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515 EXISTING FLASHINGS
• General: Raise flashings to clean surfaces to receive coatings.
• Timing: Leave raised during coating application and lower only after full curing.
• Damaged lengths: Replace with new, specified in another section: H.

520 PRELIMINARY POWER WASH TO EXISTING COVERINGS
• Timing: Before renewing existing coverings, water jet clean all areas. Allow to dry.

525 RENEWING EXISTING SUBSTRATES/ COVERINGS
• Areas to be renewed: site specific.
• Timing: Remove only sufficient substrates/ coverings, as will be renewed and made
weathertight on same day.

530 MAKING GOOD EXISTING LIQUID APPLIED WATERPROOF COATINGS
• General: Inspect for adherence and repair defective areas in accordance with
proposed coating manufacturer's recommendations.

535 MAKING GOOD EXISTING REINFORCED BITUMEN MEMBRANE COVERING
• Blisters: Star cut, dry out and rebond.
• Cracked and defective areas: Cut back to substrate.
• Substrate: Dry out.
• Bitumen membrane: Patch level with existing surface with layers of matching
bitumen membrane, lapped minimum 100 mm onto existing membrane.

540 MAKING GOOD EXISTING MASTIC ASPHALT COVERING
• Defective areas: Soften and carefully cut out.
• Hammers, chisels, etc.: Do not use to cut cold mastic asphalt.
• Substrate: Dry out.
• Separating membrane: Make good.
• Mastic asphalt: Patch level with existing surface in two coats, the top coat lapped
minimum 75 mm onto existing mastic asphalt and to half its depth.

545 MAKING GOOD EXISTING FIBRE CEMENT SHEET COVERING
• Loose and soft surfaces: Wet and remove. Allow to dry.
• Cracked and damaged sheets: Replace.
• Bolt heads: Tighten and crop where necessary.
- Corrosion and oxidation: Abrade back to bright metal.
• Asbestos based materials: Making good or removal must be carried out by a
contractor licensed by the Health and Safety Executive prior to commencement of
other works in their location.

550 MAKING GOOD EXISTING METAL SHEET COVERING
• Loose coatings: Remove.
• Corrosion and oxidation: Abrade back to bright metal.
• Structurally unsound sheets: Replace.

555 MAKING GOOD EXISTING CEMENTITIOUS SLABS/ SCREEDS
• Loose surfaces, sharp edges and projections: Remove.
• Hollow surfaces, voids and cracks: Fill with cement based repair mortar.

RotF generic (intermediate) NBS 2014 6118-AEW-XX-XX-NBS-A-01