Dimondclad Rib50 Cladding

Layout and Fastening

The following comments are made as guidelines to be used when inspecting Dimond roofing and wall cladding systems during and after installation.

a. Netting

Netting should be run across purlins and be tensioned to remove unnecessary sag. Fastening to timber should be with either galvanised staples or 25mm clouts avoiding contact with the roofing, and to steel with flat head screws.

Fixings should be at 150mm centres on end purlins in such a way that the netting cannot pull past the fixing. Edges of the netting should be tied together or twitched at 300mm centres and fixed to each purlin. Safety mesh should be installed to manufacturers recommendations.

b. Roofing Underlay

Horizontal Application: underlay is unrolled across the roof parallel with purlins and secured as necessary. Joins should be lapped by a minimum of 75mm and supported on netting if roof pitch is below 8 degrees for self supporting and have the side edges supported on purlins.

Vertical Application: underlay is unrolled vertically up the slope of the roof from guttering to ridge and secured to the purlins as necessary before laying the roof sheet and fixing down. Joins should be lapped by a minimum of 150mm. Support such as netting or safety mesh must be used on pitches below 8 degrees, or when using self supporting underlays on purlin spacings greater than 1200 mm.

When used under roofing, all underlays must be supported on wire netting or strapping at 300mm maximum spacings. Self sufficient underlays can be used on purlins spacing up to 1200mm without support. Underlay should overlay into the gutter at least 20mm and not more than 50mm, and avoid lapping into the water flow. Maximum single underlay sheet lengths shall be 10m for bituminous and fire retarded kraft papers. Longer runs are to
be end lapped 150mm. Synthetic underlays have no limit on their run length. In general it is recommended that prolonged exposure of the underlay to the weather is avoided by fixing the roofing over the same day. Always follow underlay manufacturers recommendations.

c. Roofing and Cladding Sheets

Supporting Structure

• Roofing and wall cladding sheets should not be installed until the roofing contractor is satisfied that the support structure is complete, sound, and correctly aligned. This includes support around penetrations and openings.
• Purlin and girt spans both end and internal spacings must be in accordance with Dimond recommendations for profile, metal type and thickness, as well as the expected level of foot traffic. If in doubt, check.
• Curved roofs (whether draped/rolled or crimped) require purlin alignment within ±5mm to minimise the risk of unacceptable finished appearance.
• Spacers must be fixed to steel purlins to allow insulation to fit between and to create a 25mm air gap between underlay and insulation. Do not compress the insulation.

Where the building is under the scope of E2/ASI there is a requirement to install horizontal wall cladding onto a cavity batten system to achieve a 20mm air space between the back of the cladding and wall framing on all walls in accordance with NZBC E2/ASI. Dimond profiles that come within the scope of E2/ASI are: Corrugate, Styleline, Veedek, Dimondek 300, Dimondek 400 and V-Rib.

Vertical run cladding does not require a cavity batten system on any risk matrix wall provided the details and installation is carried out in accordance with recommendations in this manual, which are based on past history where Dimond profiles have successfully been fixed. 

Installation in this way will not be in accordance with E2/ASI: June 05 and is an alternative solution.

Sheet Layout

• Firstly, the sheet should show no signs or evidence of transport damage or storage damage including wet storage effects. If the sheets are damaged they must not be fixed down, and the Dimond supplying branch should be informed as soon as possible.
• Care should be taken to ensure sheets are laid parallel to the lines of building ends, and perpendicular to ridges and gutters. If possible, the direction of laying should be such that the sheet side laps face away from the prevailing wind direction, or, in the case of wall cladding, away from the most common line of sight.
• Side laps must be properly engaged such that the overlap rib fits correctly over the underlay without obvious gaps or insufficient cover.
• Roofing sheets should run continuously from ridge to gutter, avoiding end laps. Long lengths separated for thermal expansion or handling reasons should join at a step in the roof. Where end lapping of straight and curved sheets cannot be avoided, a correctly formed 150mm minimum sealed lap is required, with a bead of neutral curing silicone sealant each end of the lapped sheets.
• Sheet ends should form an even line (within a workable tolerance) and roof sheeting should overhang into gutters by at least 50mm and must allow clearance to enable ease of gutter cleaning. 

Sheet Ends

• All roofing and wall cladding sheet ends that terminate under flashings (regardless of pitch) should be formed with a full vertical dog-eared stop end to the full height of the profile rib. Where a full height dog-eared stop end cannot be achieved, a pull up stop end a minimum 28mm high on all profiles excluding Corrugate must be provided in conjunction with foam profile closures.
• For roofs below 8 degrees pitch the drip edge sheet end should be formed with a down turned lip. 

Sheet Fastening

• Sheet must be fastened to every purlin (or girt) to transfer outward loads evenly to every structural member.
• The screw and washer system used should meet specification requirements and have a durability to at least match that of the sheeting, and be in accordance with Dimond literature for that profile.
• Fasteners must be perpendicular to the sheeting and tightened sufficiently to effect a durable seal without over tightening that results in seal washer distortion or profile crest dishing and depressing. Fixings must be to a line.
• Concealed clips used to fasten Dimondek 300, Dimondek 400 and Dimondek 630 products must not exhibit screw or nail head protrusion such that damage to the roof sheet and coating may result.
• Whenever oversize holes are required to accommodate expansion, profiled washers and seals must be used.
• Profiled washers and seals should be used whenever specified to provide extra wind uplift capacity.
• Note should be made to ensure there are sufficient fasteners, evenly distributed. In particular the perimeter zones of roofs, where maximum wind uplift occurs, must have sufficient fasteners.
• No areas on the roof should hold water that will cause ponding long term. The structure may require realignment and if the profile is damaged, this should be replaced.

Wall Cladding Underlay

• Can be laid either horizontally on steel girts or vertically on timber studs.
• When run horizontally lap upper sheet over lower sheet a minimum of 75mm. Adequately secure to framing at 300mm centres. When installed in high wind areas fix through a reinforced tape such as Danband branded polypropylene tape.
• Run lengths to be no greater than 10m.
• End laps to be no less than 150mm over studs of vertical joints.
• The underlay should be pulled taut as possible.
• Best practice is to clad on the same day as installation provided the product is kept dry and undamaged. 
• Maximum period that the underlays are exposed to the weather is contained in the underlay manufacturers literature

d. Duraclad

The above comments for roofing and cladding sheets generally apply. Additional attention should be given to:

• Stop ends should be correctly formed by attaching a metal (usually aluminium) folded angle to the sheet end, and sealing it in place.
• The supporting structure must be free of abrasive surfaces or irregularities. If used over netting or safety mesh, a barrier strip must be installed to prevent abrasive damage to the sheet surface.
• Fastening of Duraclad requires pre-drilling of the sheet with a hole size that is at least 2mm greater than the fastener diameter. Additional hole size may be required to accommodate thermal expansion of the sheeting.
• 32mm Weatherlok washers must be used as specified.
• Provision should be made during installation to enable foot traffic movement across the roof without applying point loads to the Duraclad sheeting. Planks or temporary walkways are recommended.
• Safety Mesh must be installed underneath Duraclad if the sheet thickness is less than 1.7mm. (If general foot traffic is expected, consult Dimond for the use of products specifically designed for the purpose.)