DriStud FRU36 Roof Underlay 155gsm Fire Retardant Synthetic Self-Support Roof Underlay

DriStud FRU 36 is white synthetic tri-laminate roofing underlays that are water resistant, vapour permeable and fire retardant. The FRU 36 is a self support roof underlay however FRU 36 can be used for both self support and heavy weight applications. 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.

DriStud FRU 36 is a lighter grammage self-support roof underlay, whereas DriStud FRU 38 is heavier grammage self-support roof underlay.

Features

  • CodeMark™ Certified
  • Self Supporting
  • Can be installed over timber and steel roof framing
  • Fire Retardant
  • Breathable & Absorbent
  • UV exposure: 10 days
  • Durability: 50 years
  • Direct fix with absorbent and non-absorbent cladding including metal cladding

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 FRU 36 must not span more than 1.2 m between adjacent supports.

Installation

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 DriStud roofing underlays is recommended to be run horizontally with the higher layers sitting on top of the lower layers. When it is not practical to place underlay horizontally, DriStud FRU 36 can be run vertically on a minimum side lap of 150 mm. Self-support roof underlays must be installed on supporting netting or equivalent system. 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 tapes to ensure it.

DriStud FRU 36 must have support on netting or safety mesh if used:

  • Under dark coloured metal cladding
  • On roof pitches less than 10°
  • 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
Weight 155 ±5 g/m2
Roll Sizes (m²) 1350mm x 56m (75m²), 1350mm x 18.6m (25m2)
Flammability index AS1530.2-1993 1
Fire Retardant Yes
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°