Leaky Homes Exposed 

New Zealand Building Code

The NZBC has strict performance requirements for the products used to construct buildings. Relevant here are those for durability (B2) and moisture (E2) (download these here.

Harditex must provide adequate resistance to penetration by, and the accumulation of, moisture from the outside, and dissipate construction moisture without permanent damage to building elements, for a minimum of 15 years subject to normal maintenance. 

The Harditex system, installed and maintained in accordance with the James Hardie Technical Information, allows moisture penetration and accumulation and is incapable of dissipating it safely to the outside. The result is decayed framing and mouldy walls.

The building code requires in B1.3.4 Due allowance shall be made for: (a) The consequences of failure. This means that some compensatory feature is required to prevent damage to building elements in the event that there is a failure.  It is not reasonable to expect that buildings would never leak, so Harditex was required to make due allowance for when this happened.  Obviously, it didn’t or there wouldn't have been the Class Action Lawsuit and thousands of leaky Harditex houses.

James Hardie Technical Information Edition 1996

Click here to download James Hardie’s technical information booklet which they distributed to architects, councils, builders and owners to assist/direct how its product shall be specified, handled, installed, finished and maintained.

The publication contained important maintenance information for homeowners and future owners.

James Hardie Technical Information claims the Harditex complies with the NZBC clauses above where clearly it does not.

James Hardie’s Instructions Are Defective:

They Did Not Specify Compliant Timber

The 1996 Harditex Technical Information failed to specify H3 treated framing.

New Zealand Standard NZS 3602:1995 Table 1B required H3 timber to be used for framing not protected from solar-driven moisture through absorbent cladding material exposed to the weather.

Extract Table 1B Page 24 NZS 3602:1995

Harditex is absorbent and subject to solar-driven moisture. Therefore, according to the standard in force from 1995, it should only be used in conjunction with H3 framing. H3 framing was CCA treated and is highly decay-resistant. No house built with H3 treated timber would rot. 

Although NZ Standards are not compulsory, they are considered the ‘minimum consumer protection’. By instructing the use of a ‘lesser treatment’ Harditex was not offering the minimum protections. If the timber is then not durable enough, James Hardie is liable for the resulting damage, unless they were providing some other feature or protection to compensate for the loss of treatment.

James Hardie’s Technical Information specified that ‘kiln dried’ timber must be used for in many specific circumstances.  The only kiln-dried timber readily available up until 1996 was H1 (only suitable to resist insect attack and only when dry). From 1996 to 2004, Untreated Kiln Dried (UTKD) was also available and used extensively under Harditex.

Kiln-dried H1 has most of the boron driven out during the drying process or was a dry methanol boron infusion (later found to increase decay growth).  This was far less resistant to decay than the wet frame H1 boron treated timber also available. Of greater relevance though, is that H1 was never suitable in the first place.

The Harditex Technical Information incorrectly referenced obsolete standard NZS 3602:1990, which did not include this specific requirement for H3 timber, but in 1990 specifically required H1 timber that had to be adequately ventilated (not included in the Harditex instructions) and protected by external walls. NZS 3602:1990 did not actually approve H1 behind external claddings.

Harditex Is An Absorbent Cladding

Harditex is an absorbent cladding material and requires a special design to combat water penetration, accumulation, and allow moisture to dissipate.

It absorbs moisture when the conditions are damper, then releases it again when the cladding is wetter than the surrounding materials or atmosphere.

This is clear from Page 4 of the Technical Information, advising that the moisture content of Harditex can vary from 6%MC (moisture content) in the summer to 14% in the winter and at saturation, the moisture content is 33%. 

This means that from winter to summer, without any leaks, a Harditex wall will give up nearly a litre of water per square metre.  In the right (or wrong) conditions, this condenses back into droplets of water.

If there was a leak, or Harditex was wicking in around the edges and baselines it can reach moisture saturation at 33%.  Now there is accumulated moisture of 1.7 litres to be dissipated. At a winter temperature of 10C, the air inside the wall can only suspend less than 10 grams of water per cubic metre. It can never get out, it migrates into the framing, which decays.

Harditex Is Subject To Solar Driven Moisture

Solar driven moisture was researched by BRANZ in 1990 (ref rp122) in fibre-reinforced cement shingles also made by James Hardie. It is moisture transfer through the shingles caused by solar heating of the rain-wetted cladding material. Changes in temperature create a vapour pressure differential driving moisture into the cladding. The moisture stored within the cladding moves inwards to wet the framing and insulation.  At night the air cools down and can no longer suspend as much water, so this condenses as free water. In a Harditex wall, the condensation mainly shows up at the interface of the cladding/framing, the coldest part, where the building paper is located.  If plastic building wraps were used, the problem is exacerbated.  Obviously leaks and capillary wicking from the ground compound this. This problem is common to claddings made of absorbent materials.

