The popular misconception that ‘leaky buildings’ must be re-clad to stop the leaks is wrong and is being pushed by re-cladding companies and councils to suit their own agendas.  Many home-owners are unnecessarily spending a fortune, thinking that they don’t have a choice.

In this article, we discuss the mature alternative that leaves more money in the pocket of the homeowner and doesn’t subject them to the stress and disruption of re-cladding.


All Houses Leak – But That Doesn’t Mean “Re-Clad”

There have always been numerous places where water may leak into a building which why traditionally, houses were built with three layers of protection:

  • the framing was treated with boron to a level where the expected leaks did not cause damage,
  • external framing was required to be ventilated with cavities, so wet framing could dry out following leaks and repairs,
  • windows, doors, decks and penetrations had to have proper flashings to keep out the water.

A series of unfathomable decisions then led to a progressive reduction in building durability and weathertightness:

  • from 1992, houses had inadequate treatment protection to the framing and between 1998 and 2005 often had untreated external wall framing.
  • the requirement for ventilating timber in the New Zealand Standards was ignored, allowing direct fixing of cladding (no cavities), with no additional protection to compensate for the lack of drying.
  • consents and Certificates of Code Compliance were given to houses without cavities and without adequate flashings or adequate means of preventing leaks.

The result was wet, unprotected framing that stayed wet, then decayed….then the leaky homes scandal erupted.

Now all monolithic clad or plaster clad houses are tarred with the stigma that they might be leakers or rotting and that they should be worth less money.

A whole industry has emerged, promoting re-cladding as the solution when leaks or decay are found.

However not all external framing decays. Not all framing gets wet, and dry framing does not need a cavity as it is already dry. If walls are dry, then whatever flashings are in place are working.

It is 100% possible to make a plaster clad house just as dry and safe as any other house –  without spending hundreds of thousands of dollars on re-cladding.

It’s time to be sensible about our houses and start making decisions that stack up with the facts.


Why Do Re-Cladding Companies and Councils Want Houses Re-Clad?

 The answer to the first part is obvious.  These companies, and the consultants who refer homeowners to them are set up to promote re-cladding and this business is worth hundreds of millions of dollars.  They offer no alternatives, so re-cladding is recommended for any plaster-clad house with even a few minor issues.  We have seen dozens of instances where a full re-clad has only revealed a couple of small leaks.

The question of why the councils want you to re-clad is a little more complex but maybe even more insidious.  On the surface, the process of designing a re-clad, obtaining a building consent, having council inspections then having a new Certificate of Code Compliance makes total sense and ensures that the re-clad house has cavity construction, is weathertight and meets a reasonable durability standard.

Behind all of this though is Council’s knowledge of the potential liability for issuing consents and CCCs in the first place for buildings that are likely to leak and rot prematurely.  Now, when they process consents for re-clads, they ensure as far as they possibly can that all of the defective work that they approved 20 or more years ago is now gone.  That is one reason why re-clads are so expensive – you are paying to fix all of those bad design, construction and material decisions that the council should never have passed in the first place.

However, the opportunities now of holding the council to account are slim, so how do homeowners keep their houses safe while avoiding the re-clad?

Re-Cladding Doesn’t Fix The Biggest Problem

Whilst the popular perception is that monolithic plaster cladding were the main cause of leaky buildings, this is not correct.  The problems arose as a combination of the factors listed above; undertreated timber, no cavities, and designs that didn’t keep the moisture out of the framing.

The re-cladding process has evolved considerably since the early 2000’s.  Many early re-clads failed again because important defects were not removed. We are now up to about Re-Clad Version 10 as Councils and re-cladders find more and more things that need to be removed, replaced or altered to get the re-clad through the ten year warranty period.  No doubt in another ten years, re-clads will be even more complex and expensive, as lessons learned from the failures of todays re-clads are put into place.

However, the biggest underlying defect, not fixed by re-cladding, is the defective undertreated or untreated timber used for the framing.  During the re-clad, any decayed or discoloured timber is replaced and any ‘good’ remaining timber is treated with a brush on boron treatment, which experiments have shown is not effective at controlling decay if there is another leak.

That’s right, you may spend hundreds of thousands of dollars on a re-clad, but much of the structure of the house is still defective and vulnerable to decay.

The  Mature Approach To Maintaining Plaster-Clad Houses

But what if all of the leaks in the house could be located and the damage to the timber is only minor?

And what if the leaks could be stopped and any decay killed off?

And what if the timber could be treated so that it won’t rot in the future?

And what if there was a monitoring system in the house that gave an early warning if any new leaks started?

Would you really want to spend money on a re-clad, when for a tiny fraction of the cost you could still have a safe, dry house?

What if there was proof for potential buyers that the house doesn’t leak, isn’t rotting and can be maintained indefinitely.

If all of these “ifs” were true, should there still be a ‘stigma’ attached to the house when it comes time to sell?

Wouldn’t this be a more mature way of approaching the issue rather than automatically assuming the house needs a re-clad?

Now we are not saying that you never need to re-clad because for some houses there just is no alternative, however this should be a last resort rather than the default approach.

Most home owners can’t afford a re-clad but want to live in a safe, dry house and keep it that way.

Targeted Repairs And Treatment Vs Re-Cladding 

In 2005, the Moisture Detection Company patented the Mdu Moisture Detection Probes which have been installed discretely through the skirting boards in thousands of NZ homes.  This is the most sophisticated, accurate, moisture monitoring system available, and like the best products, it is simple and cost effective.

Once the probes are in all locations where there may be a weathertightness risk, you have detailed information on any wet framing, any decay and what, if any timber treatment was used.

From that position of knowledge, you can make an informed decision about what to do next; do nothing, do targeted repairs and treatment, or go on for the full re-clad.

Targeted repairs and treatment have these goals:

  • Stop the leaks and modify defective details to manage or stop future leaks.
  • Ensure that timber that may be affected by current or future leaks is protected by adequate treatment.  If the timber is untreated then post-treat with RotStop.
  • Remove and replace decayed timber if it is affecting the structural integrity of the house – or just treat it and leave it.

In this way buildings can be saved, remain healthy and liveable and for a lot less anxiety and costs. The Building Act does not mandate that no decay is allowed in a building. It does not even mandate no leaks. What it does mandates is that leaks are not to progress to cause structural problems, which is limited to load bearing, bracing and maintaining secure claddings and linings. External walls are often over engineered, with safety margins of 50% or more.  Leaving minor decay that has been treated in some walls has no effect on the structure and remains in full compliance with the Building Act.

Compare this to a re-clad where any timber within one metre of visibly stained wood is marked for replacement. This can mean expensive replacement even if the staining is due to the framing getting wet during construction and is still good, sound timber.

Moisture Probe System Schematic

Moisture Detection Company Philosophy

  • Gather evidence with Mdu Moisture Probes before making any big decisions or spending big money.
  • Locate and repair the leaks using the evidence from the probes
  • Identify vulnerable timber, and treat it in-place with RotStop to kill decay and protect against future leaks.
  • Replace timber only when decay is serious or affecting structural strength.
  • Monitor for new leaks, and build a history of dryness by reading the Moisture Probes regularly.

Homeowners who adopt this process can maintain a typical plaster clad house and have a comprehensive package of documentation to prove to buyers that their house does not leak, and is safe to buy.

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