RussFast HR Underlay

RussFast HR Underlay is a heavy-duty underlay which is suitable for both warm and cold roof constructions and is used in conjunction with high and low level ventilation. Manufactured using high-quality material, the underlay offers high performance in all UK locations, providing resistance against wind uplift on the roof and acting as a reliable secondary barrier against wind-driven rain and snow.

Roll Size: 45m x 1m

Resistance to wind pressure – 1732Pa, tested to BS5534.
Fully independently certified by BM Trada.
UKCA marked.

Key features

• Can be used in all UK locations (zones 1-5)
• Excellent nail tear strength
• Fully watertight and airtight
• Absorbent undersurface prevents condensation drop off
• Easy to cut and lightweight for handling
• No tapes required

Technical Information
Weight145 (-5) gsm
Resistance to water penetration
Before artificial ageing:
After artificial ageing:

Class W1
Class W1
Maximum tensile strengthMD
265 (-15)N/50mm
260 (-15)N/50mm
250 (-25)N/50mm
215 (-25)N/50mm
Before artificial ageing:
After artificial ageing:

80 (+5)%
60 (-0)%

100 (+0)%
70 (-0)%
Tear Resistance (nail shank)180 (-30)N200 (-25)N
Flexibility at Low Temperature-40°C
Reaction to Fire(NPD)