Reducing flood damage to NZ homes

February 2016

A small scale flooded test house - part of the BRANZ research project Flood It. Photo: Branz.

The Canterbury Earthquakes aside, the highest number of insurance claims for New Zealand homes is because of water and flood damage. With recent extreme weather patterns, such as those causing flooding in Christchurch's Flockton basin, many communities want to know how to repair their homes and whether the use of different materials would have had a better outcome.

As part of their research project, Flood It, BRANZ have set up a number of small scale test houses – and flooded them. The research aims to study the effect of floods on building materials so designers and homeowners can make choices that reduce flood-water damage, support faster recovery, and minimise insurance costs.

During the tests, the houses were flooded to half a metre above the internal floor level so researchers could examine the behaviour of building materials, such as insulation behind plasterboard, following a flood. Sensors monitored the temperature, humidity and moisture in the wall cavities.

A 30,000 litre rainwater tank was used for each test, so no pressure was put on town supplies while running the experiments. The small houses were soaked in the flood-water for 24 hours before it was pumped away. The interior wall cavities were tested and conditions monitored for the next six weeks before the walls were opened up to assess their internal condition. This approach provided the researchers with the chance to test the effectiveness of some typical approaches to drying out a house after a flood.

The ongoing research is examining the effects of repeated flooding, methods of drying (such as heating, dehumidifying and ventilating), and house-level protective measures such as door barriers. It will also examine the effectiveness of small changes to existing building practice, such as painting all sides of skirting boards rather than just the exposed faces, to see if they offer any benefits.

Building Research Levy Investment 2015/16

The BRANZ Research Levy Investment booklet Levy in Action for 2015/16 is now available.  The booklet describes the wide range of research and knowledge dissemination activities funded by the Building Research Levy. Of interest to researchers, industry practitioners and government, it provides snapshots of current research being carried out by both BRANZ and external providers. Copies are available from the BRANZ website.