Balcony — three-layer wall — termPIR®

Junction function

A balcony in a three-layer wall is the most challenging thermal detail in a single-family house. The reinforced concrete balcony slab is inserted into the wall (a continuation of the floor slab), creating a major thermal bridge — without insulation, heat losses increase by 10-15% for the whole building.

Full balcony insulation requires three layers of termPIR®:

1. In the wall — termPIR® AL in the 3-layer cavity.
2. Under the balcony — termPIR® ETX (vapour-permeable, ready for render).
3. On the balcony — termPIR® WS/BWS under the screed (vapour-permeable or bituminous).

Together, these three layers “wrap” the RC slab and break the thermal bridge.

Critical installation aspects

• Balcony soffit insulation (item 06) — termPIR® ETX glued to the underside of the slab + mechanically anchored. Finished with mineral render on mesh (item 07). Minimum 80 mm to eliminate the thermal bridge.
• Balcony floor insulation (item 09) — termPIR® WS or BWS laid on the waterproofing (item 08). The BWS glass fleece version is preferred for balconies using torch-on bitumen membrane as waterproofing.
• Slope-forming layer (item 16) — beneath the WS/BWS insulation, 1.5% fall from the wall to the balcony edge. The wedge-shaped board arrangement allows the slope to be adjusted.
• Balcony drip flashing (item 14) — discharges water beyond the façade line. A drip edge (bent-down edge) is required to prevent water running down the wall.
• Balustrade (item 15) — fixed before laying the finish; fixings sealed with silicone (leaks at fasteners are a typical defect).
• Waterproofing (item 08) — double torch-on bitumen membrane in the corner with the wall, 150 mm upstand onto the wall beneath the flashing.

Comparison with an ETICS balcony

Aspect	3-layer (this one)	ETICS
External wall	termPIR® AL in cavity	termPIR® ETX under render
Balcony soffit insulation	termPIR® ETX	termPIR® ETX
Cost per m²	higher (3 layers + cladding)	lower
Façade durability	100+ years (clinker/stone)	30-50 years (render)
Thermal bridge	minimal (3 insulation layers)	minimal

Occurs in the three-layer wall system.

Documentation

termPIR® Catalogue — Residential Buildings (Gór-Stal, 2022), p. 43 — vertical section of a balcony in a 3-layer wall.

Components in this junction