DATA SHEET Building Paper 728 (BS 1521 - POLYBIT) TYPICAL USES DESCRIPTION Building Paper 728 is a traditional, polythene coated, reinforced bitumenbonded kraft paper laminate. Manufactured with wet-strength kraft paper and meeting the technical requirements of BS 1521, Class A1F, for water-proof building paper, the product utilises polymer reinforcing scrim. Separation Layer Building Paper 728 Typically used where conditions require a material with additional strength and durability. Typical uses: Moisture barrier, Underlays on uninsulated cladding,Temporary Protection, Separation Layers, Bond Breaks, Draught and Damp exclusion barriers and flat lead sheet underlay. 1. DPM • ay black side down over smooth surface (rough surfaces should be sand L blinded to avoid puncture). • Allow 150mm overlaps and seal with tape. TECHNICAL Moisture vapour resistance Liquid water resistance minimum Upper temperature stability Chemical resistance Resistant to chemicals found in plaster and cement Does not attract insects or vermin Roll Specification 2. Concrete Slide/Separation Layer • Lay black side up, allow 100mm overlaps. Roll weight 3. Lead roof underlay • Lay black side up using nails or staples, allowing 150mm overlaps. • Also use under lead in valley gutters.