How does a factory-built home handle bushfire and flood risk?

Most Australian sites carry a hazard rating of some kind. In New South Wales that usually means a bushfire attack level, a flood planning level, or both.

Neither is a reason a site cannot be built on. Both change what gets built.

Bushfire starts with the assessment

A site is assessed for bushfire attack level based on the vegetation around it, the slope, and the distance between the two.

That rating sets the construction requirements, and they escalate sharply across the range. A dwelling at a low rating and one at a high rating are genuinely different buildings.

The assessment happens before design, not after, because it decides the glazing, the external materials, the subfloor treatment, the roof and the screening.

Embers do the damage, not the front

The common picture of a bushfire is a wall of flame reaching a house. In practice most homes are lost to embers arriving ahead of the fire and finding a way in.

Which means the whole argument is about gaps.

Gaps around windows and doors. Unscreened vents. Openings in the subfloor. Roof penetrations. Junctions between materials where a small opening was never closed.

Every one of those is a detail, and details are where site construction is least consistent, because they get executed at the end, at height, in awkward positions, by different trades.

In a controlled environment the sealing is done at a fixed station, to the same documentation, and inspected before anything covers it. That is the same argument as [factory quality control](/blog/factory-quality-control-and-tolerances) and it applies with more force here, because the consequence of one missed gap is total.

What changes in the build

**Glazing.** Higher ratings require toughened glass and screening, with the frames rated as well. Glass is frequently the first failure point.

**External materials.** Non-combustible or rated cladding, and the detailing behind it.

**Screening.** Every vent, every opening, at the required aperture.

**The subfloor.** An enclosed or protected underside rather than an open one.

**Decks and attachments.** These are often the item that ignites and then delivers fire to the building.

Flood is a levels problem

Where a flood planning level applies, the habitable floor has to sit above it.

On a site with a significant level, that either means fill, or it means elevating the structure. Both are ordinary engineering decisions and both interact with the access requirements, because a raised floor still has to be reached by a compliant path.

Below the flood level, the requirements change: flood-compatible materials, services located above where practical, and a structure designed for the forces water applies.

Where the two collide

Plenty of sites carry both. A raised floor for flood and ember-proof detailing for fire are not in conflict, and they do have to be resolved together rather than sequentially.

Getting that resolved during the [design stages](/blog/the-eight-design-stages-explained) is what keeps it from becoming a variation once fabrication has started.

The honest position

We do not publish ratings a dwelling meets as a general claim, because the answer is per site and per design.

What is true generally is that hazard compliance is executed through detailing, and a build carried out in controlled conditions and inspected before enclosure executes detailing more reliably than one that does not.

Send us the site and its hazard rating and we will work through it.

MADEmodular / MADEbetter.