Clearly, Harditex since 1987 should have always required H3 framing and a cavity to manage this condensation issue. Certainly, from the date of publication of NZS 3602:1995, James Hardie had to require H3 (CCA) treated timber behind Harditex. This also applied to other James Hardie products such as Monotek, Titanboard and the rigid backing board Hardibacker, used behind stucco. 

Harditex Did Not Allow for Condensation as Required by NZ Standards

Control of condensation is required throughout the NZ Standards

NZS 3602:1990 requires that “all timber and wood-based products shall be so built into the structure that due allowance is made for the control of condensation so as to control to a reasonable degree decay, corrosion, mildew, distortion and disfigurement.”

This requirement is also stated in the earlier NZS 3602:1975.

The later NZS 3602:1995 includes “Recommendations, by manufacturers of absorbent cladding materials, to eliminate or control solar driven condensation should be followed……such that their recommendations will provide the timber structure with the appropriate durability performance required by this Standard”.  The Standard provided ‘for more information refer to BRANZ report 122 Solar-driven moisture transfer through absorbent roofing materials....similar problems observed in external wall cavities clad with absorbent materials.’ 

James Hardie's Instructions are deficient in that they did not provide recommendations for eliminating or controlling solar driven (or any) condensation. Decay and insect attacks can then occur in areas where the condensation results in higher moisture levels.

Specified Unventilated Installation in Contravention of NZ Standards

NZS 3602:1975 required wall ventilation whenever external cladding is fixed to the exterior of the framing (Sect 24.2.2.2)

NZS 3602:1990 requires that “all building materials shall be so built into the structure that they are provided with adequate ventilation”.

NZMP 3640:1992 Hazard Class H1 clearly states that this timber is used in “situations which are adequately ventilated and continuously protected from the weather by roofs or external walls”.

NZS 3602:1995 refers to NZMP 3640.

Harditex failed to provide a means of ventilation such that accumulated moisture (from any eventuality) could dissipate. Water has no escape path so cannot dry out. It remains accumulated and in breach of E2. The result is that the moisture content exceeds the allowable NZS 3602:1995 limit of 18% for UTKD and 24% for H1, and the BRANZ Appraisal 279A limit of 20% for both grades.  In these conditions, the wall is not compliant and timber decays. 

James Hardie’s instructions incorrectly:

• Directed builders to enclose the framing in contravention of NZ Standards

• Directed builders to use H1 and UTKD in contravention of NZ Standards and Acceptable Solutions

• Failed to include instructions on how builders should compensate for the loss of ventilation and durable framing

By ignoring NZ Standards, and providing no mitigation, James Hardie exposed the owners of homes clad in Harditex to uncontrolled penetration of moisture and decay of timber. But for Harditex correctly following these standards owners may still have leaks, but the framing would remain durable without damage and the accumulated moisture could escape, perhaps.

Impossible Maintenance Requirements

The New Zealand Building Code requires that the durability periods are met with normal maintenance.  It is up to the manufactures to define that maintenance.

Page 13 describes routine maintenance to the various jointing and coating systems to ensure water ingress is prevented over the life of the building. It mentions maintenance may be required to PVC flashings and jointers, inseal and butynol strips, sealants, coatings and any cracks at joints It fails to state how an owner or inspector will know whether the Harditex has allowed the accumulation of water into the framing and if it has, how is an owner expected to remove it?

Traditionally, owners have discovered the need for maintenance when they see obvious signs, such as cracks, wet carpet, swollen skirting boards, decay and mould etc. That was back when framing had high levels of boron treatment which resisting decay. Owners had time to discover leaks, carry out maintenance and the framing would dry without decay. 

Harditex, with H1 and UTKD timber, without a cavity has little or no chance of staying undecayed until the obvious signs of leaks have already emerged. By then it’s all too late. The framing is damaged. Installing a moisture monitoring system would warn of wet framing before visible signs but even this may be too late for some wet walls.

Demanded Impossible Perfection

In order for Harditex to not damage the external wall framing it needs to manage the moisture content of the framing to remain below 18%MC throughout the life of the building.

For James Hardie to sell Harditex without a cavity and without specifying adequately treated timber, builders had to be able to construct the house, then owners maintain the house so that target is achieved, otherwise, insect attack and decay would occur.

