Product Product RotStop (Framing) (Treatment)Protects framing from insect attack and decay
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Item About RotStop Folder
RotStop Framing Treatment for Houses (effective 1 May 2022)

Purpose of RotStop: RotStop protects vulnerable framing from decay and insect attack

Reason to RotStop: All homes have roofs, gutters, walls, windows, doors and ground lines. Despite efforts details leak, timber framing gets wet and decays unless it is treated. You may not even be aware these threats are part of the risk of owning a home. We have known homes leak ever since humans wanted shelter and protection. But recent construction methods could mean your home could have been built with H1 or UTKD timber framing which is not suitable for external walls as it is not treated to protect against decay if and when it gets wet.

Houses that leak have been labelled ‘leaky buildings’ but the reality is all homes leak, it’s just homes built with H1 and UTKD framing are susceptible to decay. We all know and accept leaks are inevitable. Homes are not and never will be 100% leak free. Spend what you like, maintain however you want, fact is somewhere, sometime, it will leak. If the framing was treated against decay, you would still have wet framing, but you would not have a building suffering from decay that may need expensive repairs or require a reclad or pulled down. Not so with homes built with H1 and UTKD. These may require substantial repairs if and when the leaks occur.

Background why RotStop is required: RotStop is required treat  the wall framing in your home to provide consumer protection for those buildings loosely described as leaky buildings, built between 1992 and 2005 using H1 and UTKD timber framing that decays when details leak and wets the framing.

This is not a new problem: We go back to the 1952 Government Boron Inquiry. State Advances, tasked by the then Labour Government to build 100,000 homes struck serious problems in the late 40’s. The homes they financed and certified became damaged by decay and borer. Rimu stocks were required to earn export dollars so in came Tawa, Kahikatea and Radiata pine to frame our precious assets. Rimu is durable, the others perishable, and that is what happened. Same defects in homes but now the perishable framing perished.

According to records, State Advances said owners could not afford the cost to repair homes built using perishable timber. Homes leaked; framing rotted. In response State Advances took the reasonable decision and mandated tanalith treatment to protect future owners from framing rotting. Every decision has a consequence. The problem was the timber industry was not equipped for wholesale production of tanalith framing to meet the 100,000 homes needed. Only a handful of mills had the capacity and equipment. The purpose of the 1952 Boron Inquiry was to determine if an alternative treatment, based on Boron, could provide similar consumer protection and be safely used as a substitute to tanalising. The Inquiry found it could so approved ‘Boron’ as a timber treatment for housing on the basis the Boron retention was sufficient to control all wood destroying pests. Boron could only be sold as a treatment if it protected external roof and wall framing from borer, decay and termites. The boron strength the Inquiry set to achieve this was 1.2% Boric Acid Equivalent (BAE). That equates to 1.2kg boric acid/100kg of timber. Boron comes from Borate, a hydrate salt of boric acid. A bit like table salt.

For 40 years owners were protected by the State. Framing did not rot, not easily. So, what happened? Instead of looking at the historical benefit of Boron, the regulators including directives from the State, allowed H1 framing in 1992. H1 has only 0.1%BAE and comes with a limited Hazard Classification for the control of borer. Not decay. Boron could be substituted with permethrin. Neither control decay.

How could this possibly happen? A closer read of the Standards shows it shouldn’t have. The 1992 New Zealand Standard MP3640:1992 applicable at the time states
9.1 Hazard Class H1
9.1.1 Where timber, including plywood, is used out of contact with the ground and in situations which are adequately ventilated and continuously protected from the weather by roofs or external walls. The primary risk to timber in this situation is from attack by wood-boring beetles such as Anobium and Lyctus

What the Standard is clear about is H1 framing cannot be part of the external wall. H1 must be protected by the external wall. Despite this H1 was approved by Councils and signed off in CCC in houses built entirely out of H1. Roofs, walls, subfloors, decks, showers, everywhere. All external and internal walls.

