For every $1 governments spend on increasing the resilience of existing buildings, $6 is saved in property losses, health costs and interruption to business, new US research has found.

The study, led by University of Colorado Boulder professor Keith Porter, also found that for every $1 spent exceeding building codes to make more hazard-resistant buildings, $4 is saved. In terms of health costs, improving both existing and new build resilience in the US would save 600 lives, and prevent one million injuries and 4000 cases of post-traumatic stress disorder.

Extreme weather conditions are increasing around the world, making improved building resilience critical. We know, for example, that many homes in Queensland aren’t built to withstand cyclones.

Last year UNSW climate scientist Andy Pittman told The Fifth Estate a cyclone hitting the Gold Coast would be “catastrophic” because of the area’s poor building standards.

In the US, the situation is dire, with 2017 seeing hurricanes Harvey, Irma and Maria, along with extensive Californian wildfires – likely representing the highest collective losses from natural disasters in the history of the nation.

Professor Porter said natural hazard losses in the States had exceeded US$300 billion (AU$383b) in 2017, meaning mitigation was critical. It’s also a win-win strategy.

“This study shows it pays to build new buildings better and to fix existing ones, and everybody wins when we do so,” he said.

In terms of improved building codes, the study said all stakeholders considered were provided benefits that outweighed costs, including developers, title holders, lenders, tenants and the broader community.

“When one subtracts the costs each group bears from the benefits it enjoys, the difference … is positive in each category.”

Professor Porter said there was nothing wrong with building codes in terms of their primary purpose of protecting human life, however they fell short in terms of preventing buildings from becoming unusable.

For example, his research showed that a 7.0 magnitude earthquake in metropolitan California would render 25 per cent of code-compliant buildings collapsed, unsafe or uninhabitable.

“We wanted to find out what would happen if the goal of codes were to protect human life and to have the most resilient building stock possible that still makes economic sense.”

The question asked by the research was: “What would the cost-benefit ratio be if, for one year, all new private sector buildings in high-risk areas were constructed to exceed existing codes?”

The study found that if private builders invested an additional $3.6 billion over a year to exceed current code requirements, the benefit to society would be $15.5 billion – a benefit-cost ratio (BCR) of 4.3, with some areas showing bigger BCRs.

“There are counties in California where it makes economic sense to make buildings three times as strong and stiff as code requires and the benefit cost ratio could reach 8 to 1,” Professor Porter said.

The study looked at potential damage caused by earthquakes, hurricane winds, river flooding, wildland-urban interface fires and hurricane storm surge, and the protection afforded by government funding of mitigation measures, and improved building codes.

“This past year was the costliest ever in the United States in terms of recorded disaster losses,”  CU Boulder’s Natural Hazards Research Center director Lori Peek said.

“This report charts a clear path forward, illustrating that investments that we make before disaster strikes can help reduce the harm and suffering caused by these events.”