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620 RENEWING EXISTING COVERINGS
• Areas to be renewed site specific.
• Substrate: Do not damage.
• Timing: Remove only sufficient coverings as will be renewed and made
weathertight on same day.

640 FIXING TIMBER TRIMS
• Fasteners: Sherardized steel screws.
• Fixing centres (maximum): 600 mm generally but additional fixings as required to
edges and trims.

650 LAYING METAL DECK OVERLAY
• Setting out: Lay boards with staggered joints and long edges at right angles to
troughs in deck.
- Joints: 1 mm per metre panel size.
- End joints: Centre over crown of deck.
• Fasteners:
- Type: As fastener manufacturer's recommendations.
- Fixing: Determined by contractor.
- Fastener heads: Flush with, or below board surface.

660 JOINTS IN RIGID BOARD SUBSTRATES
• Cover strip: Lay centrally over substrate joints before laying vapour control layers or
coverings. Adhere to substrate with bonding compound along edges only.

670 LAYING VAPOUR CONTROL LAYER
• Laying: Loose laid, flat and smooth.
• Side and head laps: 50 mm and 75 mm respectively. Seal using materials and
method as membrane manufacturer's/ supplier's recommendations.
• Upstands, kerbs and other penetrations: Enclose edges of insulation. Fully seal at
abutment by bonding or taping.

680 LAYING WARM DECK ROOF INSULATION
• Setting out:
- Long edges: Fully supported and running at right angles to direction of span.
- End edges: Adequately supported.
- Joints: Butted together.
- End joints: Staggered.
• Attachment: site specific.
• Mechanical fixing: Six screws and washers per board to agreed pattern.
• Completion: Boards must be in good condition, well fitting and secure.

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