As a newcomer to the role of building surveyor with Prendos, I arrived with the broad experience of a builder and the narrower mindset of a quantity surveyor. I had the idea that if a building had a problem, you located it and fixed it as economically as possible.
I now know that this approach holds true only in certain situations and that it is likely to be the wrong approach with regard to weathertightness issues.
The ‘locate and fix’ approach is a targeted repair. The alternative is a total repair, which includes recladding.
To a minimalist like myself the shift in thinking from one to the other is radical but more experienced members of the Prendos team have proven this approach right and sensible.
Property owners, however, have an understandable difficulty accepting this. The total repair of what they perceive as a singular problem seems unwarranted. But what at first glance seems an expensive form of overkill makes sense when looked at more closely.
Firstly, to the untrained eye a weathertightness problem may appear to affect only one or two isolated areas of the building. But most buildings are of a given construction type, and if the underlying fault lies with the design details and building systems that make up that construction type, the problem area is potentially much greater.
Targeted repairs are also less likely to make use of recently revised building methods because they do not readily fit in with what is already there. Under these circumstances, repairs can easily become a bandaid, leaving fundamental problems unchanged or unwittingly compounded.
Secondly, areas that do not give any indication of suffering a similar problem at the time of an initial investigation can, if left undisturbed, develop problems later. The speed at which decay symptoms develop may vary from weeks to years, but when dealing with decay fungi and untreated framing there’s no way that targeted repairs carried out at the owner’s insistence can guarantee a clean bill of health. The risk is that latent decay not detected during targeted repairs, will suddenly flourish under suitable conditions.
In short, targeted repair risks not only leave an owner with a situation more likely to fail, it constitutes false economy when followed by total repair.
The overseas experience also holds true. Targeted repairs carried out on many of the affected buildings in Vancouver, Canada, have since required total repair. Prendos has evidence of this also happening here.
The change in thinking at Prendos from one method to the other was at first gradual, and then it gathered pace. While carrying out repairs to leaky buildings in Auckland in the 1990s, Prendos directors Greg and Philip O’Sullivan became aware of the extent of damage and the potential for catastrophic damage caused by various types of timber decay, particularly with modern types of construction.
Greg first considered using a cavity system back in 1996 but thought no one would wear the idea. In 1997-98 Prendos installed a cavity cladding system on a boron-treated frame which had the rot removed but was still very wet. The cavity was intended to allow the wet framing to dry out; it worked and the cladding still looks good today.
In 1998 and 1999 Greg and Philip wrote articles and gave presentations to legislators, regulators and industry bodies, voicing their concerns regarding the consequences of using untreated framing and the high level of failure of modern monolithic cladding systems. By the time of the May 2000 CINZ Weathertightness Forum, the nature of the problem was clear but there was still no certainty within the industry on how best to deal with it.
Up until then, Prendos carried out predominantly targeted repairs. The Prendos database reveals a definite change in method from 2000, when jobs listed as ‘Reclad on Cavity’ begin to appear. Five years later, recladding on a cavity is the predominant solution and in many cases, the only sensible option.
In isolated cases Prendos still recommends targeted repairs but only after careful consideration of the risk factors and on behalf of clients who are prepared to monitor the repairs for any sign of future failure.
by Simon Cotter
Simon Cotter is a qualified builder, quantity surveyor and communicator with twenty five years’ experience in the building industry. In addition to his time as a front-line builder he has worked as a journalist, tertiary tutor and editor of industry trade journals, including the well-known construction industry magazine, Progressive Building.