More than just remediating

This Issue This is a part of the Weathertightness feature

By - , Build 119

When undertaking the weathertightness remediation of a building, there is usually the opportunity for betterment.

Figure 2: An example of typical appearance and form changes.
Figure 1: The original on the left and as remediated on the right with a different cladding and with risk features such as the pergola and the curved-top window removed.

Taking the opportunity during remediation to assess the existing building to see where its performance can be enhanced is defined as betterment. This work is typically additional to that required to address the weathertightness issues of the building. The owner may elect to carry out alterations to the building to improve the performance or alter the appearance of the building.

Opportunities to improve

When undertaking a remediation design, discuss with the building owner the opportunities that are available and the costs involved to:

  • lower the weathertightness risk of the building beyond that considered to be the minimum acceptable
  • consider other improvements to the performance of the building, such as bringing insulation levels up to current minimums
  • address defects (other than weathertightness) identified in the original construction
  • change the appearance of the building
  • remedy poor quality (original) finishing
  • improve the level of amenity, for example, adding a room or ensuite, remodelling a bathroom or kitchen
  • repair leaks in internal wet areas
  • incorporating sustainable features.

These options will need to be costed separately as they are typically considered additional to the work needed to make the building weathertight.

Remediation can impact on performance

For some remediation projects, the actual remediation work proposed will trigger a need to upgrade an aspect of building performance that must be included as a direct remediation cost.

One example is where a direct-fixed EIFS cladding is replaced by EIFS, or another cladding, installed on a cavity. The contribution of the cladding to the thermal performance is reduced and the insulation within the framing must be upgraded to compensate so that, when finished, the original performance is maintained – a statutory requirement that the performance (thermally) of the repaired building is no worse than the original.

Figure 1: The original on the left and as remediated on the right with a different cladding and with risk features such as the pergola and the curved-top window removed.

Go beyond the minimum

For lowering weathertightness risk, options may include:

  • adding a drained and vented cavity where E2/AS1 Third Edition and the level of timber treatment of the wall framing allows the use of a direct-fixed cladding to a low-risk building (for example, a monolithic cladding can be direct-fixed at risk scores of up to six and a bevel-backed weatherboard can be direct-fixed for risk scores of up to 12)
  • roofing over or building in waterproof decks provided this can be accommodated within current RMA requirements
  • removing cantilevered membrane covered waterproof decks completely – an option may be to construct a new deck that is separated from the building envelope
  • a change to the cladding type, for example, from a monolithic finish to a bevel-backed weatherboard (see Figure 1)
  • removal of parapets
  • simplifying complex multi-pitch roofs
  • repitching a flat roof with a change of roof cladding
  • adding eaves or verandas to protect the wall surfaces from wetting and lower the risk score
  • removing pergolas and other structures attached to the building through the cladding
  • replacing windows with raked and curved window heads (or sills)
  • removing a parapet so a roof can drain to an external, rather than internal, gutter
  • lowering the finished level of waterproof decks to below the adjacent floor level or incorporating drainage adjacent to the wall of the building.

When considering design changes to lower weather tightness risk, designers need to confirm:

  • that the changes to the shape and form of the building are permitted under the district plan, preferably without the need for notifiable planning permission
  • the structure of the building can accommodate the new construction
  • changes address the weathertightness issues with the building and future risk is lowered
  • a Code Compliance Certificate will be forthcoming if such work is built as consented
  • the client understands the changes and the impact they will have.

Improving building performance and amenity

Other improvements that may be economical and feasible, particularly where claddings are being removed, may include:

  • bringing insulation levels up to current minimums (or better) because the wall framing has been exposed – where timber damage has occurred, it is likely that the insulation will need to be removed and replaced anyway
  • replacing single glazing with double glazing
  • replacing basic aluminium joinery (for example, without condensation drains) with higher specification joinery
  • replacing existing aluminium joinery with thermally broken aluminium or uPVC units to improve the thermal performance of the windows
  • repairing leaky bathrooms, particularly tiled showers
  • in older houses, the replacement or replanning of ‘tired’ kitchens and bathrooms
  • incorporating a rigid air barrier where none was required originally
  • using framing with a higher level of preservative treatment than that required by NZS 3602:2003 Timber and wood-based products for use in building
  • improving the drainage of surface water from around the building.

Incorporating sustainability

During a remediation project, designers, owners and contractors have the opportunity to incorporate a number of sustainable features into the design and construction practices, such as:

  • upgrading wall and window insulation values to reduce heat loss and reduce energy demand
  • considering the whole-of-life cost rather than the initial cost when discussing cladding selection
  • selecting materials that require less maintenance
  • selecting materials that can be recycled at the end of their serviceable life
  • minimising waste generation on site
  • reusing or recycling materials where feasible
  • replacing open downlights with CA-rated units
  • reducing the use of solvents through paint and timber treatment specification.

Appearance changes

One aim with appearance changes is to move away from some of the stigma attributed to monolithic claddings by changing the cladding being used, for example, using weatherboard instead of a plaster type finish. Appearance changes that incur additional costs are likely to be contested in any leaky home dispute.

Figure 2: An example of typical appearance and form changes.

Other changes that can impact on the original appearance (and can lower weathertightness risk) include:

  • removing parapets
  • adding roofs over decks
  • removing cantilevered decks
  • removing or replacing windows with curved and raked heads
  • removing pergolas and other features installed with penetrations through the cladding
  • removing internal gutters and installing them externally
  • repitching low-slope roofs to improve drainage
  • modifying reverse slope eaves.

There is the opportunity during remediation design – particularly where a full reclad is warranted – to redesign or design out the risk associated with these features (see Figure 2).

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Articles are correct at the time of publication but may have since become outdated.

Figure 2: An example of typical appearance and form changes.
Figure 1: The original on the left and as remediated on the right with a different cladding and with risk features such as the pergola and the curved-top window removed.

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