Thin-Screed Underfloor Heating
in Old Buildings – Structure, Costs & Planning

A thin-layer system is a radiant floor heating system with a particularly low installation height – in contrast to classic wet screed (65–80 mm), a total build-up of 17–30 mm is sufficient here. The system consists of a self-adhesive studded foil or a hook-and-loop fleece, PE-RT heating pipes (Ø 12–16 mm), and a fast-curing special screed (Planogel Rheo). It is particularly suitable for old buildings where the existing floor structure is to be preserved and doors or window sills cannot be adapted.

The total build-up is calculated depending on the variant:
Wet System (Dimpled Sheet NP12): 10 mm sheet + 12 mm pipe + 5 mm screed above pipe = 17 mm total
Wet System (Dimpled Sheet NP16): 14 mm sheet + 16 mm pipe + 5 mm screed = 22 mm total
Dry System (ArdusAlu): 22–30 mm without wet screed
For comparison: Traditional wet screed is 65–80 mm. The thin-layer system is the ideal solution if door undercuts are limited or the existing floor is to be preserved.

MC Therm thin-layer system complete sets start at approx. €15/m² for dimpled sheets and heating pipes. The complete set, including dimpled sheets, pipes, edge insulation strips, and connection set, costs €20–35/m² depending on the pipe diameter and spacing. Additionally, there is Planogel Rheo special screed (approx. €30–40/m²). Total material costs, including screed, are typically €50–75/m² – significantly cheaper than a renovation involving breaking up the old floor. → Detailed Cost Overview 2026

Yes – the thin-layer system is well-suited for experienced DIY enthusiasts. The studded mat is self-adhesive, and the heating pipe simply clips in. The most challenging part is the correct application of the Planogel Rheo screed (pay attention to the mixing ratio, ensure uniform thickness). Important: Pressure test (4 bar, 24 h) BEFORE the screed. If you are unsure: MC Therm offers free planning advice including quantity calculation. → Step-by-step installation guide

NerthusFlow Dimpled Sheet: Structured PE film with dimples, into which the heating pipe is directly clipped. Self-adhesive underside - stick directly onto screed or tiles. Variants NP12, NP14, NP16 for pipe diameters 12–16 mm. Installation height: 10–16 mm. No clips required.
MC KLETT Fleece: Flat support fleece with hook-and-loop structure, onto which the pipe is simply pressed. Installation height only 5–6 mm – even flatter than dimpled sheets, ideal when every millimeter counts. Both are compatible with Planogel Rheo or traditional anhydrite screed.

Yes – the thin-layer system and heat pump are the optimal combination. Underfloor heating systems operate with flow temperatures of 30–40 °C, at which heat pumps achieve their best efficiency (COP 4–5). Traditional radiators require 65–75 °C – where heat pumps operate inefficiently (COP 2–3). Those who combine their heat pump with the thin-layer system typically reduce heating costs by 30–50% compared to a gas radiator system.

The 16mm heating pipe is recommended if any of these conditions apply: circuit length over 80 m, room area over 20–25 m² per heating circuit, or in combination with a heat pump. The 16mm pipe has ~30% less pressure loss, allows circuit lengths up to 100 m, and improves the heat pump's COP through more uniform flow.

For the 16mm PE-RT EVOH heating pipe, the NerthusFlow knobbed sheet for 16mm pipe (NP16) is required. The knob geometry is adapted to the pipe diameter. Wet construction height: approx. 22 mm total. The 14mm film does not hold the 16mm pipe securely.