Repair Systems — 03 — Facade & External Envelope
Vapour-Permeable Wall Wrap / Sarking
Technical product reference for vapour-permeable wall wrap and sarking products installed in the drained cavity behind facade cladding systems — breather membranes, drainage mats, and self-adhesive house wraps that shed water penetrating the outer cladding layer to the drainage cavity while allowing vapour to pass outward. Required under NCC 2022 for most external wall cladding systems.
What are vapour-permeable wall wrap and sarking systems?
Wall wraps and sarking are the second line of defence in a rainscreen cladding system — installed directly over the structural framing or sheathing, behind the subframe and cladding panels. They prevent any water that passes through the outer cladding from reaching the primary structure, while also controlling vapour movement through the wall assembly.
Product Reference
4 product systems — wall wrap and sarking — scroll to view all
Ametalin ThermaWall Vapour-Permeable Wall Wrap
Vapour-permeable wall wrap — Class A breather membrane
System Description
Ametalin ThermaWall is a vapour-permeable wall wrap (breather membrane) installed directly over the structural sheathing or stud wall before the cladding subframe and panels are installed. The membrane allows water vapour generated inside the building to pass outward through the wall (preventing interstitial condensation), while blocking liquid water driven inward by rain from reaching the primary structure. Class A per AS 4200.1 — UV stable for up to 6 months prior to cladding installation. The key distinction from vapour barriers: ThermaWall allows vapour to pass (Sd < 0.1 m) — it does not trap moisture inside the wall. Laps and penetrations must be sealed with compatible self-adhesive tape.
Technical Properties
- Type: vapour-permeable breather membrane — Class A per AS 4200.1
- Sd value: < 0.1 m — high vapour permeance — allows interstitial drying
- Water entry pressure: > 500 mm water column — resists liquid water ingress
Limitations
- Must not be used as a vapour barrier — it is permeable and will not prevent vapour ingress
- UV exposure limited to 6 months — must be covered by cladding within this period
- Laps and penetrations must be sealed with compatible self-adhesive tape — unsealed laps allow water ingress
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Kingspan Kooltherm W1 Reflective Vapour Barrier
Reflective foil vapour barrier — Class B — NCC 2022 Section J
System Description
Kingspan Kooltherm W1 reflective foil provides both a vapour barrier (Class B per AS 4200.1 — low vapour permeance, Sd > 20 m) and a radiant heat barrier in wall cavities. The reflective foil surface reflects radiant heat back into the building in winter and reflects incoming solar radiant heat in summer — contributing to NCC 2022 Section J thermal performance compliance. Unlike vapour-permeable membranes, Class B foil barriers have high resistance to vapour passage — they are used where it is specifically required to prevent moisture vapour moving from a high-humidity interior. A minimum 25 mm air gap must be maintained between the reflective surface and the adjacent material for the thermal barrier function to operate.
Technical Properties
- Type: reflective foil vapour barrier — Class B per AS 4200.1
- Sd value: > 20 m — high vapour resistance — blocks vapour movement
- Emissivity: ε < 0.05 — highly reflective — contributes to Section J Rf value
Limitations
- Class B vapour barrier must only be used where vapour control is the design intent — use Class A in most cladding
- Traps moisture if installed incorrectly — consult building physicist for climate zone analysis before specifying
- Reflective surfaces require 25 mm air gap to function as radiant thermal barrier
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
Pro Clima SOLITEX EXTASANA Premium Facade Membrane
Premium vapour-permeable facade membrane — airtight laps — passive house
System Description
Pro Clima SOLITEX EXTASANA is a premium German-engineered vapour-permeable facade membrane (Sd < 0.02 m — ultra-high permeance) with an airtight lap tape system for use in high-performance building envelopes. Where standard wall wraps rely on overlapped laps for watertightness, the EXTASANA system uses a compatible self-adhesive Tescon tape to create airtight joints between sheet runs — contributing to the building's air leakage performance (NCC 2022 requires < 10 m³/h/m² at 50 Pa for Class 2 buildings). The 12-month UV exposure rating (versus 3–6 months for standard wraps) provides greater construction programme flexibility.
