Labour fails homeowners in timber treatment scam
Labour fails homeowners in timber treatment scam
National’s Building spokesman, Nick Smith, says Labour is allowing homes to be built of timber that does not meet its own new standard, even after the billion-dollar furore over leaking and rotten homes.
“Thousands of homeowners and builders are being duped into thinking they are using treated timber when, in fact, it has only been surface-sprayed.
“The new standard of timber treatment NZS 3640 was adopted in 2003 after the leaky homes crisis, and requires ‘complete sapwood penetration’ (188.8.131.52). But in April 2004 the Building Industry Authority approved a new surface boron-treated timber, code marked as T1.2, in breach of this new standard.
“This product is risky, in that 80% of the timber is left untreated, exposure to rainfall during construction will wash it off, and there is no protection from borer.
“Consumers got burnt in 1985 with the AAC timber treatment debacle and are now paying again for errors over the introduction of untreated kiln dried timber in 1995.
“The last thing homeowners need is another unproven, non-compliant timber product that puts their most important asset at risk.
“Labour and the BIA seem to have learnt nothing from the leaky homes debacle. They continue to arrogantly ignore the pleas of respected timber preservation and building experts about this flawed product.
“This T1.2 product needs urgent and independent reappraisal. We need to take a cautious approach to timber treatment after the debacles of the past two decades.
“This adds another chapter of incompetence to this Government’s response to the leaky homes crisis. They had a duty to ensure future homes would be built to a decent standard but have failed,” Dr Smith says
Declining Wood Durability Standards Threaten Home Owners & the Building Industry - Dr. Robin Wakeling, wood mycologist (021 87 87 17)
Due to the leaky building crisis a group of experts revised NZS3640:1992 in 2003 to ensure that durable framing is used in buildings. A traditional and proven framing system using boron (H1.2) is described in this standard (minimum durability level for exterior wall cavity framing). An essential component of compliance with the standard is full sapwood penetration by the boron (184.108.40.206). Thorough penetration is essential for robust durability because only treated wood is fully protected from fungal decay (rot) and insect borer,
In 2004 a product described as an “Alternative Solution” to H1.2 and as boron T1.2 was approved for use by the BIA (now DBH). This product fails to meet the penetration requirements of NZS3640:2003 that ensure adequate durability. Boron penetration for H1.2 framing is normally achieved by pressure impregnation of dry wood or by a controlled diffusion process requiring application of boron to freshly sawn wet wood. For the T1.2 product boron plus an orange dye is sprayed onto the surface of kiln dried framing. Other non-compliant systems apply boron to the surface of dry wood using a dip process.
Availability of framing products that do not comply with NZS3640:2003 has potentially serious consequences for consumers and the building industry.
For practical purposes NZS3640 became redundant with respect to H1.2 when the BIA approved spray-on boron treated framing as an “Alternative Solution”. The DBH is now considering a further “Alternative Solution” application for use of spray-on boron treated framing in a more severe hazard Class called H3.1, also specified for buildings. If this application is approved this will compromise another major component of NZS3640:2003 i.e. the H3.1 hazard class.
Without a standard with clear minimum requirements that the industry must comply with, the consumer cannot be guaranteed that products of adequate and proven durability will be used in buildings. Approval of “Alternative Solutions” by the BIA (DBH) has therefore compromised the durability standards of available framing at a time when vigilance and caution should be of particular importance i.e. during the leaky building crisis, the consequences of which will be present for another 10 years.
In Australasian and Pacific Rim countries, at least 5 years of durability testing is typically a basic requirement before approval of new wood products for situations containing a fungal decay and/or insect borer hazard. The accelerated test method used to test T1.2 boron treated framing prior to approval did not adequately simulate the diversity of in-service hazard conditions typically encountered and failed to test the more severe situations.
