When looking to build or extend your home in Moreton Bay, if you are in the flood overlay you may be required to construct the building out of water resilient materials. In that instance you may find yourself asking – what exactly is a water resilient material?
What is a water resilient material?
A water resilient or water resistant material is a building material that has a higher water resistance rating. Effectively it doesn’t dissolve or perish easily once water is introduced. These may include using fibre cement sheeting, brick or block work, ceramic wall tiles, solid wood and fully sealed durable timbers including hardwood, galvanised steel sheet or glass and glass blocks, instead of your typical building materials. A full explanation of building materials that are resistant to water, as required by the Flood overlay code is included in the fact sheet found here:
Why would you use water resilient materials instead of just building above the flood level?
While it may be possible to build your habitable rooms above the defined flood level, plus the required freeboard, it may not be practical, or cost effective to build non-habitable rooms at this level.
A quick recap on the terminology we’re using here – a habitable floor level is defined by the Moreton Bay Planning Scheme as the finished floor level of a room:
“which is designed or used on a regular basis for a residential accommodation activity.
Examples include: bedrooms, living rooms, rumpus rooms, hobby rooms, kitchens, toilets, ensuites, laundries and home offices.
Exclusions: spaces that are permanently open to the elements on one or more sides; rooms with an earth floor; spaces designed or used solely for car or other vehicle accommodation”.
A non-habitable space is typically a space used for a garage, laundry, bathroom, lobby, clothes drying room, and other spaces of a specialised nature that are not occupied frequently or for extended periods.
Building above the defined flood level may be expensive, or in some circumstances cost prohibitive for the works you are wanting to carry out. Therefore, the opportunity for alternate materials to be used exists. However, if your site is subject to significant flood depth, or high water flow (velocity) you may need to talk to a hydraulic engineer first as the requirements for your structure will change to ensure it can withstand the water flow.
The requirement to use water resilient materials is to ensure the residents do not incur significant expense each time a flood event occurs. It allows for those areas that are not used often to be below a flood level, provided they meet the requirements.
These provisions regarding design and materials relate specifically to properties in the Moreton Bay Regional Council area and governed by their planning scheme. Each local government treats flooding and the regulation of building work on flood prone land differently.
If you are looking to purchase or develop land that is subject to flooding, you should always talk to a town planner to gain a better understanding of your options. In some cases you may also need to talk to a hydraulic engineer to gain a better understanding of how the flooding affects your site.