Pitched roof — under-rafter + between-rafter system W2 (section)

Junction function

System W2 is a variant of W1 with an under-rafter composite termPIR® AL GK panel replacing the separate insulation layer + separate plasterboard. The AL GK panel has 12.5 mm plasterboard factory-laminated to the AL facing — in a single installation step you obtain:

• a PIR insulation layer (typically 50–80 mm),
• a finish layer in the form of 12.5 mm plasterboard, ready for jointing.

Advantages vs W1 (separate insulation + separate plasterboard):

• Reduced structure thickness by 1–2 cm (no technological gap between PIR and plasterboard).
• Faster installation — one layer instead of two.
• Better vapour-barrier continuity — AL facing beneath the plasterboard.

Disadvantages: higher unit cost (the composite panel is approx. 25% more expensive than the sum of termPIR® AL + plasterboard).

Critical installation aspects

• Between-rafter thermal insulation (item 06) — identical to W1; fill gaps with installation foam.
• termPIR® AL GK panel (item 07) — install with a 3 mm expansion gap between panels; joint the gaps like typical plasterboard seams (tape + filler).
• Sub-structure (item 08) — 60×40 mm timber battens at 40–60 cm spacing (depending on AL GK panel thickness); fix to the rafters, NOT to the between-rafter panel.
• Wood screws (item 09) — driven through the batten and AL GK panel into the rafter; length = package thickness + min. 60 mm penetration into the timber.
• Panel laying direction — short edge parallel to the rafters (where possible); cross-joints on the battens (NOT between battens).
• Joint filling — Knauf Uniflott / Rigips Vario filler, paper tape or self-adhesive fibreglass mesh; applied directly to the factory plasterboard — no priming required (the plasterboard is ready for finishing work).

Occurs in the system pitched roof — termPIR® under-rafter.

Documentation

Technical Catalogue termPIR® — Residential Buildings (Gór-Stal 2022), page 25 — Pitched roof, system W II, roof section. Scale 1:10.

Components in this junction