Technical Properties
- Type: vapour-permeable facade membrane — Class A per AS 4200.1
- Sd value: < 0.02 m — ultra-high permeance — passive house and NCC 2022 compatible
- Airtight lap tape: Tescon Vana — site-applied — creates airtight joint at laps
Limitations
- Higher cost than standard wall wraps — justify in high-performance envelopes only
- Airtight tape system requires trained installer — not suitable for general labour
- Specialist importer — lead times can be 4–8 weeks — include in programme
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
CSR Sisalation 450 Reflective Wall Sarking
Reflective wall sarking — Class B — standard residential
System Description
CSR Bradford Sisalation 450 is the most widely used reflective wall sarking in Australian residential construction — a low-cost foil/kraft laminate wall wrap installed behind timber-framed cladding. Class B per AS 4200.1 — acts as both a vapour barrier and a radiant heat reflector. Used behind Colorbond Walling, FC sheet, and timber weatherboard cladding in standard residential construction. For NCC 2022 Section J compliance contribution, a 25 mm air gap must be maintained between the reflective surface and the adjacent material. Laps are stapled — not airtight — not suitable for airtight building envelope targets.
Technical Properties
- Type: reflective foil/kraft sarking — Class B per AS 4200.1
- Emissivity: ε < 0.05 — reflective — contributes to Section J Rf value
- Width: 1,350 mm and 1,200 mm — length: 30 m per roll standard
Limitations
- Class B vapour barrier — not suitable where vapour permeance is the design intent — use Class A
- Not suitable for passive house or high-performance envelopes — use Pro Clima EXTASANA
- Must have 25 mm air gap to reflective surface for thermal barrier function
PROCUREMENT SOURCES
Confirm suitability with the current manufacturer TDS before specifying or applying.
System Comparison
Side-by-side comparison of wall wrap and sarking systems. Confirm all product selections against the current manufacturer TDS before specifying.
| Product system | Brand | Type | Class | Sd value | Reflective | Airtight laps | Primary use |
|---|---|---|---|---|---|---|---|
| Ametalin ThermaWall | Ametalin / CSR | Breather membrane | Class A (permeable) | < 0.1 m | No | No | Standard coastal cladding — vapour-permeable |
| Kingspan Kooltherm W1 | Kingspan / Bradford | Reflective vapour barrier | Class B (barrier) | > 20 m | Yes | No | Thermal + vapour control — Section J |
| Pro Clima EXTASANA | Pro Clima Australia | Breather membrane | Class A (permeable) | < 0.02 m | No | Yes — Tescon tape | Passive house / airtight envelope |
| CSR Sisalation 450 | CSR Bradford | Reflective sarking | Class B (barrier) | > 20 m | Yes | No | Standard residential cladding |
Do not confuse vapour-permeable wall wrap / sarking with:
- Vapour barrier membrane (non-permeable) — a vapour barrier prevents all moisture vapour from passing through; in a drained-cavity cladding system where inward drying is required, a vapour barrier can trap moisture inside the wall — specify vapour-permeable wall wrap, not vapour barrier, unless the design requires vapour control
- Foil-faced reflective sarking used as wall wrap — standard foil sarking has very low vapour permeance and acts as a vapour barrier, not a breather membrane; in walls where moisture must dry outward, foil sarking on the warm side of insulation is incorrect — verify Sd value before specification
- Polyethylene builder's film — basic PE film has no vapour permeance and no moisture-vapour management function; it acts as a vapour barrier only and is not suitable as a wall wrap in a breathable wall system — not compliant with NCC 2022 requirements for sarking in framed external walls
- Self-adhesive flashing tape — self-adhesive peel-and-stick membrane tape is designed for lapping wall wrap joints, sealing around penetrations, and flashing details; it is not a wall wrap and must not be used as a continuous wall wrapping membrane
Disclaimer
Information is general only. Wall wrap and sarking selection, installation, lapping, and integration with flashings and cavity drainage must be confirmed by a building envelope engineer. An incorrectly installed or vapour-impermeable wrap can trap moisture in the wall assembly. Do not rely on this reference as a substitute for professional engineering advice.