Remediation details: wall claddings - replacement

Installing new cladding over a cavity following E2/AS1

For buildings within the scope of the current version E2/AS1, installing a cladding covered by E2/AS1 and following the details given in the Acceptable Solution gives the following benefits:

  • The full extent of the framing damage can be ascertained and remedied.
  • The BCA will accept the cladding for consenting and Code compliance.
  • Window and door openings can be prepared with flexible flashing tapes, which may not have been used in the original construction. If windows are being reinstalled, they will need to have a packer added to the reveal or the reveal replaced to accommodate the thicker wall.
  • Stop-ends can be added to raked apron flashings.
  • Design parameters are given for the cavity, flashings and so on.
  • The cavity provides an added level of weathertightness safety for the owner.

With this option:

  • cladding details as published in the current version of E2/AS1 must be followed
  • windows will need to be removed and either stored, refurbished (if required) and reinstalled or replaced – the BCA may require a producer statement to certify the continued performance of the windows when reinstalled (also see remediation details: windows)
  • new head flashings will be required at openings to accommodate the cavity
  • designers will need to check that the installation of new cladding over a drained cavity does not infringe on requirements for side yards and fire separations between stand-alone dwellings under Building Code clause C Protection from fire (the installation will reduce side yard dimensions and clearances between the face of the wall and the boundary, which may be considered a contravention of requirements)
  • balcony walls and their junctions can be designed to meet E2/AS1 Amendment 5 details, for example, set-downs and saddle flashings
  • minimum cladding-to-ground clearances will need to be achieved
  • aspects of construction may still need to be approved as an alternative method to allow for details that are required but not in the current version E2/AS1 (such as a junction between two claddings).

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Installing new cladding over a cavity not following E2/AS1

There are a number of cladding options and details that utilise a cavity but may not be covered under the current version of E2/AS1.

Details and descriptions of the proposed cladding will need to be submitted to the BCA for consent as an alternative method (see building consent applications).

Specific details or specification clauses will be required covering:

  • fixing of the cladding to the cavity battens
  • window and door details including treatment of the framing
  • cavity drainage and closures
  • penetrations through the cladding
  • internal and external corners
  • top of wall
  • maintenance.

A number of these cladding systems have been independently appraised and, if installed in accordance with the BRANZ Appraisal, are considered able to meet the requirements of clause E2.

Systems covered by a BRANZ Appraisal include:

  • weatherboards – fibre-cement bevel-back; aluminium; uPVC; wood fibre; splay cut, rusticated, bevel-back and vertical shiplap timber
  • sheet claddings – wood fibre; fibre-cement with expressed joints; aluminium composite; corrugate profile metal
  • other – plastered brick; natural stone veneers; vertical shiplap.

With this option:

  • windows will need to be removed and either stored, refurbished (if required) and reinstalled or replaced – the BCA may require a producer statement to certify the continued performance of the windows when reinstalled (also see remediation details: windows)
  • new head flashings will be required at openings to accommodate the cavity
  • designers will need to check that the installation of new cladding over a drained cavity does not infringe on RMA requirements for side yards and fire separations between stand-alone dwellings under Building Code clause C Protection from fire (the installation will reduce side yard dimensions and clearances between the face of the wall and the boundary, which may be considered a contravention of requirements)
  • details will be required for balcony walls and their junctions
  • minimum cladding-to-ground clearances will need to be achieved.

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Installing new direct-fixed cladding following E2/AS1

Where the building is considered low risk and has a risk score under 7 for a limited number of sheet claddings and rusticated weatherboards and under 13 for bevel-back timber weatherboard), the faulty cladding may be removed and replaced with a new direct-fixed system under the current version of E2/AS1.

With this option:

  • the design is following the current version of E2/AS1 so the BCA must issue a consent
  • timber framing must be treated to at least H1.2
  • the remediated building does not have the added protection of a drained and vented cavity
  • windows will need to be removed to allow the opening to be prepared and a sill tray flashing installed in accordance with E2/AS1 Third Edition (windows in good condition will be able to be repaired and reinstalled, but new reveals or packers may be required where a different cladding is used – also see remediation details: windows)
  • existing flashings may be able to be reused – however, a cladding change from flat sheet to bevel-back weatherboard will require new flashings to suit the cladding dimensions.

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Installing new direct-fixed cladding not following E2/AS1

As with non-E2/AS1 cavity systems, these repair options will need to be submitted to the BCA for consent as an alternative method together with:

  • alternative method  details clearly identified
  • supporting information on the performance of the solution including the level of treatment of the existing framing – a minimum of H1.2 to meet the requirements of NZS 3602
  • identification of the compliance path being followed (see building consent applications).

Direct-fixed systems outside of E2/AS1 covered by a BRANZ Appraisal include (at the time of publication):

  • weatherboards – fibre-cement bevel-backed; uPVC; wood fibre; vertical and horizontal aluminium; rusticated and bevel-backed timber
  • wood fibre sheets.

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Specifying a different cladding to original

Where it is the owner’s wish to reclad the building with a different style of cladding, this can readily be incorporated into a reclad.

If the building is low enough risk that it could have been reclad with the same material direct-fixed but the owner requires a cladding change, then this may be argued to be betterment (if the cost of the cladding is greater). Adding a cavity where direct-fix is permitted for the cladding type under the current version of E2/AS1 may also be a legal issue that may be argued to be betterment.

Designers need to decide:

  • whether if E2/AS1 current version details can be applied
  • whether a cavity is required under the current edition of E2/AS1 for the building weathertightness risk score or it is a ‘must have’ for the owner (BCAs cannot demand a cavity be installed where the design is following E2/AS1 and the use of direct-fixed cladding is permitted for the cladding type and building risk score)
  • whether window removal is likely to be required.

New cladding will be a different thickness, so it may be difficult to ensure weathertightness where a new cladding is fitted behind existing window flanges. Typically, windows will need to removed and remediated (see remediation details: windows) or replaced. One option that may be possible is to add facings to the wall window junction, which may allow the windows, if sound, to remain in place.

The cladding change will require details that cover:

  • new flashings to windows to suit the width of the cladding
  • termination at the top of the wall to a soffit or at a parapet or at the roof level
  • corner details
  • base of wall and cladding to round clearances
  • integration of the cladding with decks.

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Specifying a rigid wall underlay

Under E2/AS1, a rigid wall underlay must be provided within a wall construction. Typically, this is provided by the internal sheet linings but may also be provided by:

  • a flexible wall underlay meeting the air barrier requirements of Table 23 of E2/AS1
  • a rigid air barrier such as fibre-cement sheet or plywood with an overlaid flexible wall underlay

Specifying an externally installed rigid wall underlay:

  • can provide a temporary weatherskin, particularly where the product used is coated with a weather-resistant finish
  • avoids the need to plastic tape a flexible underlay or add another batten (to hold the insulation in place and prevent the underlay bowing into the cavity) when batten spacings exceed 450 mm
  • can be used to provide structural bracing, particularly where a sheet cladding has been removed.

Note that proprietary rigid air barriers are not covered by E2/AS1 and must be submitted for consent as an alternative method.

Updated: 20 June 2017