Can Timber Frames Meet BAL 40? Bushfire Compliance Explained
Transcript
(Attendee): Yes, I should say we are in a very high bushfire alert level, probably a BAL 40.
Charles Christodoulou: Yeah. Then we have to work all that out – a BAL rating of 40.
Charles Christodoulou: And if it gets really expensive if you’re FZ.
(Attendee): Yeah. I don’t expect we are, but…
Charles Christodoulou: In FZ you require steel shutters to the windows and they’re about $5,000 per window. It’s a nightmare.
(Attendee): But going to a BAL 40, it can still be timber framed at BAL 40, can it?
Charles Christodoulou: Yeah, I think so. Yes.
(Attendee): I thought they might have tipped over the scale and said it’s got to be…
Charles Christodoulou: No, no. Because the external part of the house – we need to protect the eave lining, the subfloor has to be covered properly, and your cladding has to meet BAL 40 requirements. So it’s very hard for embers to get into the timber frame internally or under the house, because that has to be enclosed within regulations.
Yes. A timber frame can meet BAL 40 when the external components are detailed to the relevant bushfire standards.
What BAL 40 means for timber frames
Compliance at BAL 40 focuses on protecting the external envelope so embers and heat don’t penetrate to the frame. In practice, the outside of the home must be specified and built to the required protections, while the structural frame may remain timber.
Key elements that must be protected
- Cladding: Use wall claddings that meet BAL 40 requirements so the exterior resists ember attack.
- Eaves/soffits: Protect and line eaves appropriately to prevent ember entry.
- Subfloor: Enclose the subfloor to the required standard so embers cannot access underfloor areas.
BAL 40 vs BAL FZ
BAL FZ (Flame Zone) is significantly more demanding. As an example, steel shutters to windows were cited at about $5,000 per window under FZ requirements. BAL 40 is below FZ and can be achieved with a timber frame when the exterior is detailed correctly.