Retrofitting underfloor heating in an old building using dry construction – without wet screed

Q: Is the dry construction system the best solution for underfloor heating in old buildings?

For old buildings with wooden beam ceilings: yes – the only sensible solution, as wet screed is too heavy (100–120 kg/m²) and would cause permanent deflection of the wooden beams. For old buildings with solid ceilings and sufficient build-up height: tacker system is more economical (from €8/m²). For minimal build-up height under 40 mm: check thin-layer system. The correct choice primarily depends on the subfloor type, build-up height, and sound insulation requirements.

Q: How much lighter is the dry lining system compared to wet screed?

Drywall system (system panels + dry screed): 25–37 kg/m². Wet screed (cement screed 65 mm): 100–120 kg/m². The drywall system is 3–5× lighter. For 50 m², this means a weight saving of 3,150–4,150 kg—critical for old wooden beam ceilings with limited load-bearing capacity.

Q: When is wood fiber insulation board worth it instead of EPS 300 in old buildings?

Wood fiber system panel (€22.64/m²) is worthwhile for: timber beam ceilings (integrated impact sound insulation up to 56 dB), multi-family homes with DIN 4109 requirements, ecological building projects. EPS 300 (€14.92/m²) is sufficient for: single-family homes on concrete, where no sound insulation is required. Price difference: €7.72/m², for 50 m² = €386 additional cost for integrated sound insulation.

Q: How long does the dry-screed underfloor heating installation take in an old building for 50 m²?

Net working time for 50 m²: Subfloor + insulation: 2–3 h. Bonding system panels: 3–4 h. Laying pipes + connection: 3–4 h. Leak test: 24 h waiting time. Dry screed: 3–4 h. Walkable after another 24–72 h. Wet screed comparison: Screed installation + 7–21 days drying time. Time saving compared to wet screed: 7–21 days — crucial for occupied old buildings.

Q: Does the drywall system work with my old heat pump?

Yes — the drywall system is fully heat pump compatible (flow temperature 30–45 °C). In existing buildings, a higher surface heating capacity requirement is often needed: choose a narrower pipe spacing (150 mm instead of 200 mm) and ensure sufficient thermal insulation. Have a hydraulic balance carried out by a specialist company. A flow temperature of 45 °C is sufficient for well-renovated older buildings (U-value exterior wall ≤ 0.35 W/m²K).

Q: What is the cost of the drywall system in an old building for 100 m²?

Material costs for 100 m² (EPS 300 variant without dry screed): System panels €14.92/m² = €1,492, heat conducting plates 4.5 × €1.77 × 100 = €797, pipe 7 m/m² × €0.70 × 100 = €490, edge insulation strips approx. €127. Total approx. €2,906. Plus dry screed approx. €1,300 = total approx. €4,206. Plus installation labor by specialist company €20–35/m² = €2,000–3,500. Total costs approx. €6,200–7,700.

Underfloor heating retrofit in old buildings without wet screed — Dry construction system

Retrofitting underfloor heating in old buildings is possible—with the right system. The dry construction system with EPS or wood fiber system panels is the ideal choice for old buildings, timber beam ceilings, and renovations of occupied properties: no wet screed, no screed layer, walkable after 24–72 hours. This guide shows when dry construction is the best solution, how EPS 300 and wood fiber compare in old buildings, and how installation proceeds in 6 steps.

⏱ 9 min. read

Old Building Guide

Without wet screed

When is a drywall system the best choice in an old building?

Ideal Applications in Old Buildings

→Timber beam ceiling: wet screed not statically possible → drywall system mandatory
→Occupied Renovation: Dry screed can be walked on after 24–72 h, no waiting for screed to dry
→Half-timbered construction / listed building: no moisture ingress, no wet screed necessary
→Loft conversion: System weight 25–37 kg/m² instead of 100–120 kg/m² (wet screed)
→Old building with heat pump: Flow temperature 30–45 °C, no high-temperature boiler required

When wet screed systems are a better fit

→Old building on concrete slab with sufficient installation height: Staple system cheaper (from €8/m² material)
→Very low installation height (< 40 mm): Check thin-layer system with heat conductive plates
→New build project with unlimited installation height: Wet screed tacker more economical

Dry Screed vs. Wet Screed in Old Buildings: The Decisive Comparison

In old buildings, timber beam ceilings, limited floor height, and renovations in occupied dwellings present typical challenges. Wet screed is often not an option in these situations: too heavy (100–120 kg/m²) for timber beams, too long a drying time (7–21 days) in occupied buildings, too much construction moisture for listed buildings. The dry construction system solves all three: weight 25–37 kg/m², walkable after 24–72 h, no construction moisture. Dry screed installation time: 0–24 h until walkable. Wet screed: 7–21 days drying time. Dry weight: 25–37 kg/m². Wet screed: 100–120 kg/m². Heat storage dry: low (fast response). Wet screed: very high (sluggish control).

