DriStud RU24 Roof Underlay Vapour Permeable Synthetic Self Support Roof Underlay (Non Fire Retardant)

DriStud RU24 is non-fire retardant self-supporting black faced synthetic roofing underlay.

It is a tri-laminate consisting of engineered synthetic materials and it is water resistant and vapour permeable. DriStud RU24 must not be installed where fire retardant roof underlay is specified.

It is intended for use on new and existing buildings in wind zones up to and including ‘Extra High’, as defined in NZS 3604:2011.

Roll Sizes

  • 1250mm x 40.0m (50m²)
  • 1500mm x 40.0m (60m²)
  • 2200mm x 50.0m (110m²)


  • CodeMark™ Certified
  • Self-supporting
  • Can be installed over timber and steel roof framing
  • Breathable & Absorbent
  • UV exposure: 10 days
  • Direct fix with absorbent and non-absorbent cladding including metal
  • Low cost synthetic underlay with FR Index of 9 (Non Fire Retardant)
  • Easier and Quicker to install with 150mm laplines

Overlaps / support

DriStud roofing underlays must be installed with all writing and imagery facing out and with as minimal a number of overlaps as possible. Where overlaps are unavoidable a lap of 150 mm minimum must be used. DriStud RU 24 must not span more than 1.2 m between adjacent supports.


If installing on a roof with a pitch greater than 10° then DriStud roofing underlays may be installed either horizontally or vertically.

If the roofs pitch is 10° or less it is recommended to be run horizontally with the higher layers sitting on top of the lower layers. It can be installed without supporting netting for horizontal installation.

When it is not practical to place underlay horizontally, DriStud RU 24 can be run vertically on a minimum side lap of 150 mm. Underlays must be pulled taut to ensure there are no saggings. If any doubt, it is recommended the joins are taped.

The netting and underlays must be installed flat and taut to ensure condensation will drain to the gutter. If any doubts vertical laps are recommended to be sealed with 75mm DriStud Cool window flashing tape or DriStud Joining Tape to ensure it.

DriStud RU 24 must have support on netting or safety mesh if used: * On roof pitches less than 10° when installed vertically * If support spacing > 1200mm

When DriStud roofing underlays are being used in conjunction with masonry tiles, anti-ponding boards should be used at the lower edges of the tiles.

Technical Properties

Property Standard Value
Roll Sizes (m²) 1250mm x 40m (50m²), 1500mm x 40m (60m²), 2200mm x 50m (110m²)
Weight (m²) 170 ±5 g/m2
Flammability index AS1530.2-1993 9
Fire Retardant No
Water Vapour Resistance ASTM E96 Procedure B Requirement ≤7 MNs/g; Pass
Absorbancy AS/NZS 4201: Part 6 Requirement ≥150 g/m²; Pass
Air Resistance BS ISO 5636-5:2003 ≥0.1 MN s/m³; Pass
Air Barrier Yes
Water Resistance AS/NZS 4201.4:1994 ≥100mm H₂O; Pass
Resistance to UV exposure ASTM G155 10 days
Durability (years) 50
Supported Self Supporting
Roof Pitch ˃ 3°