hi all,
just picked up a job at last lol and the guy wants to keep is floor height to a min, currently the bathroom floor is 18 or 21mm tongue and grove chip board sheets in a new build (2004) all screwed down at 300mm centres and all joints on joists, the floor size is 1.50m x 2.50m i said i would need to put 15mm ply on top, prime, flexy adhesive and tile (ceramic 300x300) raising is floor about 23mm ish, not what he is looking for has his carpet sits at 10mm ish on the landing and he wants to keep the raise to a min so there is very little difference in height, have explained there are some very good carpet to tile trim which will give the appaerence of the floors being of similar in height....anyone got any other idea's to keep the height profile to a min or would do it differently...cheers for any help or advice, Beau...
PS he is not to concerned about the floor being 100% waterproof

With a floor that small and if it is the thicker chipboard, you may well get away with just using Ardex-flex 7001 straight down on the floor. This is dependent on the floor being solid. At the same time for a bit of extra insurance you could lay 6mm Hardiebacker or No More Ply and tile onto that.