The outcome is consumer law has been trampled on. Promoting and selling products complying with a Standard are deemed as fit for purpose. Suppliers can sell higher treated timber as that provides even greater protection. But if they sell or promote framing with a lesser treatment, i.e., less than required by the Standard, and it becomes adversely affected, they are breaching consumer protection law. This is something lawyers have failed to bring to the Court’s attention. Judges would have been able to determine responsibility differently. But it hasn’t.

The Clarke Labour Government instead delivered the Weathertight Homes Resolution Service in 2002 specifically to blame the builders for the leaks, that caused the H1 to rot, despite the fact H1 was never approved in the NZ Standards for external wall framing. H1 and UTKD are not fit for purpose to be used in external walls or where framing may become wet for any reason.

MP3640:1992 specified H2 as the correct Hazard Class for framing external walls. H2 was never used. H2 approved tanalith or LOSP Tin, but not boron. Tanalith and LOSP Tin don't leach. Boron does.

But it gets worse. New Zealand Standard NZS3602:1995 Table 1D became the entry point for untreated kiln dried framing (UTKD) in 1995. Under this Standard UTKD is approved as a substitute for H1. But H1 was never approved as framing for external walls. That means UTKD cannot be used either. But Councils went ahead and approved it and issued CCC. Now we have completely untreated timber in external walls that get wet. The CCC should never have been issued. Consumers are not protected.

The building code requires homes to be constructed in a way moisture cannot cause damage. This is clause E2 External Moisture
E2.1 The objective of this provision is to safeguard people from illness or injury which could result from external moisture entering the building.
E2.3.2 Roofs and exterior walls shall prevent the penetration of water that could cause undue dampness, or damage to building elements.
The Judge in the recent Court case MOE v Hawkins has finally determined the word ‘could’ is operative in that if something ‘could’ leak means it cannot be compliant with E2. But we know all homes not only 'could' leak but 'do' leak.

BRANZ tested windows in 1986 and found all attempts to stop leaks failed.

BRANZ Accredited Advisors reported thousands of leaks in houses they inspected from 1992 on. Every owner knows roofs, walls and showers always find ways to leak. The net result is prior to 1992 so what, the timber is protected against rot, but after 1992 with H1 and UTKD it’s a disaster. H1 and UTKD will not be durable for the life of the building. H1 and UTKD framed homes need some form of intervention to prevent decay.

Standards are periodically changed over time when consumer protection is less than acceptable. Industry groups can make submissions to seek modifications or changes. These must improve consumer protection, not make things worse. Carters presented a 5-volume submission to NZS3602:1995 to re-introduce UTKD. The preface includes this statement:

The investigation is confined to protected timber in dry interior situations not related to ground contact.
Timber in ‘dry interior situations’ dates back to the 1950’s Standards and relates to non-load bearing internal walls which were still treated to 1.2%BAE. In 1995 interior framing had a 15-year minimum durability in B2. The limitation sought for use in ‘dry interior situations’ has the same meaning as H1 ‘protected by external walls’. Interior walls are protected by external walls. What Carters were saying is consumers would still be protected because dry interior walls would never get wet.

Even if Carters submission was 100% correct in every context UTKD should never have got a status in the Standard as it would get wet at construction, or floods, or when plumbing aged and broke. 

Table 1D in NZS 3602:1995 heading should have stated ‘for use in dry interior walls’ as Carters submission requested. It didn’t. NZ Standards mistake.

Councils allowed Table 1D in NZS 3602:1995 as the entry point for UTKD framing everywhere. Internal and external. This is a screw up of a magnitude never before seen in New Zealand’s history.
Every home since 1992 has perishable framing on external walls and framing that could get wet. The 1952 Boron Inquiry rejected kiln dried timber as this was reversible when the framing got wet. It is useless when wet as it offers no consumer protection. The Inquiry rejected Boron unless it was strong enough to control all wood destroying pests. It needed regular top ups of boron. The consumer protections homeowners enjoyed for 40 years are now gone.
H1 and UTKD are not compliant to B2 as external walls are required to have a minimum durability of 50 years. The framing is concealed and hidden from inspection so must remain durable in all conditions including expected leaks.
This sets the stage for the worst financial disaster of your lifetime. Buildings leak when it’s raining. NZ is a high rainfall country. So, buildings with framing with no treatment offer no consumer protection. Things could not get worse. The walls do leak. BRANZ knew and took no action.

