Hi, I am looking at buying 40m2 of click oak flooring but just need a bit of advice about laying it. I am laying it over a floor that is half concrete which then meets a chipboard floor (suspended timber floor), there was a dividing wall there that has now been removed. The joint is pretty good within 2-3mm, the chipboard floor is nice and flat. I am just a bit concerned about the concrete side, it is a rough poured concrete and where walls have now been removed the levels aren’t perfect and there are dips and rises that I have noticed. I just wanted to know what the tolerance is like on the flatness of a sub layer before laying click flooring? I am guessing it is worth trying to get it as flat as possible, are there any tricks/products for achieving this? (The underlay helps abit aswell I am told?) I dont think that using self levelling concrete to get the whole floor level and flat would be worthwhile?!(disruption and hassle? never used it before, we are living in the house and need access through the room). I did wornder about mixing some sharp sand and cement for the dips and fading it at the edges so there is no big steps? I guess I am hoping that a gently undulating floor that is not dead level or flat will be ok? Obviously, a totally flat concrete floor would be ideal, but.....I have found 'ideal' rarely happens during renovations!! The last thing I want is a floor that bounces or squeaks etc. Advice from people who have experience would be appreciated. Many thanks, Dan.