Decra Classic Roof Specification

Decra

Roof Systems Limited

Specification

Decra Classic

Foreword

This model specification is designed for specifiers of Decra Roof Systems Ltd's products who require National Building Specification (NBS) clauses, for sections H67 Single Lap Metal Roof Tiles.

The model specification provided below is not designed to be exhaustive and is given in good faith. The purpose/extent of the enclosed model specification is to provide an indicative outline of the general processes required to complete a successful Decra Roof. It is not the intent of this model specification to provide step by step guidance covering all aspects and issues that may be relevant to the installation of the specific project.

Important Notes:

Decra Roof Systems recommend that a site survey be undertaken by persons tendering the contract. It shall be the responsibility of the successful contractor to ensure that all necessary preparation and working practices are achieved to produce a level of workmanship and finished appearance resulting in client satisfaction.

Installers must always follow Decra's installation instructions (available at www.decra.co.uk) or contact Decra Roof Systems technical support team if in doubt.

Preliminaries

Insulation should be selected of sufficient depth to ensure that the current recommendations of Building Regulation L (conservation of fuel \& power) and BS 5250: Code of practice for control of condensation are met and current codes of practice should be followed at all times.

Water tanks should be covered and all pipework and ducting must be insulated with appropriate insulants. Loft hatches should be draft sealed and insulated with an equivalent thickness of insulation. All gaps and holes in the ceiling should also be vapour sealed. Care should be taken to maintain a 50 mm air passageway ensuring through ventilation of the loft space via eaves occurs. At all times, insulation should be installed in accordance with the insulation manufacturer's recommendations and current codes of practice.

Leadwork \& Associated Lead Flashings:

As an alternative to the use of traditional lead flashings we have included in this specification for the use of Decra FormFlash. Decra FormFlash is a lead free waterproof flashing for use in all applications where lead is traditionally installed including: stepped flashings, rooflights, abutment flashings, dormers, valleys, chimney flashings and flat/pitched roof junctions.

H67 Metal Single Lap Roof Tiling

To be read with Preliminaries/ General conditions.

General

110 METAL ROOF TILING TO MAIN ROOF

• Substrate: EXISTING FELT ROOF
• Pitch:
• Underlay: As clause 305 and 625A.
• Battens:
• Size: -for 450 mm rafter centres, -for 600 mm rafter centres, 50 mm -for 900 mm \& 1200 mm rafter centres, -for 1500 mm rafter centres.
• Gauge: 370 mm .
• Fixing: With appropriate annular ring or twist shank galvanised nails or screws (strictly in accordance with manufacturer instructions).
• Tiles:
• Product reference: Decra Classic Tile
• Colour: Terracotta / Teak / Brindle / Anthracite / Shiny Black / Sea Green / Client's Choice.
• Manufacturer: Decra Roofing Systems Ltd. Barton Dock Rd. Stretford. Manchester. M32 0YL. Tel: 0161865 4444. Fax: 161864 2616. Email: [email protected] Web: www.decra.co.uk
• Finish and durability: To meet the specified performance requirements. the metal tile and accessories required must: (1) Be manufactured from 0.43 mm thick high quality steel and zinc/aluminium galvanised for maximum performance and durability. The use of Z275 Zinc galvanised coatings is strictly prohibited. (2) Be given a passivation coating with a subsequent epoxy primer applied to both sides to ensure maximum adhesion of subsequent acrylic coating. The use of acrylic as primer coatings is strictly prohibited.

(3) Have a mandatory polyester coating on underside. (4) Subsequent acrylic resin coatings must have a non-toxic fungicide incorporated into the coating for added protection. (5) Have a stone granular finish, which must be ceramically colour glazed before being added to the resin coating, giving a good covering with no gaps between the granules. (6) Have a finishing coat of a clear acrylic resin, incorporating a U.V inhibitor, applied over the granules. (7) The use of a paint as a colour bearing coating final finish is strictly prohibited. (8) Manufactured to ISO 9000 Quality Standards and ISO 14001 Environmental Management Systems. (9) Be independently assessed to have a product life span of in excess of 40 years.

