Two-layer basement wall (termPIR® WS + AL floor)

Junction function

Full basement of a single-family house — basement wall 240 cm high, insulated externally with termPIR® WS + basement floor insulated with termPIR® AL. Two different materials for different conditions:

• Basement wall = termPIR® WS — water-resistant (W2L class), withstands 28-day moisture contact, bonded to bitumen.
• Basement floor = termPIR® AL — classic sub-floor insulation; AL facing upwards (vapour tightness), beneath the screed.

Light-type waterproofing = conditions with a low groundwater level (>50 cm below foundation level). For high groundwater level → heavy type (2-layer bituminous membrane + bottom drainage + even water pumps).

Critical installation aspects

• Layer hierarchy — from basement interior outwards: floor finish → screed → AL → lean concrete → soil; from the basement wall side: cement-lime plaster → basement wall → external cement plaster → bitumen → WS → dimpled membrane → soil.
• Horizontal damp-proof course (item 02) — SBS bituminous felt 5 mm AT foundation level; overlaps minimum 10 cm; continued ABOVE GRADE on the above-ground wall (capillary rise from basement to ground floor = classic mistake).
• termPIR® WS bonded to bitumen (items 06+07) — 2-layer bitumen application is essential (Botament BE 901 or Bibrol BIT-IN), total thickness 2.5 mm, full-surface bonding.
• Perimeter drainage (item 09) — required for every basement; perforated DN 100 pipe, 30 cm gravel bedding, geotextile; 1% slope to inspection chamber.
• Basement floor — beneath the screed 2 layers of termPIR® AL laid with offset joints (with 3 mm gap between boards for thermal movement); vapour barrier on the screed side.
• Basement ventilation — minimum gravity mechanical (ventilation stack from the roof) or heat recovery system; without ventilation = condensation moisture in the basement despite good insulation.

Documentation

Technical Catalogue termPIR® — Residential Buildings (Gór-Stal 2022), page 44 — Two-layer basement wall (light-type waterproofing). Scale 1:10.

Components in this junction