DriStud Synthetic Roofing Underlays Engineered for All NZ Weather Conditions

Specifically designed and tested to the NZ Building Code standard, DriStud Synthetic Roofing Underlays are weathertight and are an essential element within the moisture management system within roofs.

TCL Hunt offers four different types of DriStud Synthetic Roofing Underlay — two fire retardant and two non-fire retardant.

Where fire retardant roofing underlays are specified, either FRU 38 (Self Support) or FRU 36 (Heavy Weight) are recommended.

DriStud non-fire retardant roofing underlays RU 24 (Self Support) and RU 22 (Heavy Weight) are economical and are a great alternative to bituminous based roofing underlays — recommended when fire retardancy is not required.

DriStud Roofing Underlay Property Chart
	FRU 38	FRU 36	RU 24	RU 22
CodeMark Certified	•	•	•	•
Self-Support	•		•
Heavy Weight		•		•
Fire Retardant	•	•
FR Index	1	1	9	17
Breathable	•	•	•	•
Absorbent	•	•	•	•
Durability: 50 years (B2.3.1 (a))	•	•	•	•
Wind Zones up to and including 'Extra High' (NZS 3604:2011)	•	•	•	•
Can be installed over timber and steel roof framing	•	•	•	•
Can be direct fixed behind all claddings	•	•	•	•
Can be used for skillion roofs, commercial and industrial roofing	•	•	•	•

DriStud Synthetic Roofing Underlays meet NZ Building Codes B2, E2, C3 and all roofing underlay requirements as referenced in MRM Code of Practice:-

To provide a temporary means for the accumulation of condensation by absorption
To provide a permeable membrane to allow the passage of water vapour
To prevent the ingress of external moisture into roof or wall cavities
To provide a separation barrier between the metal cladding and copper preservative treated timber.

Property Parameters for FRU 38 and FRU 36 (Tested according to NZ Standard 2295:2006):-
	1. Water Vapour Resistance	2. Absorbency	3. Water Resistance	4. Flammability
Test Method	ASTM E 96 Procedure B	AS/NZS 4201: Part 6	AS/NZS 4201.4:1994	AS 1530.2:1993
Roofing Underlay Requirements	≤ 7MNs/g	≥ 150 g/m²	≥ 100mm head water	≤ Index 5
FRU 38 Fire Retardant, Self Support Roofing Underlay	Pass	225 g/m²	Pass	Index 1
FRU 36 Fire Retardant, Heavy Weight Roofing Underlay	Pass	≥ 160g/m²	Pass	Index 1

DriStud's synthetic roofing underlays are intended for use on new and/or existing buildings with steel or timber framing. The roofing underlay must be installed according to and comply with the New Zealand Building Code.

DriStud FRU36 — Fire Retardant Synthetic Self Support/Heavy Weight Roof Underlay

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DriStud FRU36 is a white synthetic tri-laminate roofing underlay that is water resistant, vapour permeable and fire retardant.

DriStud FRU36 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 FRU36 is designed to be used as a replacement for standard kraft paper roof underlay.
It can be installed over both timber and steel framing to ensure a dry roof cavity.
DriStud FRU36 can be used under: masonry tiles, metal tiles, profiled metal roof claddings. However, DriStud FRU36 must be fully supported with a corrosion resistant material where roof pitch is less than 10 degree.

Where CodeMark is to be relied upon, then all conditions of that certificate must be met. These are:

Must be installed in accordance with the DriStud FRU 36 Installation Guide Rev 1.
DriStud FRU36 may be installed over timber and steel roof framing.
The certificate covers the use of DriStud FRU 36 under: masonry tiles, terracotta tiles, metal tiles, profiled metal claddings, slate and composite panels.
DriStud FRU36 can span upto 1200mm.

When specified and installed in accordance with the requirements of the Installation Guide, DriStud FRU 36 roofing underlay will comply with the following provisions of the NZ Building Code:

Clause B1 Structure: B1.3.1, B1.3.2, B1.3.3 (a, h)
Clause B2 Durability: B2.3.1(a), B2.3.2(b) (15 years)
Clause C Protection from Fire: C3.4(c)
Clause F2 Hazardous Building Materials: F2.3.1

CodeMark

DriStud FRU38 — Fire Retardant Synthetic Self-Support Roof Underlay

DriSpace

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DriStud FRU38 is a white synthetic tri-laminate roofing underlay that is water resistant, vapour permeable and fire retardant.

DriStud FRU38 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 FRU38 is designed to be used as a replacement for standard kraft paper roof underlay.
It can be installed over both timber and steel framing to ensure a dry roof cavity.
DriStud FRU38 can be used under: masonry tiles, metal tiles, profiled metal roof claddings.

Where CodeMark is to be relied upon, then all conditions of that certificate must be met. These are:

Must be installed in accordance with the DriStud FRU38 Installation Guide Rev 1.
DriStud FRU 38 may be installed over timber and steel roof framing.
The certificate covers the use of DriStud FRU 38 under: masonry tiles, terracotta tiles, metal tiles, profiled metal claddings, slate and composite panels.
DriStud FRU38 can span up to 1200mm between adjacent supports. Where the span exceeds 1200mm a corrosion resistant mesh or alternative i.e. plastic strapping must be used.

When specified and installed in accordance with the requirements of the Installation Guide, DriStud FRU 36 roofing underlay will comply with the following provisions of the NZ Building Code:

Clause B1 Structure: B1.3.1, B1.3.2, B1.3.3 (a, h)
Clause B2 Durability: B2.3.1(a), B2.3.2(b) (15 years)
Clause C Protection from Fire: C3.4(c)
Clause F2 Hazardous Building Materials: F2.3.1

CodeMark

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