Renovating Old Buildings with Drywall Systems: 6 Steps

Step 1: Analyze the subsurface and structural integrity: Timber beam ceiling: Measure beam spacing, check deflection (max. L/300). Screw down all floorboards firmly, replace loose boards. Measure wood moisture: ≤ 15% (use a moisture meter). Concrete subfloor: Check flatness according to DIN 18202 (max. 5 mm/2 m for drywall construction). Static load capacity: Drywall system weighs 25–37 kg/m² — typically uncritical for timber beams designed for 150–200 kg/m².

Step 2: Choose System Variant: EPS 300 System Panel (€14.92/m²): Standard for concrete floors and solid ceilings, lightweight (0.5 kg/m²), λ = 0.032 W/mK, compressive strength 300 kPa. Wood Fiber System Panel (€22.64/m²): ideal for timber beam ceilings – integrated impact sound insulation up to 56 dB, compressive strength 140 kPa (sufficient for normal residential loads), ecologically sustainable. In multi-family dwellings with sound insulation requirements (DIN 4109), always choose wood fiber.

Step 3: Plan the installation height: Total installation height of the dry construction system: Thermal insulation (e.g., 40 mm EPS DEO) + system panel 25 mm + dry screed element 25 mm = from 90 mm. If installation height is limited: Reduce insulation thickness (observe minimum R-value), rework door frames if necessary. Install perimeter insulation strips: min. 5 mm, height up to top edge of finished floor. Check doors and frames for new floor height—shorten if necessary.

Step 4: Laying system plates and pipes: Lay thermal insulation (EPS DEO ≥ 100 kPa), apply PE film (0.2 mm) if there is a risk of moisture. Glue system plates with flexible adhesive, staggered bond (joint offset min. 200 mm). Insert heat conducting plates (4.5 pcs./m² at 150 mm spacing). Insert PE-RT-ALU-PERT composite pipe 16×2 mm into the channels. Max. pipe length per heating circuit: 90–100 m. Leak test: 6 bar, 24 hours, document.

Step 5: Laying the dry screed: Lay PE separating foil. Lay and glue Fermacell 2E22 elements (2x12.5 mm), with joints offset by at least 200 mm, 10 screws/m². Mark the pipe position before screwing — critical! Walkable within 24–72 h. No waiting for screed drying (wet screed: 7–21 days drying time). For inhabited old buildings: Work room by room, install transition profiles to the inhabited area.

Step 6: Initial setup: Heating Protocol according to DIN EN 1264-4: Start 25 °C flow temperature, increase daily by +5 °C. Old building heat pump: Flow temperature 30–45 °C sufficient for low-temperature radiant heating. Perform hydraulic balancing — old building renovations often have multiple heating circuits with different pipe lengths. Retain protocol. Apply floor covering: all coverings with a max. thermal resistance of 0.15 m²K/W are suitable.

FAQs: Drywall Systems in Old Buildings

For old buildings with wooden beam ceilings: yes – the only sensible solution, as wet screed is too heavy (100–120 kg/m²) and would cause permanent deflection of the wooden beams. For old buildings with solid ceilings and sufficient build-up height: tacker system is more economical (from €8/m²). For minimal build-up height under 40 mm: check thin-layer system. The correct choice primarily depends on the subfloor type, build-up height, and sound insulation requirements.

Drywall system (system panels + dry screed): 25–37 kg/m². Wet screed (cement screed 65 mm): 100–120 kg/m². The drywall system is 3–5× lighter. For 50 m², this means a weight saving of 3,150–4,150 kg—critical for old wooden beam ceilings with limited load-bearing capacity.

Wood fiber system panel (€22.64/m²) is worthwhile for: timber beam ceilings (integrated impact sound insulation up to 56 dB), multi-family homes with DIN 4109 requirements, ecological building projects. EPS 300 (€14.92/m²) is sufficient for: single-family homes on concrete, where no sound insulation is required. Price difference: €7.72/m², for 50 m² = €386 additional cost for integrated sound insulation.

Net working time for 50 m²: Subfloor + insulation: 2–3 h. Bonding system panels: 3–4 h. Laying pipes + connection: 3–4 h. Leak test: 24 h waiting time. Dry screed: 3–4 h. Walkable after another 24–72 h. Wet screed comparison: Screed installation + 7–21 days drying time. Time saving compared to wet screed: 7–21 days — crucial for occupied old buildings.

Yes — the drywall system is fully heat pump compatible (flow temperature 30–45 °C). In existing buildings, a higher surface heating capacity requirement is often needed: choose a narrower pipe spacing (150 mm instead of 200 mm) and ensure sufficient thermal insulation. Have a hydraulic balance carried out by a specialist company. A flow temperature of 45 °C is sufficient for well-renovated older buildings (U-value exterior wall ≤ 0.35 W/m²K).

Material costs for 100 m² (EPS 300 variant without dry screed): System panels €14.92/m² = €1,492, heat conducting plates 4.5 × €1.77 × 100 = €797, pipe 7 m/m² × €0.70 × 100 = €490, edge insulation strips approx. €127. Total approx. €2,906. Plus dry screed approx. €1,300 = total approx. €4,206. Plus installation labor by specialist company €20–35/m² = €2,000–3,500. Total costs approx. €6,200–7,700.

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