25 May 2016

Share this story

There’s been a lot of talk about floor levels lately and a lot of confusion about the height your floor needs to be to protect your home from flooding. Here are some answers to questions we’ve been hearing.

Why does the Council set minimum floor levels?

The Council sets minimum floor levels (the height the floor of your building needs to be) to protect homes and buildings from the damage done by flooding, now and in the future.

If you are building a new home, rebuilding or extending, you’ll need to think about the height you build your floor to so that it’s protected from flooding due to extreme weather events.

How does the Council decide how high the floor needs to be?

The Council uses flood modelling information that tells it where water may reach in the event of a flood. The modelling includes a ‘freeboard’ which is an extra allowance to take into account things like modelling inaccuracies and natural environment factors such as the effects of waves and wind.

The freeboard the Christchurch City Council uses is 400mm.

How do I know how high my floor has to be?

If your property is in a Flood Management Area, defined in the Christchurch District Plan, and you are building, or adding to your building, you may be required to meet a minimum floor level to protect from a 1-in-200 year flood event.

Over 50,000 residential properties in Christchurch lie within these Flood Management Areas.

Find information about floor levels at your property.

If I’m rebuilding my home, are the rules different?

If you are rebuilding your home, you may be able to exercise Existing Use Rights (if you rebuild within 12 months, on the same footprint, and the same sized house) without having to comply with the updated floor level requirements under the Christchurch District Plan. You would still need to meet the requirements under the Building Act, to comply with the Building Code minimum floor levels, which provide protection from a 1/50 year flood.

While the Council can't legally require you to build at the 1/200 level in this situation, we strongly advise people to consider rebuilding at the higher floor levels to give you better protection from flooding.

I am having earthquake repairs done to my home, do I need to consider floor levels?

Minor repair work does not trigger a minimum floor level requirement. But if your repair work requires a building and/or resource consent, like a full replacement of the foundation, floor levels would come into consideration. The consent process would trigger a reassessment of whether the floor level was high enough to comply with minimum floor levels under the Building Code and/or the new requirements of the Christchurch District Plan.

What allowance does the Council make for sea level rise?

The Building Act requires the Council to look at least 50 years ahead and the Coastal Policy Statement, that guides district plan provisions, asks the Council to look out at least 100 years. The actual rate of sea level rise over the next 50 and 100 years is uncertain. However, taking into account national guidance and the most up-to-date science on sea level rise the Council considers it prudent to plan for 0.5 metre over the next 50 years and 1.0 metres over the next 100 years, so these levels are factored in when setting floor level heights.

What else is the Council doing to help protect homes from flooding?

Christchurch is a flat, low-lying city, so there have always been areas prone to flooding. The earthquakes have worsened flood risk in many areas, with land subsidence and damage to waterways, land and land drainage infrastructure. Stopbanks have been raised in the worst affected areas close to the rivers and subject to tidal flooding.

And the Council’s Land Drainage Recovery Programme is working to reduce flood risk throughout the city to pre-earthquake levels. The Land Drainage Recovery Team have a prioritised programme of flood remediation work for flood-prone areas across the city.

Get information on stormwater projects in your neighbourhood.

I’m building, and need advice on floor level requirements, where should I go for information?

Visit the Council website and if you still have questions about your build, contact the Council on 941-8999 and ask to talk to the Duty Planner.