Changes to minimum floor levels

Dunedin (Thursday, 11 May 2017) – Most new houses in low lying areas of Dunedin will be built higher off the ground than previously under changes now in effect.

The Dunedin City Council has responded to concerns following the June 2015 floods and is introducing new minimum floor levels for mainly residential buildings, including new homes, house extensions and resthomes, across low lying parts of the city. In most areas, these levels will be higher than the current specifications.

DCC Chief Executive Officer Sue Bidrose says, “The key issue is that we are taking practical but manageable steps to protect new homes in low lying areas. This is not about making development difficult, it’s about being responsible and responding to the concerns of our community.”

DCC Principal Advisor Building Solutions Neil McLeod says staff have been analysing data from the June 2015 floods and other information as it has become available, which has led to new minimum floor levels for residential accommodation in low lying 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.”

The DCC already has 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 which flooded in 2015, the new minimum floor levels will be set at the height of the floodwaters, plus another 400mm. In other areas identified as flood prone which were not affected by the floods, the new minimum floor levels will be ground level plus an additional 500mm.

In most other places around the city, the minimum floor levels will remain at 150mm above the crown of the road, which is the ‘acceptable solution’ contained in the New Zealand Building Code.

The effect of these levels on individual properties is very site specific and depends on where the property is and what information is known about it.

The new minimum floor levels apply to buildings in the categories of housing (e.g. a house, flat, multi-unit apartment or marae), communal residential (e.g. a resthome, hospital or holiday camp) and communal non-residential (e.g. a church, kindergarten, school, cinema, hall or clubrooms).

The changes are likely to affect small numbers of proposed buildings. At the moment there are four building consent applications in the system where the new levels apply, so at this stage the DCC is working with individual applicants. Staff will also be talking to industry groups and other stakeholders about the changes and what they mean.

The DCC hopes to be able to provide detailed maps over coming months that show what levels apply to individual properties.

Mr McLeod says, “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.”

The new levels are interim because the DCC and other organisations are continuing to gather information around 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 mean it may cost more to build the types of properties outlined above, or extensions to them. The extra costs could relate to more engineering design required and because material costs will increase as foundations have to be higher.

People can still propose an ‘alternative solution’ to the new minimum floor levels if they believe they can come up with a design that will reduce the flooding risk to the property in other ways and which complies with the Building Code.

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