GENERAL
Cross-reference
General: Read with A90 General technical requirements.
PRODUCTS
Copper strip and sheet
Standard: To BS EN 1172, rolled, material designation Cu-DHP.
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Stamped or labelled with material condition designation, nominal thickness and finish.Nails for fixing clips
Type:
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To copper clips: Copper nails to BS 1202-2.•
To stainless steel clips: Stainless steel (austenitic) nails. Shank type: Annular ringed or helical threaded.Shank diameter: 2.65 mm (minimum). Head: Flat.
Length: 25 mm (minimum) or equal to substrate thickness.
Screws for fixing clips to concrete/ masonry substrates
Type:
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To copper clips: Brass screws to BS 1210, table 3.•
To stainless steel clips: Stainless steel (austenitic) screws to BS 1210, table 4. Diameter: 3.35 mm (minimum).Length: 25 mm (minimum).
Washers and plastic plugs: Compatible with screws.
Screws for copper or stainless steel clips to composite metal decks
Type: Self tapping, as recommended by the deck and copper manufacturer/ supplier.
Sealant to flashings at masonry joints
Standard: To BS EN ISO 11600.
Underlay
Type:
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Geotextile: 220 g/m² needle punched polyester.EXECUTION
Workmanship generally
Standard: Generally to CP 143-12 and latest editions of Copper Development Association publications. Fabrication and fixing: To provide a secure, free draining and completely weathertight installation.
Operatives: Trained in the application of copper coverings/ flashings. Submit records of experience on request. Preforming: Measure, mark, cut and form copper prior to assembly wherever possible.
Marking out: With pencil, chalk or crayon. Do not use scribers or other sharp instruments without approval.
Folding: With mechanical or manual presses to give straight, regular and tight bends, leaving panels free from ripples, kinks, buckling and cracks. Use hand tools only for folding details that cannot be pressed mechanically.
Sharp metal edges: Fold under or remove as work proceeds.
Free edges: Fold under by 10 mm to provide additional stiffness (folding allowance in addition to any specified length/ width). Finished copper work: Fully supported, adequately fixed to resist wind uplift and able to accommodate thermal movement without distortion or stress.
Protection: Prevent staining, discolouration and damage by subsequent works.
Forming details
Folding and welting: Do not thin, cut or split copper strip/ sheet.
Soldering: Use only where there is no risk of thermal movement stresses at the joint.
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Seams: Neat and consistent with 10 mm overlap of bright copper.•
Solder: Sn Cu3 to BS EN ISO 9453, with a nonacidic flux. Remove flux residues as work proceeds. Brazing: Use only where there is no risk of thermal movement stresses at the joint.•
Seams: Neat and consistent with 10 mm overlap of copper.•
Solder: Cu P6 to BS EN 1044.Existing metal removed to remain the property of the employer
Removal: Give notice when the metal is to be stripped.
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Handling/ Storage: Keep for reuse by the Employer.Suitability of substrates
Preparation of existing timber substrates
Remedial work: Adjust boards to level and securely fix. Punch in any protruding fasteners and plane or sand to achieve an even surface.
Defective boards: Give notice.
Moisture content: 22% (maximum) at time of covering.
Plywood underlay
Standard: Manufactured to an approved national standard and to BS EN 636, section 7 (plywood for use in humid conditions).
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Sheet size 2400 or 1200 x 1200 mm and 6 mm thick. Moisture content: 22% (maximum) at time of covering.Laying: Parallel with perimeter edges with cross joints staggered and a 0.5–1 mm gap between sheets.
Fixing: With 25 mm annular ringed shank copper or stainless steel nails, at 300 mm grid centres over the area of each sheet and at 150 mm centres along edges, set in 10 mm from perimeter edges.
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Nail heads: Set flush or just below the surface.Timber for use with copper work
Quality: Planed, free from wane, pitch pockets, decay and insect attack (ambrosia beetle excepted). Moisture content: 22% (maximum) at time of covering.
Preservative treatment: Organic solvent as section Z12 and Wood Protection Association – Commodity Specification C8.
Underlay
Handling: Prevent tears and punctures.
Laying: Butt or overlap jointed onto a dry substrate.
