Junction function
The plinth of a 3-layer basement wall is the most complete detail in the construction of a heated basement. Four elements of the building meet here:
- 3-layer basement wall — load-bearing leaf + termPIR® in the cavity + outer leaf,
- Basement floor — multi-layer with termPIR® beneath the screed,
- Strip foundation — with a horizontal DPC interrupting capillary rise,
- Above-ground plinth zone — façade finishing at ground level.
A premium variant compared with the two-layer one — the termPIR® insulation is in the cavity between two leaves, protected on both sides against mechanical damage and water. Used in residences with a usable basement.
Critical installation aspects
- Wall tie (item 05) — A2 stainless steel anchors (typically 6 mm × 200 mm), 4 pcs/m². Galvanised black steel is inappropriate — long-term corrosion even in a dry cavity.
- Light-type waterproofing (item 08) — 2-component bituminous compound on the outer surface of the outer leaf. Total thickness ≥ 3 mm after drying. To be used ONLY in the absence of permanent groundwater pressure.
- Horizontal damp-proof course (item 11) — heat-welded bitumen membrane or PE foil on the strip foundation, extending 30 cm in both directions (to the basement wall + to the floor). Eliminates capillary rise.
- Perimeter drainage (item 10) — PVC pipe Ø100 mm in a gravel bed, gradient 0.5-1% to the inspection chamber. Without drainage, accumulated water forces its way into the insulation regardless of waterproofing quality.
- Dimpled foundation membrane (item 09) — dimples facing away from the insulation (gravity drainage), upper edge fixed with a profile to the outer leaf.
- Two-layer floor thermal insulation (items 13, 14) — typically termPIR® AGRO P-REV at the bottom (aluminium facing the ground, resistant to screed alkalis) + termPIR® AL on top, staggered layout to eliminate thermal bridges at joints.
- Above-ground plinth zone (item 18) — transition to termPIR® ETX ETICS or mosaic plinth render with reinforcing mesh.
Used in the 3-layer foundation + floor on the ground systems.
Documentation
termPIR® Catalogue — Residential Buildings (Gór-Stal, 2022), p. 48 — complete cross-section of a 3-layer basement wall with description of 18 layers.
Components in this junction
Insulation (4)
- 03 Wall thermal insulation — termPIR® AL
- 08 Bituminous insulating compound (coating waterproofing)
- 13 Floor thermal insulation — termPIR® AL / AGRO P-REV
- 14 Floor thermal insulation — second layer
Fastener (1)
- 05 Wall tie (stainless steel anchor)
Element (13)
- 01 Strip foundation
- 02 Basement wall — load-bearing leaf (concrete, blocks)
- 04 Basement wall — outer leaf
- 06 Cement render
- 07 Cement-lime render
- 09 Dimpled foundation membrane
- 10 Perimeter drainage Ø100 mm
- 11 Horizontal damp-proof course
- 12 Lean concrete
- 15 Cement screed
- 16 Finished floor
- 17 Reinforced concrete ring beam + slab over basement
- 18 Plinth finishing layer — mesh + decorative render