BRANZ submitted to Government in 2002 that it had done weathertightness testing of windows in 1986 and failed to find a way to prevent leakage. Nothing worked 100%. Windows needed wider flanges and undersill trays. Even then they leaked. In 1986 leaky windows were a ‘so what we have treated timber to prevent rot’. Ok. But the new framing H1 and UTKD around the same leaky windows decays. BRANZ have no solution. It's your problem to solve. None of the regulators even want to talk about this.
The Hunn report in 2002 was scathing of BRANZ for failing to test windows yet issued appraisals for cladding systems using H1 and UTKD framing in external wall framing. BRANZ then began official weathertightness testing to the 1992 verification method and failed all cladding and window systems, unless they were on a cavity and used H1.2 treated timber. These changes were not fully implemented until 2005/2006. None of this has been reported to you as owners. If it had, you would have wised up and laid massive claims against BRANZ for appraising H1, UTKD for external walls and claddings with window flashings they failed to test and when they did, found them to be defective. No chance any of this meets compliance. No chance of any defence.
And worse still? The 1952 boron approval came with several requirements. Boron is a salt which becomes soluble when wet (in the form of boric acid). It can leach out and dissipate thus reducing its effectiveness against decay. Boron treated framing was approved in 1952 on the basis it always had ‘adequate ventilation’: achieved with a cavity batten, brick veneer, spacers, drill holes or sarking. Absorbent claddings that would ‘suck out the boron’ could not be fixed directly to boron treated framing. This is repeated in the 1992 standard for H1. Face fixed claddings that trap in water were never approved. Wet framing decays if not treated against decay. Yet Harditex and Stucco came with BRANZ Appraisals or were granted BIA Acceptable Solution status.
Both BRANZ and BIA were represented on the 1995 NZ Standard 3602:1995 Standards committee and approved Table 1B which requires absorbent claddings like Harditex and Stucco to have H3 treated timber as the external framing. H3 is Copper Chrome Arsenic (CCA) and highly protective of wetting, condensation and wicking. It does not leach out. The framing does not decay. Easily. This change to the Standards came following BRANZ reports from a cladding survey in 1994 on 30-year-old 1960 houses constructed with boron framing at 1.2%BAE. BRANZ reports these well treated homes had serious decay. The boron must have leached out to an extent it no longer offered protection against decay. Boron is useless when face fixed with absorbent claddings. But Hardies, BRANZ, Councils and BIA continued promoting H1 and UTKD everywhere without limitation. Your home should have been protected with H3 framing had BRANZ updated its appraisals and council read the Standard.
But windows are not the only problem causing leaks. Leaks are everywhere.
  • Taylor and Klass Fascia are not conventional external gutters. The gutter is concealed inside the Fascia on top of the soffit. In heavy rain, or defective installations, or as they age and rust, rainwater overflows onto soffits diverted into the wall framing wetting it and rotting H1 and UTKD.
  • Cladding trends buried plaster into the ground providing wicking mechanisms to wet framing.
  • Weathertightness complexity increased as architects pushed the boundaries of design and mixtures of claddings and multiple weathertightness details. Awards were issued to ridiculous designs now a nightmare for owners.
  • Flashings disappeared. These cost money and are hidden anyway.
  • House construction skills were lost when apprenticeships lost favour
  • Dozens of new untested products came onto the market without any history of use.
  • Decks became the norm.
  • Soffits disappeared so more houses could be built per hectare.
  • Window designs and shapes became complicated to win awards. None are properly flashed.
  • Roof underlays were found to sag directing water into walls
  • And a hundred more
The bad news does not go away. It’s become your legacy to deal with. No magic wand. Sorry.
The good news is your home (1992-2006) must be at least 16 to 30 years old and still standing. How come? Well done. Or lucky maybe. Or maybe you haven’t wanted to look? Maybe the damage is not yet terminal. Maybe it never will. Maybe it just needs a few tweaks to right the ship. You need to know. It's in your interest. Ignoring it is what the regulators want you to do.
Builders and councils are protected from prosecution if you don’t make a claim within 10 years and 15 years for suppliers selling something that is not fit for purpose.
You are out of time. Lawyers may form another view at some stage. Wishful thinking.
The good news: We need to go back to NZ Standard 1953 CP4 approval of Boron required regular maintenance to top up boron levels. The 1952 Boron Inquiry accepted boron dissipates and leaches, reducing its effectiveness. To restore consumer protection the 1953 Standard stipulated topping up with additional coats of boron provides ongoing protection against all wood destroying pests. This is called ‘normal maintenance’ for framing.
1953 Standard CP4 (page 14)
Maintenance (of boron treated framing)
Surface Treatment
9. Timber initially treated by surface applications of preservative should receive periodically a liberal coat of preservative of the same type, well worked into all joints and cracks. The frequency of such applications depends on conditions of service and would normally correspond to that of periodical external painting in the locality.
Good if the walls are not lined maybe? A little technical problem in the way? External walls generally have the framing sandwiched between the cladding and GIB? Not accessible to apply liberal coats of preservative with a paint brush! A bright idea is required. Topping the boron framing somehow is required for Boron framing to comply with B2.3.2. Not new, but ignored, your problem. But consider the building regulation B2.

