15 Oct 2015

Houses flooded in the name of science

6:48 pm on 15 October 2015

A small wooden house sits in a 30,000 litre pond, water lapping half a metre above its floors.

But this is no act of Mother Nature; a large green hose trails over the side of the pond.

It's the third such building to be flooded by building research company BRANZ as part of 'Flood It!': a three-year, $300,000 project to help designers and homeowners choose flood-resilient building materials.

The building flooded today will remain underwater for 24 hours before water is pumped away and approaches to drying the walls are tested.

Research team leader Dr Patricia Shaw said the aim of the research was to get residents back into their homes faster and reduce flooding's financial impact.

"Flood damage has never been tested in a systematic, rigorous, quantifiable way. This project gives us the opportunity to test how effective we can be in reducing significant water damage."

Researchers flooding a house to gain vital insight for builders.

Today's test subject is the third of four small houses to be built and flooded by BRANZ in Wellington. Photo: RNZ / Alexander Robertson

Four small-scale houses have been built at the BRANZ headquarters and the first, flooded in February, is already yielding results.

"Where ventilation holes were cut into the wall, the insulation and framing was visibly drier than where the lining was left intact. Where there was no ventilation, mould developed behind the skirting boards," Dr Shaw said.

"One surprising observation was that, after six weeks, insulation still held water in the lower part of the wall, more so when there was no ventilation. In the closed walls, the framing was still visibly wet."

The damage resembles what many New Zealanders may already have experienced.

According to BRANZ, data from the Ministry of Civil Defence has shown flooding causes $125 million worth of damage a year - with about 1086 houses affected.

BRANZ materials team leader Nick Marston said he hoped the company's project would deliver useful information for home owners.

"Really what we're hoping to get out of this is some good information that we can share with home owners, with the industry, around making smart decisions around specifying more floodwater-resistant materials.

"And also, if you are unfortunate enough to get flooded, to give you some good quality information about what the best thing is to do to dry your house out and get your house rehabitable as quickly as possible."

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Flooding has been estimated to cause $125 million worth of damage a year in New Zealand. Photo: RNZ / Alexander Robertson

Wellington Region Emergency Management Office spokesperson Bruce Pepperell said flooding was a large risk, with two significant floods in the region in the last three months.

"We sometimes think of the infrastructure but it's the impact on people which is important. Anything like this is going to give people a little bit more surety their loss is going to be lowered or perhaps eliminated."

He said, if it could help people move on and recover faster, it would be a great result for communities and insurers.

With a fourth house due to be flooded next year, Mr Marston said future tests would see these buildings flooded again as researchers explore different drying methods and materials.

"They're all destined for a hard life."

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