A vital component of recognised standard wood decay test methodology is exposure of a sub set of test material to a leaching/washoff regime. This vital step was omitted during pre-approval durability testing of T1.2 boron treated framing. This was a serious omission because boron salts are water soluble and do not fix to wood. Substantial boron loss from wood surfaces during exposure to rain is an inevitable consequence of normal building practice and could also occur during water ingress into leaky wall cavities. Boron loss is slow and controlled for H1.2 framing because the boron is distributed across the framing thickness as specified by NZS3640. This situation is not the case when the boron is sprayed onto the surface to produce non-compliant T1.2 boron treated framing i.e. the bulk of the boron is on or close to the surfaces in contact with depletion forces.
A unique study involving microscopy and preservative analysis of multiple wood samples from approximately 800 leaky buildings provided significant insight into the strengths and weaknesses of different framing products. It was clear that use of NZS3640:1992 compliant boron treated framing greatly reduced the incidence and severity of decay as compared with decay occurrence in untreated framing. However, it was apparent that the penetration requirement of NZS3640 and the associated slow boron loss was a major factor that had contributed to provision of durability. The implications of this information were presented to the BIA in October 2003 prior to approval of T1.2 boron treated framing but no response was forthcoming. This information was also presented at a Timber Preservation Council meeting in 2003 at which a senior representative of the producer of T1.2 boron treated framing did not refute the findings of this work.
In my professional opinion the approval of framing products that do not comply with NZS3640 is at best risky. At worst it may cause ongoing hardship to building owners and those affiliated with the building industry through premature decay (rot) of wood framing in leaky buildings. The legacy of practices that cause leaky buildings and which already cause great hardship necessitates use of durable framing of proven reliability for the foreseeable future. Spray-on boron treated framing is unproven in service and long term field trials normally considered essential have not been completed.
It is essentially predictable that surface application of wood preservatives is unlikely to provide wood products of sufficiently robust durability. The additional step of forcing preservative into the interior of framing may add cost but it is a very small and insignificant cost compared to the cost borne by the consumer when products fail in service. Durable wood has significant advantages over other building materials in terms of sustainability and performance in service. Failure to ensure use of adequately durable framing has eroded these advantages. A robust Government policy is needed to reverse this situation.
Q & A on Surface Sprayed Timber T1.2
Q1 How widespread is the use of the new T1.2 timber?
Approximately 50% of structural timber being used today is the T1.2 product. It is sold in all the major centres as an equivalent to H1.2 and at the same price. Many timber merchants contacted advised the products were identical. More than 10,000 homes have already been constructed using this product.
Q2 Why does the surface sprayed T1.2 timber contravene NZS3640:
NZS3640 is the New Zealand Standard “Chemical Preservation of round and sawn timber” and was updated in 2003 in the wake of the leaky homes crisis.
Clause 220.127.116.11 of the standard requires “complete sapwood penetration.”
The surface sprayed boron achieves only 3mm penetration. This means in a typical 4 x 2 (90mm x 45mm) timber only 20% of the timber by volume is treated.
Q3 What are the risks of the surface sprayed T1.2 timber?
Timber framing during construction is inevitably exposed to rainfall, which (because boron is soluble) will, in a major downpour, remove the boron preservative.
Timber is inevitably cut to size on site leaving key surfaces exposed. Moisture and rot commonly occurs at joints. The requirement that such surfaces be recoated by brush on site is unrealistic and, according to industry sources, does not happen.
Boron is treatment against rot and borer attack. Borer attacks at moisture contents less than at which boron migrates. This means the T1.2 does not provide protection against borer.
Where a leak occurs in-situ, the water arrives on the surface, and the boron is easily removed, leaving the timber untreated and vulnerable to rot and borer.
Q4 Why is the spray-on treatment preferred by some in the timber
T1.2 treatment is cheaper and quicker to process because it simply involves a spray on surface coat at the end of the sawmill process.
H1.2 treatment takes a significantly greater time and expense. The boron is added when the timber is green and typically 6-8 weeks allowed for diffusion. The alternative process is to dry the timber and then pressure-impregnate the boron in expensive pressure vessels.
