Cromar® 1F Underslaters

18 months 

Do not drag rolls across rough surfaces, always lift. Rolls should be stored upright on a dry surface. During colder periods it is recommended that rolls are stored in a temperature above +10 °C for 24 hours prior to use. During storage exposure to direct sunlight is to be avoided. Do not use in temperatures below +5 °C.

1 m x 15 m

1.5 kg/m²

22.5 kg

1060 N/50 mm MD
280 N/50 mm CD

2 % MD
4 % CD

180 N MD
235 N CD

Class F  (BS EN 13501-1)

• Install 1F underslaters felt parallel to the eaves, working from eaves to ridge.
• Lay felt smooth and taut, without stretching, to avoid sagging between rafters.
• Fix felt directly to rafters using galvanised clout nails, typically at 150-200 mm centres along the top edge.
• Provide horizontal laps of minimum 150 mm and vertical end laps of minimum 100 mm, staggered between courses.
• At the eaves, dress felt into the gutter or over the eaves support tray to ensure effective water run‑off.
• At valleys, hips, and abutments, cut and dress the felt neatly, maintaining full laps and continuity.
• Finish felt tight into the ridge, lapped over the opposite roof slope where applicable.
• Ensure the covering is installed promptly; 1F felt is not intended for long-term UV exposure.
• Install in accordance with BS 5534 and good roofing practice.