Underfloor Heating with Parquet Flooring

Yes, parquet can go in a room with underfloor heating: the two do not exclude each other, provided the covering is chosen for underfloor heating, the sub-floor is dry and level, and during use the floor's surface temperature and the air humidity are watched. We summarise these points based on the advice of Szép Házak Online (a Hungarian home magazine), supplemented with what they mean for heating film underfloor heating.

The professional basis is the building advice "Padlófűtés parketta burkolatnál" (Underfloor heating with parquet flooring) from Szép Házak Online, which we took over in 2016. Below we present it briefly in our own words, and add our own experience.

What does Szép Házak Online advise?

First, the sub-floor has to be checked

Before laying parquet, make sure that the moisture content of the concrete sub-floor is within the parquet manufacturer's specification; this can be measured with a moisture meter. If the concrete is dry enough, the surface must also be smooth, level and dust-free, and any unevenness has to be repaired before laying.

(Photo: Kaindl)

Underlay layers under the parquet

With floating installation, two underlays go under the parquet. The first is a vapour barrier foil, which protects the underside of the wood from residual moisture rising from the concrete. On this goes the impact sound reduction layer, which dampens the tapping sound produced when walking – it is worth choosing a good-quality product here. If the parquet is glued over the full surface, the two underlays are omitted, and in that case a quality PU adhesive is recommended.

(Photo: QuickStep)

Surface temperature and humidity

According to manufacturers' recommendations, the surface of parquet over underfloor heating may be at most 27 °C, and the relative humidity of the air should be kept between 40–60%. This range suits both human comfort and the durability of the wood.

• In air that is too dry the wood shrinks: gaps open between the boards, and the surface can even crack lengthwise. This occurs mostly at the beginning of the heating season, so using a humidifier is recommended then.
• In air that is too humid the parquet absorbs moisture and swells: it can press against the wall at the expansion gap, buckle, and in extreme cases the glue bond tears, or the expanding covering can even damage the concrete.

What does this mean for heating film underfloor heating?

The advice of Szép Házak Online applies primarily to wet-pipe underfloor heating built into concrete, but from the parquet's point of view it also holds for heating film electric underfloor heating: the sub-floor should be dry and level, the floor surface should not overheat, and during the heating season watch the humidity. With both systems, drilling or nailing into the floor should be avoided, because mechanical damage can also damage the heating – so it is worth planning the places of furniture that has to be fixed in advance.

With heating film, the layer structure under the parquet is determined by the type of covering: a reflective foil goes under the film, a vapour barrier foil above it, and depending on the covering, a dry screed or concrete layer may still be needed. The layer structure recommended under laminate parquet is shown on our underfloor heating page. A thermostat with a floor sensor keeps the floor's surface temperature within the limit that suits the covering.

Source: Szép Házak Online (szephazak.hu)