GENERAL
Cross-reference
General: Read with A90 General technical requirements.
Preservative treatment: Read with Z12 Preservative and fire retardant treatment. Mortar: Read with Z21 Mortars.
PRODUCTS
Tiles
Clay tiles: To BS EN 1304.
Concrete tiles (noninterlocking): To BS EN 490.
Battens, counterbattens and ridge/ hip fixing battens
Timber: To BS 5534, clause 4.12.1.
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Type: Sawn softwood (imported Whitewood, Redwood, Spruce/ Pine/ Fir (Canadian/ USA) or Southern pine (USA) or British grown Corsican pine, Scots pine or Sitka spruce).•
Permissible characteristics and defects limits: Not to exceed limits in BS 5534, annex C.•
Moisture content at time of fixing and covering: 22% (maximum).Preservative treatment: To British Wood Preserving and Damp-proofing Association Commodity Specification C8.
Fasteners
Nails:
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Aluminium nails: To BS 1202-3.•
Copper nails: To BS 1202-2.•
Steel nails: To BS 1202-1 or BS EN 10230-1 as appropriate for specified type.Hip irons
Standard: To BS 5534, clause 4.16.1.
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Material: Galvanized steel.Mortar bedding and pointing
Mortar: 1:3 cement:sand.
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Plasticizing admixtures: Permitted.•
Bond strength: Provide resistance to uplift to BS 5534.Tiling underlay
Reinforced bitumen sheet: To BS 747/ BS EN 13707 and BS 5534, Annex A. Breathable membrane: Agrément certified.
EXECUTION
Tiling generally
Standard: To applicable parts of BS 5534.
General: Fix tiling and accessories to make the whole sound and weathertight at the earliest opportunity. Setting out: To true lines and regular appearance, with neat fit at edges, junctions and features. Fixings for accessories: As recommended by tile manufacturer.
Gutters and pipes: Keep free of debris. Clean out at completion.
Removing existing tiling
General: Carefully remove tiles, battens, underlay, etc. with minimum disturbance of adjacent retained tiling.
Underlay
Handling: Do not tear or puncture. Laying: Maintain consistent tautness.
Vertical laps: 100 mm wide (minimum), coinciding with supports and securely fixed. Fixing: Fix with galvanized steel, copper or aluminium 20 x 3 mm clout head nails. At penetration of pipes and components: Select from:
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Proprietary underlay seals or•
Cut underlay accurately and turn flanges up to give a watertight fit. Ventilation paths: Do not obstruct.Counterbattens
Fixing:
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On rigid sarking: Through rigid sarking into rafters at 300 mm (maximum) centres.•
On rafters: Into rafters at 300 mm (maximum) centres.Battens
Setting out: Align parallel to ridge in straight horizontal lines to gauge of the tile. Align on adjacent areas. Batten length (minimum): Sufficient to span over three supports.
Joints in length: Square cut, butt centrally on supports. Joints must not occur more than once in any group of four battens on any one support.
Unsupported underlay laps between battens: Provide additional battens. Fixing: Each batten to each support. Splay fix at joints in length.
Tile fixing
Setting out: Lay tiles to a half lap bond with joints slightly open. Align tails.
Ends of courses: Use tile and a half tiles to maintain bond and ensure that cut tiles are as large as possible. Top and bottom courses: Use eaves/ tops tiles to maintain gauge.
Fixings for tiles: Nails/ clips recommended by tile manufacturer.
Local and general fixing areas
Definitions:
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Local areas: Bands of tiling around edges or obstructions of each plane of the roof.•
General areas: Remaining areas of roof tiling.Mortar bedding and pointing
Weather: Do not use in wet or frosty conditions or when such weather is imminent.
Preparation of tiles and accessories to be bedded: Wet and drain surface water before fixing. Appearance: Finish neatly as work proceeds and remove residue.
Edges, junctions and features
Fittings and accessories: Proprietary, not improvised.
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Exposed fittings and accessories: Match tile colour and finish. Cut tiles: Only where necessary to give straight, clean edges. Flashings: Fix with or immediately after tiling. Dress down neatly.Fire separating walls
Separating wall: Completely fill space between top of wall and underside of tiles with mineral wool quilt to provide fire stopping. Boxed eaves: Completely seal air paths in plane of separating wall with wire reinforced mineral wool, 50 mm thick (minimum), fixed to rafters. Cut carefully to shape to provide fire stopping.
Integrated grilles/ trays for ventilated eaves
Execution: Fix to carry underlay, form drip into gutter and provide free passage of air over insulation.
Undercourse and first course tiles: Fix with tails projecting 50 mm over gutter or to centre of gutter, whichever dimension is the lesser.
Separated grilles/ trays for ventilated eaves
Execution: Fix to carry underlay, form drip into gutter and provide free passage of air over insulation.
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Underlay support: Continuous to prevent water retaining troughs.•
Gutter: Dress underlay or underlay support tray to form drip into gutter.Undercourse and first course tiles: Fix with tails projecting 50 mm over gutter or to centre of gutter, whichever dimension is the lesser.
