From today, floors in houses to be built in low-lying areas of Dunedin could be up to 1m off the ground following the introduction of new "interim" minimum floor levels.
The Dunedin City Council has made the changes in response to concerns following the floods in June 2015.
DCC building solutions principal adviser Neil McLeod said staff had been analysing flood data and other information as it became available, and found it was now necessary to implement new minimum floor levels for residential accommodation in areas such as South Dunedin, the Taieri Plain, Brighton, Tomahawk and parts of Kaikorai Valley.
"The new levels will provide a greater level of protection for new residential buildings in heavy rainfall events.
"The changes are a practical, interim solution for these types of buildings to deal with flooding associated with one-in-50-year rainfall events," he said.
The council already had minimum floor levels in some areas of the city, such as low-lying coastal areas, and these levels would continue to be applied.
For areas flooded in 2015, the new minimum floor levels will be set at the height of the floodwaters, plus another 400mm.
In other flood-prone areas which were not affected by the floods, the new levels will be ground level plus an additional 500mm.
In most other places around the city, floor levels would remain at 150mm above the crown of the road, as per the New Zealand Building Code.
Mr McLeod said the effect of these levels on individual properties would be very "site-specific" and depended on where the property was and what information was known about it.
As a result, the floors of some houses could sit up to 1m above ground.
The new floor levels apply to buildings in the categories of housing (a house, flat, multi-unit apartment or marae), communal residential (a rest-home, hospital or holiday camp) and communal non-residential (church, kindergarten, school, cinema, hall or clubrooms).
They do not apply to commercial premises such as factories or warehouses.
Mr McLeod said there were four building consent applications in the system where the new levels would apply, and the DCC was working with individual applicants.
He believed the new levels would affect only about a dozen building consent applications each year.
Staff would be talking to industry groups and other stakeholders about the changes and what they mean.
The DCC hoped to provide detailed maps in coming months that would show what levels applied to individual properties.
"We are still working with other agencies to gather and present that data, but we do have sufficient information now to be able to broadly apply the new levels."
Mr McLeod said the new levels were "interim" because the council and other organisations were continuing to gather information about climate change and other challenges, which may have a flow-on effect for minimum floor levels.
"We need to be able to respond as new information comes through."
The changes meant it may cost more to build the types of properties outlined above, or extensions to them.
People could still propose an "alternative solution" to the new minimum floor levels if they believed they could provide a design that would reduce the flooding risk to the property in other ways, and which complied with the building code, he said.
Property Council New Zealand Otago Chapter president Geoff Thomas said the new floor level recommendations were "sensible".
But he was concerned about how it would affect the state of housing in places such as South Dunedin, when combined with the second generation Dunedin city district plan (2GP) which proposed making all residential properties in the area movable.
The proposal aims to allow home owners to move their homes to higher ground in the event of future sea level rises.
Mr Thomas was worried South Dunedin would look like a sea of "prefabricated houses on stilts".
Foundation plan
• Floor levels in areas which flooded in 2015 will be set at the height of the floodwaters, plus another 400mm.
• Other areas identified as flood prone will be ground level plus an additional 500mm.
• In most other places around the city, minimum floor levels will remain at 150mm above the crown of the road.