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Fixing edges: With copper or stainless steel staples or extra large head clout nails. Batten rolls: Fit over underlay.Protection: Keep dry and cover with copper at the earliest opportunity.
Valley gutter lining to slate or tiled roof
Laying: Over and beyond tilting fillets. In 2 m (maximum) lengths.
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Cross joints: Double lock welts.Fixing: Fold edges and fix with copper clips at 450 mm (maximum) centres. Dress bottom end neatly into eaves gutter.
Recessed valley gutter lining to copper roof
Laying: In 2 m (maximum) lengths.
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Cross joints: Double lock welts.Joint with roof covering: Fold copper lining into valley. Turn edges up against bottom of strip/ sheet roofing and fold down into standing seams parallel along each side of valley leaving a central gap of 150 mm (minimum). Fold abutting roof standing seams down flat to drain water.
Valley gutter lining to copper roof
Laying: In 2 m (maximum) lengths.
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Cross joints: Double lock welts.Joint with roof covering: Fold copper lining into valley. Overlap with strip roofing leaving a central gap of 150 mm (minimum). Join lining and strip roofing together with single lock welts with additional check welts (single lock welts only at gutter pitches above 25°).
Batten roll joints in direction of fall
Copper covering:
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Joint allowances: Form strips/ sheet each side of core with 3 mm gap for thermal movement and upstands to 10 mm above height of core.Fixing copper covering:
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Welt clips over upstands.•
Single lock welt upstands to cappings.Cappings: Copper of same temper, thickness and finish as covering.
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Length: 3 m (maximum).•
Fixing: Single lock welt end to end joints.Standing seam joints in direction of fall
Joint allowances: 45 mm overlap, 35 mm underlap and 3 mm (minimum) gap for thermal movement. Preformed interlocking profiles for overlap and underlap are permitted.
Drip/ step cross joints
Strip/ sheet from below step: Fold up full height of step, with allowance for thermal movement, and project 20 mm for folding into welt.
Form copper underlap/ continuous clip:
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Cover to roof slope: 135 mm (minimum) with anticapillary welt at top edge.•
Projection: 35 mm for forming into drip welt.•
Downstand: 40 mm (minimum) with welt at bottom edge.•
Fixing: To roof slope at 100 mm centres, avoiding through fixings at longitudinal joint positions.Strip/ sheet from above step: Fold over clips and underlap projection. Single welt lightly and fold down at an obtuse angle to form a drip and to allow freedom of movement.
Double lock welt cross joints
Joint allowance: 90 mm overlap and 60 mm underlap. Underlap: Welt and secure with clips, one per bay.
Overlap: Double welt overlap around underlap and clips, and dress down.
Single lock welt cross joints
Joint allowance: 100 mm overlap and 50 mm underlap. Overlap: Welt around underlap and dress down.
Forming: Fold welts lightly to allow freedom of movement.
Single lock welt cross joints with additional welt joints
Underlap: Welt top edge and secure with two clips per bay.
Overlap: Fold 250 mm (minimum) over underlap, welt bottom edge and secure with continuous clips soldered or brazed to underlap.
Forming: Fold welts lightly to allow freedom of movement.
Ridge/ Hip batten rolls
Roof coverings: Fix two clips to each roof bay. Form roof coverings each side with upstands to 10 mm above height of core. Welt clips over upstands. Single lock welt upstands to cappings.
Capping: Copper of same temper, thickness and finish as roof, in 3 m (maximum) lengths, with single lock welt end to end joints.
Ridge/ Hip standing seams
Form: Strip/ sheet from each side into a ridge/ hip upstand. Fold down with a double lock welt to an upstand height of 25 mm (minimum).
Abutting roof standing seams: Fold down flat and turn up into ridge/ hip double lock welt.
Standing seam eaves with closed ends
Copper underlap:
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Projection: 20 mm for forming into drip welt.•
Avoid through fixings at standing seam positions.Roof covering: Fold around underlap projection and single welt to form a drip.
Standing seam eaves with folded down ends
Copper underlap:
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Projection: 20 mm for forming into drip welt.•
Fix: Avoid through fixings at standing seam positions. Standing seams:•
Ends: Fold with equal splays.Roof covering: Fold around underlap projection and single welt to form a drip.
