboard can contract and expand). When watching people walk on the floor it can dip for 2 feet or so around the area trodden on. The flooring was only laid 5 days ago and we are going to lift and start over. I have bought an electric planer to take the edges off the couple of raised floorboards and am wondering if I need to put plyboard or osb board down on top of the floorboards if so what thickness would be required, or can the issue be caused by the underlay being too tight, or as I've been advised by a flooring supplier today maybe I've used the wrong type of underlay? Any advise please, as my daughter is on a budget and cant afford to get a fitter in.