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Kāhu Roofing and Cladding System
Description

Kāhu® is a steel roofing and external wall cladding system comprised of a long run steel sheet with a symmetrical profile, along with associated design and installation information.

Kāhu features a double capillary overlap to the side lap which allows for weather greater performance. The double capillary overlap requires only a one rib lap. This increases the cover sheet size and speeds up installation time, providing for a cost effective roofing and cladding solution.

Metalcraft fabricates the Kāhu sheets from steel manufactured by New Zealand Steel. This steel is supplied with different protective coatings which are designed to withstand conditions in specific New Zealand Corrosion Zones. 

Key Features
  • Double capillary overlap to the side lap:
    • Greater weather performance
    • Requires only a single rib lab increases cover sheet size
  • Suitable for roofing, and horizontal or vertical cladding 
  • Ideal for low pitch roofs (min 3°)
  • Kāhu sheets are available in Colorsteel® Endura®, Galvsteel®, Colorsteel® Maxx®, and Zincalume®
  • Kāhu sheets are available in the following sizes:
    • Thicknesses: 0.4mm and 0.55mm
    • Width: Cover = 875mm Sheet = 950mm
Scope of Use

Metalcraft Roofing supply the Kāhu® system as a horizontal and vertical external wall cladding, and for roofs with a defined minimum pitch of 3 degrees for use on commercial and residential buildings within the following scope:

Location:

  • In wind zones:
    • Up to and including Extra High as defined by NZS-3604:2011
    • Subject to specific engineering, if the engineer has satisfied themselves that the product, pitch and fixings will meet the conditions
  • In all climate zones as defined by NZS-3604:2011, subject to the limitations set out below
  • On buildings located within 1m of the relevant boundary, in respect of fire spread only

Building;

  • On new buildings that have been designed and constructed to comply with the NZ Building Code (NZBC) using timber or steel framing
  • On existing buildings using timber and steel framing where the designer and installer have satisfied themselves that the building is suitable for the intended building work
  • In conjunction with a vapour permeable building wrap that has a permeability of 36g/m2/day of a vapour resistance of no more than 500MNs/g
  • Can be used in conjunction with a potable water collection system
Limitations on Use

Location:

  • Kāhu® may be used as a roof cladding system in exposure zones B, C & D as defined in Sec 4, NZS3604:2011. For use in 'Microclimatic considerations', (as defined in Sec 4.2.4) refer to  Metalcraft Roofing
  • Kahu® may be used as a wall cladding system in exposure zones B & C. Where Kāhu is to be used in exposure Zone D, then only Colorsteel® Endura® or Colorsteel® Maxx® may be used

Building:

  • Where Kāhu® is used in an insulated building in conjunction with steel framing, a thermal break is required
  • Contact with other materials must be in accordance with Table 21 (E2/AS1), or compatible with the The New Zealand Metal Roofing Manufacturers Association Inc (NZMRM) Code Of Practice
  • Building height and design wind speed is limited by the Kāhu® design load span tables
  • Where it is used as a roof cladding system, Kāhu® sheet lengths of ≤40m must be installed on a roof with a minimum pitch of 3°. Kāhu sheet lengths of >40m but ≤60m must be installed on a roof with a minimum pitch of 4°
  • When installed vertically as a wall cladding, Kāhu® may be direct-fixed up to a risk score of 12 when risk calculation relies on the E2/AS1 risk matrix methodology
  • When installed horizontally or vertically as a wall cladding, Kāhu® must always be installed in conjunction with a drained cavity
3° Minimum Roof Pitch Required
NZS 3604 Corrosion Zone D suitable
Corrosion Exposure Zone D
NZS 3604 Wind Zone Extra High suitable
Extra High Wind Zone
NZS 3604 Wind Zone Specific Design suitable
Specific Design Wind Zone
Statement of Building Code Compliance

If designed, installed and maintained in accordance with all Metalcraft Roofing requirements, the Kāhu® Roofing and External Cladding system will comply with or contribute to compliance  with the following provisions of the New Zealand Building Code:

  • B1 Structure: B1.3.1, B1.3.2, B1.3.3 (a, b, c, d, g, i)
  • B2 Durability: B2.3.1 (b)
  • C3 Fire Affecting Areas Beyond the Fire Source: C3.4(a), C3.5, C3.7 (a)
  • E2 External Moisture: E2.3.1, E2.3.2, E2.3.7 (a-c)
  • F2 Hazardous Building Materials: F2.3.1

See product technical statement for full information.

Other Performance Attributes
  • Kāhu® Roofing and External Cladding system will not contaminate potable water — AS/NZS 4020:2005
B1 Structure compliant
Structure
B2 Durability compliant
Durability
C Protection from Fire compliant
Protection from Fire
E2 External Moisture compliant
External Moisture
F2 Hazardous Building Materials compliant
Hazardous Building Materials
Documents
CAD/PDF Link
Product Technical Statement
Loadspan Graph and Fixing Table
Fire Testing Document
Environmental Category Brochure
Colour Range
Additional Information
CAD/PDF Details
Commercial Horizontal Cladding Details
Commercial Horizontal Cladding Details DWG
Commercial Horizontal Cladding Details DXF
Commercial Roof Details
Commercial Roof Details DWG
Commercial Roof Details DXF
Commercial Vertical Cladding Details
Commercial Vertical Cladding Details DWG
Commercial Vertical Cladding Details DXF
Residential Horizontal Cladding Details
Residential Horizontal Cladding Details DWG
Residential Horizontal Cladding Details DXF
Residential Roof Details
Residential Roof Details DWG
Residential Roof Details DXF
Residential Vertical Cladding
Residential Vertical Cladding Details DWG
Residential Vertical Cladding Details DXF
BIM
Commercial Horizontal Cladding Details RVT
Commercial Roof Details RVT
Commercial Vertical Cladding Details RVT
Residential Horizontal Cladding Details RVT
Residential Roof Details RVT
Residential Vertical Cladding Details RVT

Metalcraft Roofing are a privately owned building product rollformer and installer with an extensive range of longrun roofing profiles, lightweight metal tiles and rainwater system solutions.

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