Unventilated eaves
Gutter: Dress underlay or underlay support tray to form drip into gutter. Underlay support: Continuous to prevent water retaining troughs.
Undercourse and first course tiles: Fix with tails projecting 50 mm over gutter or to centre of gutter, whichever dimension is the lesser.
Cloaked verges
Underlay and tiling battens: Carry over full width of verge. Project underlay to turn down behind verge tiles.
Mortar bedded verge with bedded undercloak
Underlay: Carry 50 mm onto outer leaf of gable wall and bed on mortar. Undercloak: Matching plain tiles.
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Position: Over underlay, level with underside of tiling battens, sloping towards verge.•
Projection beyond face of wall: 38–50mm.•
Bedding: On mortar identical to that used in gable walling.Tiling battens: Carry onto undercloak and finish 100 mm from verge edge. Verge tiles:
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Bedding: Flush with undercloak on 75 mm wide bed of mortar.Mortar bedded verge with nailed undercloak
Underlay: Carry over full width of verge. Undercloak: Fibre cement sheet.
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Position: Over underlay, level with underside of tiling battens, sloping towards verge.•
Projection beyond face of bargeboard/ fascia: 38–50 mm.•
Fixing: Nailed.Tiling battens: Carry onto undercloak and finish 100 mm from verge edge. Verge tiles:
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Bedding: Flush with undercloak on 75 mm wide bed of mortar.•
Fixing: Nails. Do not displace or crack mortar.Hips
Underlay: Lay courses over hip. Overlap 150 mm (minimum). Dry hips:
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Tiles: Cut and fix closely at hip. Mitred hips:•
Laying: Cut tile and a half tiles and fix to form a straight, close mitred junction.•
Soakers: Interleave with mitred tiles. Fix by turning down over head of mitred tiles. Mortar bedded hips:•
Tiles: Cut and fix closely at junction.•
Bedding: Continuous to edges and solid at joints.•
Fixing: Where rigid masonry walls support or abut hip, secure hip tiles within 900 mm of such walls to hip rafters or supplementary hip battens with nails/ wire ties or screws.•
Bottom hip tiles: Shape neatly to align with corner of eaves.•
Hip irons: Fix to hip rafter or hip batten with (minimum) two zinc coated steel screws. Arris hips:•
Arris hip tiles: Bed in mortar. Course in with roof tiling. Nail to hip rafter or supplementary hip batten.•
Cut adjacent tiles to fit neatly. Bonnet hips:•
Bonnet hip tiles: Bed in mortar neatly struck back about 13 mm from edge of tiles. Course in with roof tiling.•
Fixing: Nail to hip rafter or supplementary hip batten.•
Bottom hip tiles: Fill end with mortar and tile slips finished flush.•
Cut adjacent tiles to fit neatly.Valleys
GRP valleys:
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Underlay: Lay as recommended by GRP valley manufacturer.•
Roof tiles: Cut adjacent tiles to fit neatly. Bed on mortar on GRP valley. Metal valleys:•
Underlay: Cut to rake. Dress over tilting fillets to lap onto metal valley. Do not lay under metal.•
Roof tiles: Cut adjacent tiles to fit neatly. Bed on mortar on fibre cement undercloaks laid loose each side of valley. Curved plain tile valleys:•
Underlay: Lay strips 600 mm (minimum) wide centred on valleys. Underlap general roof underlay.•
Tiles: Cut adjacent tiles to fit neatly.Abutments
Underlay: Turn up 100 mm (minimum) at abutments. Side abutments:
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Abutment tiles: Cut as necessary. Fix close to abutments.•
Soakers: Interleave with abutment tiles. Fix by turning down over head of abutment tiles. Top edge abutments:•
Top course tiles: Fix close to abutments.•
Ventilated abutments: Provide air gap at abutment as recommended by ventilator manufacturer.Roof windows
Underlay: Turn up 100 mm (minimum) at window surrounds under integral flashings/ soakers. Tiles: Cut as necessary and fix closely all round.
Ridges
Dry ridge:
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Underlay: Lay courses over ridge. Overlap 100 mm (minimum). Dry ventilated ridge:•
Underlay: Provide air gap at apex. Mortar bedded tile ridge:•
Underlay: Lay courses over. Overlap 100 mm (minimum).•
Bedding: Continuous to edges and solid at joints.•
Fixing: Where rigid masonry walls support or abut ridge, secure ridge tiles within 900 mm of such walls to ridge boards or supplementary ridge battens with nails/ wire ties or screws.Mono-ridges
Dry mono-ridge:
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Underlay: Lay 100 mm (minimum) over apex. Dry ventilated mono-ridge:•
Underlay: Provide air gap at apex. Mortar bedded mono-ridges:•
Underlay: Lay 100 mm (minimum) over apex.•
Bedding: Mortar, continuous to sloping edges and solid to joints•
Fixing: Secure vertical faces to ridge fixing battens with screws/ nails.Snowguards
Brackets: Fix to rafters on a line 100–150 mm above the roof edge. Tiling: Cut tiles as necessary. Fit flashing and dress over roof finish.
Vertical tiling edges and junctions
Bottom edges: