Bushfire and flood overlays: what they mean for your shed

Bushfire-prone areas

The NCC's bushfire provisions, clause H7D4 in Volume Two, say that in a designated bushfire-prone area a Class 1 building, or a Class 10a building or deck associated with a Class 1 building, meets the performance requirement if it is built to AS 3959 or to the NASH Standard for steel-framed construction in bushfire areas. A detached shed out in a paddock is not associated with a house in the same way as a garage beside it.

The Queensland Government's guidance on building in bushfire-prone areas says the residential bushfire standard applies to new homes or outbuildings, rebuilding, repairs to garages and sheds, and additions to homes and outbuildings within six metres of a dwelling. Queensland also has a variation: the requirements do not apply where the classified vegetation is Group F rainforest (excluding wet sclerophyll), mangroves, or grasslands under 300 mm high.

Council planning schemes can add their own requirements in a bushfire overlay. Toowoomba Regional Council, for example, notes that a bushfire overlay may require a bushfire management plan and on-site water storage.

Flood hazard areas

Queensland's building code for floods, QDC MP 3.5, only applies where the local council has designated a flood hazard area and declared a defined flood level. Its purpose is to make specified buildings resist flotation, collapse or significant permanent movement. The buildings it lists are houses, some other classes and utilities for commercial buildings; Class 10 is not listed, and the state's guideline notes its utilities standards apply to all buildings except sheds and garages.

That does not mean flood areas are unrestricted for sheds. Council planning schemes control development in flood overlays and overland flow paths. Sunshine Coast Council, for instance, says domestic outbuildings on rural and rural-residential land must not interfere with overland flow paths or flood hazard areas, and Logan City Council's standard conditions include flood-level conditions for domestic outbuildings. Beyond the rules, storing machinery or a caravan in a shed that floods is its own reason to choose the site carefully.

Choosing where the shed goes

Overlays often decide the best position before anything else does. On bushland acreage, keeping a new shed well away from the house can simplify the bushfire requirements, while a garage joined to or close to the house is treated as part of it. On flood-affected land, the highest practical ground, clear of overland flow paths and drainage lines, protects both the approval and whatever you store inside. On rural blocks the 200 m building exemption for farm sheds may also pull the shed into the paddock. Weigh these against access, power and how often you will use the shed.

How to check your property

• Look up your lot in your council's planning scheme mapping for bushfire, flood, overland flow and landslide overlays.
• Use council flood tools where they exist: Toowoomba Regional Council has a flood risk portal, Ipswich maps flood risk in its City Plan overlay, and the City of Gold Coast publishes flood depth mapping.
• Note any mapped bushfire hazard and the vegetation around the proposed shed.
• Measure the distance from the proposed shed to your house; six metres is a key figure for bushfire guidance.
• Tell your shed supplier and certifier what you find, early. An overlay found after the design is finished usually means redrawing it.
• Keep a copy of the overlay maps with your approval documents; the certifier and council will refer to the same maps.

What BWG Sheds checks

Before we finalise a design we look at the overlays that apply to your lot, discuss the shed's position and its distance from the house, and allow for any construction requirement in the specification and approval documentation. Where an overlay needs council assessment, we coordinate it with the certifier and council.

Requirements depend on your property, proposed structure and local planning/building controls.