check this out http://www.insulation.kingspan.com/newdiv/pdf/tf73.pdf I was thinking of using this as replacement floor in my bathroom and tile over it. It is a normal joist and board floor. I want to get rid of the bath and install a stone resin shower tray. Problem is, the TF73 stuff is chipboard but Kingspan say this : ABSORPTION OF MOISTURE Kingspan Thermafloor TF73 zero ODP is not sensitive to moisture of any kind. Its surface is water–repellent and there is no capillary suction. The material is also not hygroscopic. Over a 28 day cycle with temperature fluctuating 20/40°C its water absorption is <0.5% when tested to BS 3837: Part 2: 1990 (1996) (Specification for extruded boards). 1. Will it be strong enough to support the tray and stop movement? 2. Will it be OK in a bathroom environment? Discuss.