I've had a new room built with an 18mm weyroc moisture resistant chipboard floor screwed down. I'm looking to fit a karndean floor and the fittinmg instructions say I need to put down a 6mm ply floor first. Has anyone layed a karndean floor directly onto a chipboard floor without the ply? The floor is very stable with not much movement at all. I can see that sheets of 8x4 ply will provide less joins but it's obviously an extra cost.