A guide from City Surveyors Newcastle: from the flood map to your floor level.
On flood prone land in Newcastle, the floors of occupiable rooms need to sit at or above the flood planning
level: the flood level plus a safety margin called freeboard.
The flood map and council's Flood Information Certificate give you the flood level.
They do not tell you where your floor or your ground sits.
That takes a survey on the same height datum council uses, the Australian Height Datum, or AHD.
Start with council's flood information viewer.
Council says flooding affects up to one third of all properties in Newcastle.
Land within the probable maximum flood is treated as flood prone land.
On the map and the certificate you will see the 1% AEP flood, a flood with a 1% chance of happening in any year,
and in newer studies the 1% AEP in 2050, which allows for climate change.
Which rules apply depends on your area's flood study, so always use the levels on your own certificate.
Council issues three kinds of Flood Information Certificate.
A general certificate is for a development application or general use.
A complying development criteria certificate is for a complying development application.
And an additional assessment is only needed if council asks for it.
A general certificate typically takes 10 to 14 business days, and for a development application it must be no more than 12 months old when you lodge.
The floor rule is built around the flood planning level: the planning flood plus a freeboard that is generally 500 millimetres.
Floors of occupiable rooms must not be lower than it.
Small additions to an existing building can fall outside the flood section under a minor additions exception.
For example, if the existing building is under 250 square metres, the limit is 50 square metres.
Council decides each application.
Here is the step the map cannot do.
Council's levels are on AHD, and its certificate notes say they can be compared with ground levels a surveyor measures on the same datum.
A survey of the site's levels, existing floors and features, all to AHD, lets your designer show exactly where the new floor sits.
In Lake Macquarie, a different council applies, with its own flood tool and certificate.
Our guide for a survey of a site's levels and features is 1,200 to 3,500 dollars or more,
and most are completed within 5 to 7 business days from booking.
Building or extending on flood-affected land?
Send us the address and a short note about your plans, and we will quote it for free.
Or call (02) 4003 6416.
This is general information, not planning advice.