Should I use plastic sheeting with underfloor heating?
Yes, you should always use plastic sheeting with underfloor heating, regardless of the type of sub-floor and age of the joists. The plastic sheeting protects the floor against the moisture that is always present in joists. When the heating is switched on, the moisture is driven against the surface of the floor by the vapour pressure. Without plastic sheeting, the moisture migrates up into the wear layer of the parquet floor and is trapped under the lacquer pre-finish. This can result in moisture damage.