Q5 Has anybody expressed concern to the Building Industry Authority (now
Department of Building and Housing) about the approval of surface treated
New Zealand Institute of Building Surveyors June ’04.
“This product in its accreditation with only a light covering of boron to the outer timber has been given the same status and standing as a fully core-penetrated treated product. This is obvious nonsense.”
- Mr Kevin Longman Chairman, NZIBS Letter to BIA 3.6.04
Prendos Building Consultants, May ’04.
“I am very concerned with the use of envelope treatment on timber, that is boron treatment, in any situation but remedial.”
“I ask you to revisit this matter. I believe that it is going to lead to future disaster.” Mr Greg O'Sullivan. Director, Prendos. Letter to John Ryan CEO BIA 27.5.04.
Dr Robin Wakeling, Research Scientist specialising in wood preservation.
“It is possible that if the product used in New Zealand dwellings that subsequently develop leaks, the level of framing durability may be inadequate to provide a reasonable window of opportunity to correct faults prior to serious wood deterioration damage.”
Letter to BIA October 2003 expressing serious concern about introduction of surface treated boron timber framing.
Q6 What response has the BIA made to concerns about the surface
treatment T1.2 product?
The BIA has not acknowledged or responded to the correspondence of Dr Robin Wakeling despite his holding a PhD specifically on rot in pinus radiata, 13 years experience as a research scientist, and his chairing of the International Research Group on Wood Preservation from 2002 – 2005.
In other responses, the BIA has “noted the concerns” and has stated: “the issue of leaching of preservative was considered by the appraiser and the Authority in its processing of the accreditation applications for the Timber Saver treated product. It is important to remember the product has been appraised for use in particular situations and subject to certain limitations, including limits on site exposure, all of which is described in the appraisal. The Authority is satisfied that in these situations the product will perform as claimed.”
The problem with this approach is that it repeats the error of untreated kiln dried timber that was approved on the basis that its moisture content never exceeded 20%. This was impractical and now thousands of homeowners are paying the price.
The appraisal requires “The treated timber will be protected from the weather” and “liberal brush application of Protim Framesaver needs to be applied to exposed surfaces to reinstate the treatment.” There is little evidence in practise of these conditions being met.
Q7 Why was the BIA process of approval of T1.2 timber unsatisfactory?
The timber was not accessed in terms of compliance with the code that requires full penetration.
There was no independent peer review for the testing methodology used.
The accelerated test approach has been relied upon only once before, and that was for the AAC treatment process that failed.
The test methodology is not internationally recognised and does not provide for a leaching regime as would occur in a leaky home.
The one test was done in 2001 prior to the public furore over leaky homes and the realisation of the scale of the failure of kiln dried untreated timber product.
Q8 How does New Zealand’s approach to timber treatment compare with that of Australia?
There are an increasing number of media reports in Sydney and Melbourne of problems with leaking rotten homes. The NSW Government announced on 22 March 2005 a doubling of the required minimum level of preservative in timber used for home construction under the NSW Timber Marketing Act. The surface treatment system is not permitted in Australia.
Q9 Why is surface-treated boron acceptable as a remedial product but not for new timber?
The only way timber can be treated in-situ is by a surface process. The only way timber can be fully submerged or pressure treated is to completely dismantle a home. These costs are so prohibitive that it makes sense to at least provide some protection by surface coating untreated timber in-situ when repairing and re-cladding leaky homes.
BRANZ has approved the use of surface treatment as a remedial measure but has expressed concern about its use as an alternate to full penetration treatment for new timber.
Q10 Isn’t the problem of the leaky homes caused by sub-standard buildings and leaks rather than timber treatment?
No. The use of untreated timber has made homes more vulnerable to rot from leaks. Most homes leak at some time during their life, and timber treatment provides protection by significantly slowing damage. Timber treatment is the ‘seat belt’ for a house, in that if leaks occur it minimises the damage. The project manager of a typical leaky home in Auckland facing a $300,000 repair bill said last week that the leaks could have been fixed for $10,000 had treated timber been used.