How bushfires ignite buildings

Have you ever wondered just how flammable your home really is? What exactly is it that burns when a bushfire passes through and what is most likely to catch fire first?

That’s a powerful question — and a really important one if you live in a bushfire-prone area.

When a bushfire passes through, your house doesn’t usually “burst into flames” all at once. It typically ignites because of a few specific weak points. Let’s break down what actually burns — and what usually catches first.

What Actually Burns in a Bushfire?

A bushfire affects homes in three main ways:

1. Ember attack (the biggest cause of house loss)

Burning embers (firebrands) can travel kilometres ahead of the main fire front. These land on or around your house and start small spot fires.

They ignite:

• Dry leaves in gutters

• Mulch or garden beds

• Timber decking

• Door mats and outdoor furniture

• Gaps in roof spaces

• Underfloor areas

• Fences attached to the house

Most homes are lost from embers — not from direct flames.

2. Radiant heat

Even if flames never touch your home, intense radiant heat can:

• Crack or shatter windows

• Melt window seals

• Ignite curtains inside

• Warp vinyl window frames

• Cause timber cladding to pyrolyse (chemically break down and ignite)

If a window fails, embers and flames enter the house — and internal contents burn rapidly.

3. Direct flame contact

This happens when vegetation, fences, or nearby structures burn right up against the house.

Flames can ignite:

• Timber weatherboards

• Eaves and roof cavities

• Decking

• Attached pergolas

• Gas bottles

• Carports

So what usually catches fire first?

In most bushfire house losses, ignition starts with:

Gutters cleared of dried leaves are a thing of beauty!

• Gutters full of dry leaves

Embers land → leaves ignite → flames reach roof edge → roof cavity ignites.

• Timber decking

Especially if there’s leaf litter between boards or underneath.

• Mulch against walls

Fine fuels like bark mulch ignite easily from embers.

• Fences attached to the house

A burning timber fence can act like a fuse line straight to your wall.

• Broken windows

Radiant heat cracks glass → curtains ignite → internal flashover.

What inside the house burns?

Once fire enters:

• Curtains and blinds

• Upholstered furniture

• Bedding

• Carpets

• Paper, books

• Plastic appliances

• Kitchen cabinetry

Modern synthetic furnishings burn much faster and hotter than older natural materials.

Why houses burn so easily

Your home contains:

• Dry timber framing

• Plastics (vinyl, foam insulation, wiring)

• Fabrics

• Paints and sealants

• Stored fuels (cleaning products, aerosols)

Even brick houses can burn because:

• The frame is usually timber.

• The roof structure is combustible.

• The contents are highly flammable.

The counter-intuitive truth

The surrounding bush is not always the main problem.

Often the smallest fuels closest to your house are the most dangerous.

A house surrounded by managed vegetation can survive even extreme fires.

A house with leaf litter, gaps, and combustible attachments may not.

How we can assist

Morrahan Services offer home safety consultations and reports that will assess your property, dwelling/s, vegetation and aspects of greatest risk and offer advice to homeowners regarding measures that may be implemented to enhance the dwellings resistance to bushfire exposure.