Harditex also requires every single part of the external weathertightness envelope to remain weathertight.  Every single part of the construction process, designer to owner must be 100% perfect for 100% of houses.

This means for James Hardie’s overall Technical Instructions concept to work:

• Every sheet joint must be fully supported by framing, correctly fastened to keep it from moving, sealed on the rear surface to stop water absorption, be jointed correctly, painted correctly and maintained perfectly
• Every construction detail had to be capable of meeting this requirement above
• Every window must be installed perfectly, and not leak and perform better than the window BRANZ tested in 1986 (showed that all windows leak)
• Owners would be able to recognise when windows required servicing and were given processes to restore window flashings to be weathertight, and instructions on how to dry wet framing out
• Ensure other manufacturer’s products could not let water in behind the cladding.  The  Taylor Fascia  guttering popular at the time, overflows back across the soffits and into the walls behind the Harditex
• Ensure all window mitres were 100% perfect from manufacturers. BRANZ found around 10% of newly constructed windows leaked in a survey in 2002.
• Every penetration would have to be in place, not allow capillary or vapour diffusion and stay maintained
• Every owner and subsequent owners would need to have instructions that ground lines would need to remain clear (no building up gardens against the walls)  so Harditex baselines could not wick up to the framing for the life of the building
• Every subfloor space enclosed by Harditex would either need to stay below 18%MC,or the back of the Harditex would need to be painted (waterproofed) so the dampness couldn’t be transferred upwards.

That level of permanent perfection is unachievable in the real world.  In the past, with well treated, ventilated framing, no-one had to worry too much about defects, or lack of maintenance, or high ground lines and vegetation shading walls, or window flashings, cracks and poor paint because it didn’t matter. The framing remained durable. Now any of these things became terminal for the house because James Hardie decided it could promote Harditex over untreated timber without a cavity.

But There Was a BRANZ Appraisal for Harditex, with No Cavity and Untreated Timber

It remains a mystery why BRANZ Appraised Harditex face-fixed (no ventilation) over H1 and UTKD framing, eight years after Harditex was launched.  Maybe someone from BRANZ can explain this for all of us?

It’s irreconcilable how or why BRANZ did this.  They sat on the Standard Committees writing the standards requiring ventilation and treatment. They conducted research showing all windows leaked, and that framing should never be enclosed. They had a study showing that even well-treated timber in 30-year-old stucco houses was decaying badly (see Good Stucco Guide 1996, BRANZ).

A BRANZ Appraisal however does not offer James Hardie a reasonable defence for issuing negligent instructions that contravened NZ Standards.

James Hardie's $200 Million Dollar Gamble

James Hardie took a massive gamble and it has paid off - so far.

They persisted with selling Harditex, knowing that H3 was required, yet continued to specify H1 and UTKD.  They knew that ventilation was required but continued to specify no cavity.  They knew that houses leak including knowledge of multiple reported leaks in Harditex houses.  They knew that what they wrote and specified was not going to work for many houses.   James Hardie had been manufacturing sheet cladding since the 1930’s, and had complete knowledge of all standards.  They could not claim ignorance.

James Hardie balanced their risk of claims against not being able sell any product if they correctly specified ventilation cavities and H3 treated timber.  In doing so, they disregarded the impact this would have on tens of thousands of homeowners.   

James Hardie knew from early in the 1990’s that there were numerous failures and did not change their product or substantially alter their defective instructions.  James Hardie has already had to settle a number of private claims as well as a very significant one with the Department of Education. 

It looks like they dodged a big bullet in the recent James Hardy Class Action Claim.  Partway through the case, the funder Habour Litigation pulled the pin and backed out of the case.  Make no mistake.  This is no reflection on whether Harditex was fit for purpose, or whether the case had merit.  This was a commercial decision where a commercially driven enterprise decided that the likely return on their investment did not justify continuing.  Maybe they lost faith in their legal team or realised that even if they won, Jame Hardie would just run appeal after appeal, meaning that the payday was too far away.  That's what you can do when you have deep enough pockets.

A very sad outcome for the hopeful homeowners but not particularly surprising.  Harbour Litigation also pulled out of the Class Action against another cladding product 'Shadowclad'.

One of the last chances for holding James Hardie to account is the Parker and Associates Class Action.  This one is being privately funded by homeowners who must surely be concerned by the latest case.  We hope that they hold firm, and that Dan Parker does a better job of running the case than Adina Thorn did with her team.