Underfloor Heating Staple System Installation Height: EPS Thickness & DIN 18560

Tacker System Installation Height: EPS Thickness, Screed & DIN 18560 Explained

How high will the floor structure be with the tacker system? The answer depends on three layers: EPS insulation board, pipe diameter, and screed cover. This page explains the formula, shows typical structures ranging from 71 mm to 111 mm, and explains which EPS thickness the GEG prescribes for new construction, basements, and ground floors.

⏱ 10 min. read

Standard-compliant according to DIN 18560 & GEG

Calculation examples for 4 setups

What you need for the calculation

Materials with an impact on the assembly height

→EPS Folded Slab WLG 040, 30 mm (standard new build above basement)
→EPS folding panel WLG 035, 25 mm (for limited installation heights)
→PE-RT heating pipe 16×2 mm (pipe diameter is included in the calculation)
→Cement screed CT (minimum cover 45 mm over pipe)
→Edge insulation strips (height = EPS + pipe diameter + screed + covering)

Prerequisites for Planning

→Known clear room height — Installation height must not be lower than door frame
→Type of use clarified: residential, commercial, bathroom — affects compressive strength of the EPS board
→Building physics requirement known: New construction over basement/ground requires R ≥ 1.25 m²K/W
→DIN EN 1264 and DIN 18560 considered as basis for standards

Understanding Installation Height: Formula & Standard Basis

The total installation height of the tacker system is calculated using the simple formula: EPS thickness + pipe diameter + screed covering. All three values are influenced by standards: The EPS thickness by the GEG (minimum R-value), the pipe diameter by planning (standard: 16 mm PE-RT), the screed covering by DIN 18560 (at least 45 mm CT above the pipe). This results in a minimum of 86 mm for EPS WLG 035 with 25 mm — and typical installation heights of 91–111 mm in new builds.

Calculate the installation height: 6 steps

Step 1: Formula & Basic Principle: The total height of the tacker system consists of three layers: EPS thickness + pipe diameter + screed cover over the pipe. Formula: H_total = EPS + D_pipe + cover. Example: 30 mm EPS + 16 mm pipe + 45 mm screed = 91 mm total height. In addition, there is the grid foil (approx. 0.5 mm, negligible) and the floor covering (tiles, parquet, etc.).

Step 2: EPS Thickness according to GEG and DIN EN 1264: The EPS thickness is determined by the building physics requirements, not by the installation height alone. For new buildings above unheated basements or the ground, the following applies: R ≥ 1.25 m²K/W (thermal resistance of the insulation layer). For EPS WLG 040 (λ = 0.040 W/mK), this corresponds to a minimum thickness of 50 mm (R = 50/0.040 = 1.25). For EPS WLG 035 (λ = 0.035), 44 mm is sufficient for the same R-value. For areas above heated basements, R ≥ 0.75 m²K/W is sufficient — i.e., approx. 30 mm EPS WLG 040.

Step 3: Minimum screed cover according to DIN 18560: The screed cover over the pipe is normatively defined. For cement screed (CT), at least 45 mm above the pipe crown applies. For anhydrite screed (CA), at least 30 mm is permissible. For increased surface loads (> 3 kN/m², e.g., commercial use), at least 55 mm. The total screed height (pipe + cover) is then calculated as: 16 mm pipe + 45 mm = 61 mm screed above the pipe underside, or 16 mm + 45 mm = underside of EPS to top of screed: 30 mm EPS + 16 mm pipe + 45 mm = 91 mm total.

Step 4: Example calculations for typical setups: Structure 1 (New build, heated basement, standard): EPS WLG 040, 30 mm + 16 mm pipe + 45 mm screed = 91 mm. Structure 2 (New build, above ground, GEG compliant): EPS WLG 040, 50 mm + 16 mm pipe + 45 mm screed = 111 mm. Structure 3 (limited height, renovation): EPS WLG 035, 25 mm + 16 mm pipe + 45 mm screed = 86 mm minimum. Structure 4 (Anhydrite, very limited): EPS WLG 035, 25 mm + 16 mm pipe + 30 mm CA = 71 mm.

Step 5: Heating output and EPS thickness: The EPS thickness affects not only the structural height but also the heating output. A thinner EPS board with a lower R-value allows more heat to radiate downwards – which reduces efficiency. Example: With 25 mm EPS WLG 040 (R = 0.625), approximately 20–25% more heat is lost downwards than with 50 mm EPS (R = 1.25). For maximum upward heating output (approx. 70–90 W/m² at 15 cm spacing, 40 °C flow temperature, 30 mm EPS), the upward R-value is limited by the screed and floor covering.

Step 6: Edge insulation strips and expansion joints: The perimeter insulation strip must cover the entire floor structure, including the floor covering: EPS + pipe diameter + screed + covering thickness. For a 91 mm structure and 10 mm tile, this means a strip height of at least 101 mm. Expansion joints are mandatory according to DIN 18560 for areas over 40 m² or sides over 8 m. In L- or T-shaped rooms, always provide an expansion joint at the constriction.

Frequent questions about the Tacker system's installation height

The absolute minimum installation height is 86 mm: EPS WLG 035 at 25 mm + 16 mm pipe + 45 mm cement screed (CT). With anhydrite screed (CA, 30 mm minimum covering), 71 mm is theoretically possible, but CA screed is more expensive and more sensitive to moisture.

For new buildings above unheated basements or ground, the GEG (German Buildings Energy Act) specifies a thermal resistance R ≥ 1.25 m²K/W. With EPS WLG 040 (λ = 0.040), this means at least 50 mm. With EPS WLG 035 (λ = 0.035), 44 mm are theoretically sufficient — practically, 45 or 50 mm are recommended.

According to DIN 18560, cement screed (CT) must be at least 45 mm above the pipe crown. For anhydrite screed (CA), it must be at least 30 mm. For increased surface loads (commercial, > 3 kN/m²), CT must be at least 55 mm. These values are minimums — exceeding them does not violate the standard but increases the overall height.

Yes. For the same target R-value (R = 1.25 m²K/W), thermal conductivity group (WLG) 035 only requires 44 mm instead of 50 mm for WLG 040 — saving 6 mm in overall thickness. For a lower target R-value (above a heated basement, R = 0.75), WLG 035 already suffices with 26 mm instead of 30 mm. However, EPS WLG 035 costs approximately 40% more than WLG 040.

Yes, for the clear room height, the entire construction height from the underside of the structural floor to the top of the finished floor counts: EPS + pipe + screed + adhesive/impact sound insulation + covering. A 10 mm tile with 5 mm adhesive is added to the 91 mm structure – total height then 106 mm. Door heights and door frames must take this into account.

For residential spaces, EPS WLG 040 with 5,000 kPa compressive strength is sufficient. For commercial use (> 3 kN/m²), EPS WLG 035 with 10,000 kPa is recommended. EPS WLG 045 with 4,000 kPa is adequate for light loads (residential, max. 2 kN/m²). The compressive strength must permanently withstand the load from the screed + usage.

The following are decisive: DIN EN 1264 (Underfloor heating, system requirements), DIN 18560 (Screed work in construction, screed thicknesses), DIN 4109 (Sound insulation), GEG (Building Energy Act, insulation thicknesses) and DIN 18202 (Tolerances for subfloor flatness). Compliance with these standards is mandatory when planning by specialist companies.