Ground floor slab (termPIR® AL)

Junction function

Ground floor slab = standard for 90% of new single-family homes in Poland (vs basements 5%, suspended floors 5%). Build-up from bottom:

1. Native soil (item 07) — roller-compacted; if weak (peat, clay) replaced with sand.
2. Gravel bedding (item 06) — 20–30 cm of gravel, 4–16 mm grading; capillary water drainage + load-bearing base.
3. Concrete slab (item 05) — typically 12–20 cm of reinforced concrete with mesh; structural load capacity.
4. PE film (item 04) — vapour barrier against water vapour rising from the ground.
5. termPIR® AL (item 03) — typically 10–15 cm; thermal insulation.
6. Cement screed (item 02) — 4–6 cm screed.
7. Floor finish (item 01) — final layer.

Critical installation aspects

• PE film (item 04) — MANDATORY; capillary rise of water vapour from the ground = insulation degradation without film. Minimum thickness 0.15 mm, overlap 20 cm, sealed with vapour-tight tape.
• termPIR® AL (item 03) — typically 10 cm for WT 2021 (U ≤ 0.30 for floors); for passive houses 15–20 cm; 2 layers with 3 mm expansion gap for thicknesses >12 cm.
• At walls — 10 mm EPS expansion strip around the entire perimeter; without it the rigid floor-to-wall connection = linear cracks.
• Screed (item 02) — reinforced with steel ladder mesh or polypropylene fibres; without reinforcement it cracks after the first winter. Thickness min. 4 cm, min. 6 cm for underfloor heating.
• Gravel bedding (item 06) — 4–16 mm grading (NOT fine sand which clogs quickly); compacted in 10 cm layers; geotextile under the gravel is optional (prevents mixing of soil with gravel).
• Waterproofing at floor level (level +/- 30 cm relative to ground) — SBS bitumen membrane 5 mm on the concrete slab, continued with a 30 cm overlap onto the walls; protects walls from capillary rise of water from the ground.

Documentation

Technical Catalogue termPIR® — Residential Buildings (Gór-Stal 2022), page 64 — Floors and slabs, insulation detail for ground slab and floor on ground. Scale 1:10.

Components in this junction