Monolithic Claddings Popular But Defect Prone

December 16, 2013

By Philip O’Sullivan
Registered Engineer, BRANZ Accredited Adviser, Registered Building Surveyor, Fungal Research, Moisture control, Civil Engineering and Building Pathology.
Trained as both an engineer and building surveyor, Philip has more than 20 years experience in all facets of building design and construction. Philip is responsible for bringng a range of pressing issues to the attention of the New Zealand construction industry. For example, Philip has identified the presence and cause of dry rot – not thought to be a significant problem in this country – in near new dwellings. He writes a monthly column for the Progressive Building magazine under the pen name, Dr Rot. Philip is the Prendos representative and current Chairman of the Cladding Institute, Prendos is a corporate member of that Institute.

The Building Industry Authority-Funded UNITEC Cladding Defects Survey arose from concerns in the building industry over the poor weathertightness performance of some house claddings, particularly in houses built since the Building Act came into force in 1992. The Building Industry Authority (BIA) commissioned UNITEC to carry out the study as a first step towards establishing the extent of any problems and to indicate directions for further research in this area.

This ground breaking research was based upon 287 reports of prepurchase inspections carried out by Prendos Limited between 1996 and 1999. Prendos initiated the idea of this study through its involvement in organisations such as the Building Surveyor’s Institute and the Claddings Institute.

It was found that more than half of the houses in the sample had a defect that could let moisture in, either through the cladding, windows/doors, or through defects in decks or balconies.

About 60% of the houses with defects had more than one and some had up to five defects. Five percent of the houses were significantly defective. One house had 39 cladding defects. Around 30% each of the stucco and textured fibre cement defect cases were recorded as having mosture present. This compares to 17% for brick veneer and 14% each for timber and polystyrene based cladding systems.

For houses built before 1990, the number of defects per house was fairly constant – an average of about one defect per house. However, in the 1990/2000 period, the average number of defects per house almost doubled.

The value of the UNITEC survey was that it challenged some of the preconceptions about the relative significance of cladding type and junctions. Further research is needed to answer some of the questions raised by this survey.

Results also confirmed a changing pattern in cladding materials, particularly over the last ten years. The use of monolithic claddings has arisen to 38% of claddings compared to 9% in the 1980’s.

Prendos is currently undertaking further research in this area and will release its findings next year.

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