Batten roll eaves
Copper underlap:
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Projection: 20 mm for forming into drip welt.•
Fix: Avoid through fixings at batten roll positions.Batten roll cores: Fix over underlap, notching over anticapillary welt. Cut core ends with equal splays. Roof tray upstands and batten roll capping ends: Close with welts to form a weathertight termination. Roof covering: Fold around underlap projection and single welt to form a drip.
Batten roll verge
Top edge:
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Batten roll longitudinal joint: Position flush with verge.•
Forming: Secure top of verge under batten roll cappings with batten roll clips. Bottom edge:•
Continuous clips: Fix at 200 mm centres.Standing seam verge
Top edge:
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Standing seam longitudinal joint: Position flush with verge.•
Forming: Secure top of verge into double welt and clips of standing seam. Bottom edge:•
Continuous clips: Fix at 200 mm centres.•
Forming: Secure bottom of verge around clip with fold.Welted verge
Roof covering: Project 50 mm. Beyond edge of verge. Verge:
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Bottom edge: Fix continuous clip at 300 mm centres. Fold bottom of verge around clips.•
Top edge: Fix clips at 300 mm (maximum) centres. Fold top of verge, clips and roof covering into single welt. Fold down vertically into drip.Standing seam fixed clips
Copper clips: Cut from strip/ sheet of same temper and thickness as that being secured.
Stainless steel (austenitic) clips: Cut from the same thickness of metal as the copper being secured. Dimensions:
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Width: 38 mm (minimum).•
Base length: 25 mm (minimum).•
Upstand: To suit standing seam profile.Fixing: Secure each clip to substrate with two fixings.
Standing seam sliding clips
Copper clips: Cut from strip of same temper and thickness as that being secured.
Stainless steel (austenitic) clips: Cut from the same thickness of metal as the copper being secured. Dimensions of fixed component:
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Width: 90 mm (minimum).•
Base length: 25 mm (minimum).•
Upstand: 20 mm height with 60 mm length slot. Dimensions of sliding component:•
Width: 40 mm (minimum), folded through centre of slot.•
Upstand: Fishtail upstands of 50 mm and 60 mm. Fixing: Secure each clip to substrate with three fixings.Batten roll clips
Material: Cut from strip/ sheet of same temper and thickness as that being secured. Dimensions:
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Width: 38 mm (minimum).•
Length: Sufficient to pass under batten and turn up each side, with 25 mm projections for folding into welt. Fixing: Secure each clip to substrate with copper nail or brass screw through batten.Ridge/ Hip batten roll clips
Material: Cut from strip/ sheet of same temper and thickness as that being secured. Dimensions:
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Width: 50 mm (minimum).•
Length: Sufficient to pass under batten and turn up each side, with 25 mm projections for folding into welt. Fixing: Secure each clip to substrate with copper nail or brass screw through batten.Clips for flashings and cross joints
Material: Cut from strip/ sheet of same temper and thickness as that being secured. Dimensions:
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Width: 50 mm (minimum).•
Length: To suit detail.Fixing: Secure each clip to substrate with minimum two fixings, 50 mm (maximum) from edge of copper strip/ sheet. Clips folded around edges of strip/ sheet to be turned over 25 mm.
Continuous clips (cleats)
Material: Cut from strip/ sheet of same temper and thickness as that being secured. Dimensions:
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Width: To suit detail.•
Length: 1800 mm (maximum).Wedge fixing into joints and chases
Joint/ Chase: Rake out to a depth of 25 mm (minimum).
Copper: Fold 25 mm into joint/ chase with a 2 mm end upstand waterstop.
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Fixing: Copper wedges at 450 mm (maximum) centres, at every change of direction and with at least two for each piece of copper.Wedge fixing into damp proof course joints
Joint: Rake/ Cut out under damp proof course to a depth of 25 mm (minimum). Copper: Fold 25 mm into joint with a 2 mm end upstand waterstop.
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Fixing: Copper wedges at 450 mm (maximum) centres, at every change of direction and with at least two for each piece of copper.Screw fixing into joints and chases
Joint/ chase: Rake out to a depth of 25 mm (minimum). Copper: Fold into joint/ chase and up back face.