B2.3 From the time a code compliance certificate is issued, building elements shall with only normal maintenance continue to satisfy the performances of this code for the lesser of; the specified intended life of the building, if any

Boron external wall framing to be compliant must be capable of being maintained by ‘normal maintenance’. Normal maintenance to a building is washing down and repainting. Nothing in there to meet the 1952 Boron Inquiry stipulated boron dissipates and CP4 regular top up coats required.  Current boron treatment systems do not ensure boron no longer leaches. But H1 and UTKD never had enough boron anyway. But it can be retrospectively added.  As in a way to maintain framing.

Step in RotStop. RotStop is designed to be injected into the wall cavities to retreat and top up the Boron. To protect the framing against decay. Obviously, no-one will ever be able to treat every lineal meter of framing throughout a building. Even if the cladding and roof was removed. Not possible. That was the job at the mill before the framing was cut up into framing. NZ Forrest Research Institute paper on Boron in 1994 was at $122 per home boron is a cheap once only insurance. Right on.

But not every lineal meter of external wall framing is subject to wetting.

Framing under generous soffits could never get wet unless your home has a Taylor or Klass Fascia. Framing above windows should not get wet as gravity pulls water down.

RotStop is targeted to the framing at risk and vulnerable to wetting.
Your home is likely 16-30 years old by now so it’s a matter of us finding out where the external framing has been at risk or wet. Time and history will tell us more accurately than a 30-minute weathertightness test at BRANZ ever will. Your home is the test bed we have to work with. We find how perished your framing is through extensive Invasive Tests. These provide timber samples below each of the weathertightness risk locations. If the framing is in good condition, then why panic. If the framing is decayed, then something needs to be done. If the framing is sort of in between, neither perfect nor decayed, RotStop steps in and kills the decay. Then attend to the cause of the wetting. Treated framing is no longer at threat of decay even if wet again. Invasive tests also provide moisture contents. These can vary between summer and winter. A previous owner may have tried to fix the leaks. The framing samples could be dry indicating the leak is fixed but the framing could be decayed as the H1 and UTKD offered no protection. Decay needs killing. Conversely the framing may still be wet, so the repair failed. Now it needs RotStop and repair.

Once treated with RotStop the framing won’t decay further which buys some time to complete solutions. These can be a range of repairs including introducing ventilation if needed, modifying window flashings, upgrading the Taylor Fascia and changing ground lines etc. Then ongoing monitoring of the Mdu Probes gives feedback of success and warns when future leaks are found so more repairs can be done before any further damage occurs. This is sound risk management.