• Tile Size:
• Gauge: 370 mm
• Bond: Straight bond -recommended for simple shapes (i.e. gable to gable roofs). Broken bond -recommended for complex shapes (i.e. hip and valley roofs).
• Fixing: 4 no coated Decra nails per tile located in positions as recommended in Decra Roof Systems installation guides.
• Other requirements: 40-year Weather Security Guarantee (consult with Decra for details and conditions).

Products

300A Tiles At Eaves Course

• Location: Eaves course.
• Manufacturer: : Decra Roofing Systems Ltd. Barton Dock Rd. Stretford. Manchester. M32 0YL. Tel: 0161865 4444. Fax: 161864 2616. Email: [email protected] Web: www.decra.co.uk - Product reference: Decra Classic Anti-Rust Tile.

305A Pitched Roof Underlay

• Type: non-woven polypropylene .
• Manufacturer: : Decra Roofing Systems Ltd. Barton Dock Rd. Stretford. Manchester. M32 0YL. Tel: 0161865 4444. Fax: 161864 2616. Email: [email protected] Web: www.decra.co.uk - Product reference: Monarperm Breathe All Zones

310 BATTENS/ COUNTERBATTENS - TREATED

• Timber: Sawn softwood.
• Standard: BS 5534, clause 4.12.1.
• Permissible characteristics and defects: Not to exceed limits in BS 5534, Annex C.
• Moisture content at time of fixing and covering (maximum): .
• Preservative treatment: As section Z12 and British Wood Preserving and Damp-proofing Association Commodity Specification C8.
• Type: Organic solvent (OS) or CCA as appropriate - see NBS section Z12, table 4. (Note: CCA treated wood must not be used in residential or domestic construction).

320 Eaves Underlay Supports

• Type: Plastic underlay carrier
• Manufacturer: Decra Roofing Systems Ltd. Barton Dock Rd. Stretford. Manchester. M32 0YL. Tel: 0161865 4444. Fax: 161864 2616. Email: [email protected] Web: www.decra.co.uk - Product reference: Decra Eaves Guard 400 [Ref: DXUM400]

325 EAVES VENTS

• Type: Over fascia ventilator strip
• Manufacturer: Decra Roofing Systems Ltd. Barton Dock Rd. Stretford. Manchester. M32 0YL. Tel: 0161865 4444. Fax: 161864 2616. Email: [email protected] Web: www.decra.co.uk - Product reference: Decra Eaves Ventilation System
• Size: 25 mm eaves vent system for roof pitches or less; 10 mm eaves vent system for roof pitches greater than .

330 EAVES VENTILATOR TRAYS

• Type: Continuous rafter roll
• Manufacturer: Decra Roofing Systems Ltd. Barton Dock Rd. Stretford. Manchester. M32 0YL. Tel: 0161865 4444. Fax: 161864 2616. Email: [email protected] Web: www.decra.co.uk - Product reference: Decra Continuous Rafter Roll (is included in the 10mm and 25mm Decra Eaves Ventilation System pack).

340 HIP CAPS

• Manufacturer: Decra Roofing Systems Ltd. Barton Dock Rd. Stretford. Manchester. M32 0YL. Tel: 0161865 4444. Fax: 161864 2616. Email: [email protected] Web: www.decra.co.uk - Product reference: Decra 'D' Ridge [Ref: DD_B1]
• Accessories: Decra 'D' Ridge Hip End Closure Unit [Ref: DD_DH1]

Execution

605 BASIC WORKMANSHIP

• General: Fix metal tiling and accessories to make the whole sound and weathertight at earliest opportunity.
• Setting out: To regular appearance, with neat fit at edges, junctions and features.
• Fixings of accessories: As recommended by metal tile manufacturer.
• Metal tiles: Laps must face away from valley or rainwater discharge pipes on roof.
• Cut metal tiles: Cold cut and treat as recommended by manufacturer. Tiles and accessories must not be cut with an angle grinder.
• Flashings: Fix with or immediately after metal tiling. Form neatly.

615 Fire Separating Walls

• Separating walls: Completely fill space between top of wall and underside of metal 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, not less than 50 mm thick, fixed to rafters and carefully cut to shape to provide fire stopping.

