DriStud RU22 Roof Underlay

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

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DriStud RU22 is a 145 gsm, grey faced, self-support, synthetic roof underlay. It is micro porous, water resistant film that is laminated to two layers of non-woven spunbonded polyolefin. DriStud RU22 is non-fire retardant. DriStud RU22 can be used to line roofs, walls and ceilings.

DriStud RU22 is intended for use on buildings designed in accordance with NZS 3604:2011 paragraph 1.1 and in wind zones up to and including ‘Extra High’. DriStud RU22 is designed to be used as a replacement for self-supporting kraft paper roof underlay. It can be installed over both timber and steel framing to ensure a dry roof cavity. DriStud RU22 can be used under masonry tiles, metal tiles and profiled metal roof claddings. However, DriStud RU22 must not span more than 1.2 m between adjacent supports.

CodeMark Certified


  • CodeMark™ Certified
  • Self-supporting
  • Can be installed over timber and steel roof framing
  • Breathable & Absorbent
  • UV exposure: 7 days
  • Direct fix with absorbent and non-absorbent cladding including metal
  • Low cost synthetic underlay with FR Index of 9 (Non Fire Retardant)
  • DriStud RU22 can be used to line roof, wall and ceiling

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 RU22 must not span more than 1.2 m between adjacent supports.

Weight (m²)145 ±5 g/m2
Flammability indexAS1530.2-1993≤ 5
Fire RetardantNo
Water Vapour ResistanceASTM E96 Procedure B≤ 7MN s/g; Pass
AbsorbancyAS/NZS 4201: Part 6Requirement ≥150 g/m²; Pass
Water ResistanceAS/NZS 4201.4:1994≥100mm H₂O; Pass
Resistance to UV exposureASTM G1557 days
SupportedSelf Supporting
Roof Pitch˃3°


RU22 is affected by exposure to UV radiation and should not be installed where it is exposed to prolonged sunlight.

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 RU22 can be run vertically on a minimum side lap of 150 mm. Underlays must be pulled taut to ensure there are no sagging. 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 RU22 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.

Available Sizes


1250mm x 40.0m (50m²)