High Hopes – Building inspection technique delivers the goods
This appeared in the ‘Straight Up’ magazine from BOINZ, September 2008.
Due to the hidden nature of buildings, we all place huge reliance on building diagnostics techniques to understand building weathertightness performance. These techniques are designed to inform and therefore improve decision making throughout a building’s life. The results of a recent study shows that a new inspection tool has taken a serious step forwards.
This study was conducted by Project M, a cross-disciplinary research initiative led by Ian Holyoake from Moisture Detection Ltd, on over 700 homes in New Zealand. Its aim is to analyse 1000 homes to better understand how to measure building performance accurately over time. The analysis tool being used is the patented Mdu Probe System – taking timber strength readings, timber samples, and regular moisture contents using the Mdu Probe at approximately 70 locations per house. The Mdu Probe System results have now been compared to other investigation processes from the same buildings. It was found that the Mdu probe (in comparison with other non-destructive systems) identified more accurately in every case areas of timber damage and moisture ingress. By contrast many of the areas other tools claimed were defective and been condemned were found to have good performance by using the Mdu probe system. Incorrectly analysing performance often paints a bleak picture and this can lead to inaccurate or incomplete conclusions and a failure to adequately locate and isolate what the real problems are.
Themo-imaging camera inspections were carried out on a number of homes both before and after the Mdu Probe System assessment took place. Cameras failed to pick up problems, or show good performance reliably. In house 710 with the thermo-imaging camera first, its analysts failed to identify over 10 locations of structural or moisture problems – giving the house an all-clear. In house 433 the thermo-imaging analyst was shown the 4 locations where moisture ingress and timber damage had been shown to be present, and they failed to pick up any positive discernable pattern in those areas. 3 areas were also falsely identified to have a problem when in fact there was not.
Gib Scanning was done at the same time and location as the Mdu Probe System information was collected to over 37,000 locations. The Scan results when analysed were no better than tossing a coin in problem identification. In locations where the scanner indicated an ‘acceptable’ range, approximately 50\% were found to have either higher moisture levels or timber damage was present. In contrast the locations where the scanner indicated an ‘unacceptable’ range, approximately 50\% had acceptable moisture levels. Both scanning and cameras should not be used as a ‘first step’ in investigations.
Point-in-time assessments either missed key issues as they are limited in nature, or exaggerated problems found. A DBH Determination point-in-time assessment of House 382 passed the house with flying colours and could not find a single issue. However 2 months afterwards, the Mdu Probe System identified 4 locations of total rot, and 14 locations of raised moisture levels. Similarly a WHRS point-in-time assessment of House 802 suggested approximately $15000 of repairs were needed on a building. However The Mdu Probe System later found much more damage, and would have prepared the owner to where the repair bill now rests. In contrast, a private point-in-time assessment of House 814 condemned the house recommending a reclad. The Mdu Probe System later found the house had treated timber, most areas were performing and only had isolated and minor issues. The house is now being gradually repaired and monitored at much less cost.
The Mdu probe has shown its credentials and is sure to become the preferred diagnostics tool. It provides an accurate and reliable picture of a buildings condition and ongoing performance.
The Mdu probe is being used for determination assessments, WSG inspections, CCC reasonable grounds evidence reports and as a QA program for reclads and repairs. For more information on the Mdu probe consult your NZIBS or BOINZ weathertightness member or visit www.moisturedetection.co.nz. Houses referred to above can be viewed on www.bnet.org.nz in secure mode.