625A Laying Underlay

• Handling: Do not tear or puncture.
• Laying: Maintain consistent tautness.
• Partial Supported: Lay draped across rafter/counter-battens.
• Fully Supported: Lay taut, but not drum-tight. Secure with Counter-battens.
• Vertical laps (minimum): 100 mm wide, coinciding with supports and securely fixed.
• Fixing: Aluminium or steel coated by zinc or zinc alloy, clout head nails.
• Eaves: Where exposed, underlay must be BS 747/ BS 5534, Annex A Type 5U, or an equivalent UV durable type.
• Penetrations: Use proprietary underlay seals or cut underlay to give a watertight fit around pipes and components.
• Ventilation paths: Do not obstruct.

640 FIXING COUNTERBATTENS ON EXISTING FELT COVERING

• Fixing: Into rafters at not more than 300 mm centres.

645 FIXING BATTENS - ROOF TILING

• Setting out: Align parallel to ridge in straight horizontal lines to gauge required by the metal tile. Align on adjacent areas.
• Batten length (minimum): Sufficient to span over three supports.
• Joints in length: Square cut. Butt centrally on supports.
• Rafters up to 600 mm centres: Not more than one batten joint in any four consecutive battens on the same support.
• Rafters over 600 mm centres: Stagger batten joints to avoid coincidence on same support.
• Additional battens: Provide where unsupported laps in underlay occur between battens.
• Fixing: Each batten to each support. Skew fix at joints in length.

655 Fixing Metal Tiles

• Setting out: Lay each course to specified bond.
• Side laps: 64 mm
• Fixing: As recommended by metal tile manufacturer.
• Nail heads: Treat vertically driven nail heads with Decra finishing kit.

660 VENTILATED EAVES FOR COLD ROOF CONSTRUCTION

• Eaves vents: Fix to top of fascia board.
• Ventilator trays: Fix to provide free passage of air over insulation.

• Underlay support: Continuous to prevent water-retaining troughs.
• Gutter: Dress underlay or underlay support tray to form drip into gutter. Ensure gutter brackets are fixed to provide a ventilation path to eaves vents.
• First course metal tiles: Fix with tails projecting 40 mm over gutter or to centre of gutter, whichever dimension is the lesser Seal the heads of vertically driven nails with Decra finishing kit.

675 HIPS

• Underlay: Lay courses over hip.
• Overlaps (minimum): 150 mm .
• Hip fixing battens:
• Size:
• Fixing: To battens.
• Metal tiles: Cut and form to an upstand.
• Hip and end caps: Fix to face of fixing battens with 4no. Decra nail on each side of the D Ridge.

680 VENTILATED HIPS

• Underlay: Lay to provide a 10 mm air gap centred on the hipline.
• Hip fixing battens:
• Size:
• Fixing: To battens.
• Metal tiles: Cut and form to an upstand.
• Ventilator: Position on metal tile to allow fit of ridge cap.
• Hip and end caps: Fix through continuous line of ventilator to face of fixing battens with 4no. Decra nail on each side of the D Ridge

745 VENTILATED RIDGES WITH VENT FIXED UNDER RIDGE FIXING BATTEN

• Underlay: Lay to provide a 10 mm air gap centred on the ridgeline.
• Battens: Position and fix to suit ridge cap profile.
• Metal tiles: Cut and form to an upstand.
• Ventilator: Position D Ridge Vent Filler on metal tile to allow fit of ridge cap.
• Ridge fixing battens:
• Size:
• Fixing: Install on top of D Ridge Vent Filler and secure through tile into underlying battens.
• Ridge and end caps: Fix to face of ridge fixing batten.

770 CHANGE OF ROOF PITCHES

• Tiling substrate work: Set out battens at appropriate gauge from eaves to change of roof pitch. Set out battens at pitch change from front edge of batten. Fix next tile batten at appropriate gauge.
• Metal tiles: Fix courses above and below metal tile change in roof pitch to form a weathertight junction.

775 INSTALLING ROOF SLOPE TERMINALS

• Ventilator tiles:
• Connect to Soil ventilation or Mechanical ventilation extracts (all not exceeding 100mm diameter)

Completion

910 COMPLETION

• Roof area: Clean.
• Rainwater pipes, gutters and outlets: Clear.
• Metal tile profiles: Free from defects.
• Roof edges, junctions and features: Watertight.