IKO Glass-Fibre Underlay (3B) is a waterproofing membrane, consisting of a strong glass fibre base coated with oxidised bitumen. It is sand finished on both surfaces.
Used as an economical underlay (or intermediate layer) in a built-up felt roofing, and is usually fully bonded in hot bitumen.
It is also used as an underlay to bitumen shingles in a pitched roof application
British Standard glass-fibre based