RussFast LR Underlay provides a high level of vapour permeability – helping to avoid the risk of harmful condensation, whilst remaining completely airtight. Manufactured using high-quality material, the underlay offers a 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: 50m x 1m
Certification
Resistance to wind pressure – 1676Pa, 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
• Helps to alleviate condensation risk in the roof space in accordance with BS5250
• Easy to cut and lightweight for handling
• No tapes required
| Technical Information | ||
|---|---|---|
| Weight | 184 (-8) gsm | |
| Resistance to water penetration Before artificial ageing: After artificial ageing: | Class W1 Class W1 | |
| Maximum tensile strength | MD 320 (-20)N/50mm 330 (-20)N/50mm | CD 300 (-30)N/50mm 290 (-20)N/50mm |
| Elongation: Before artificial ageing: After artificial ageing: | 90 (+15)% 70 (-25)% | 90 (+15)% 70 (-25)% |
| Tear Resistance (nail shank) | 190 (-15)N | 200 (-15)N |
| Flexibility at Low Temperature | -40°C | |
| Water Vapour Resistance | <0.10MNs/g | |
| Equivalent Air Layer Thickness | <0.02sd(m) | |
| Reaction to Fire | (NPD) | |
