Ventia Metal Underlay with Integrated Drainage Mat (1.5m x 25m / 37.5m²) is a specialized, high-performance roof underlay engineered specifically for profiled metal and standing seam roofing systems, imported and supplied throughout New Zealand exclusively by EBuilt Ltd (EProducts NZ Ltd).

Manufactured in Poland by mdm NT—one of Europe’s leading producers of technical building wraps—Ventia Metal combines the highly breathable Ventia Iron microporous underlay with an integrated 3D polymer drainage mat. Produced under a sustainable zero-waste philosophy that recycles post-production waste to eliminate atmospheric factory emissions, Ventia Metal exceeds New Zealand Building Code standards, delivering ultimate drainage, ventilation, and moisture protection for metal roof assemblies.

Advanced Technical Quality & Material Construction

Ventia Metal combines heavy-duty membrane protection with an integrated drainage filament matrix:

• High-Permeability Microporous Base: Features the Ventia Iron 3-layer microporous underlay as its foundation, blocking liquid water ingress while providing maximum vapour diffusion to allow roof space moisture to escape freely.

• Integrated 3D Polymer Drainage Mat: A 7 mm thick polymer filament matrix adhered directly to the top face of the underlay. This mat creates a continuous drainage space between the underlay and the underside of profiled metal roof cladding.

• Heavyweight Physical Profile: Supplied in 1.5m x 25m rolls covering 37.5m², with a total nominal mass of 430 g/m² and a thickness of 7 mm (+/- 2 mm). It delivers robust tensile strength (330 N/50mm machine direction / 200 N/50mm cross direction) and high nail-shank tear resistance (190 N machine direction / 255 N cross direction).

Core Performance Benefits

• Continuous Ventilation & Condensation Drainage Gap: The integrated 7 mm polymer drainage mat creates an uninhibited air cavity beneath metal roof claddings. This enables rapid drainage of underside condensation and wind-driven moisture, preventing standing water contact and extending the serviceable life of metal roofing.

• Acoustic Sound Damping: The 3D filament mat acts as an acoustic decoupling layer, significantly dampening rain impact noise on profiled metal and standing seam roofs for quieter indoor environments.

• Exceptional Vapour Permeability: Featuring an ultra-low Sd value of 0.020 m and water vapour resistance well under the 7 MN s/g NZBC limit, it allows internal humidity to escape rapidly into the ventilated roof cavity, protecting timber sarking from rot and mould growth.

• Substrate & Cladding Integration: BRANZ appraised (Appraisal No. 1136) for installation under profiled metal roof claddings over clean, dry plywood (minimum 7 mm H3) or Strandsarking panels (H3.1) on roof pitches from 3° and above.

• All Wind Zones Coverage: Fully approved for use across all NZS 3604 Building Wind Zones up to and including Extra High, achieving Class W1 liquid water penetration resistance for secondary weather protection.

• Corrosion Protection for Metal Roofs: By physically separating metal roof claddings from the underlying underlay sheet, it prevents moisture entrapment and chemical interactions with underside metal coatings.