Bushfire Roofing Systems Design Guide
Every new home built or renovated must undergo a BAL (Bushfire Attack Level) assessment as part of the application for a building permit.
The attached site BAL assessment brochure determines the construction methods that must be used to better protect properties from the threat of bushfires.
The BAL assessment takes into consideration a number of factors including the Fire Danger Index, the slope of the land, types of surrounding vegetation and its proximity to any building.
A building surveyor will use AS3959 to check compliance with the construction requirements of the standard.
The following BAL 12.5-40 construction system details have been developed by CSR Bradford based on our interpretation of AS3959. Full compliance with AS3959 is confirmed by the relevant Fire Authority (CFA, RFS etc) of the applicable local council.
For FZ tile roofs, details provided set out the construction requirements for tile roofs as tested by Exova Warrington Fire; Fire Testing Report RIR 23987-04.
For Metal roofs in BAL-FZ areas, there are 2 methods for Deemed-To-Satisfy compliance; AS 3959 Construction of buildings in bushfire – prone areas, and NASH Standard for Steel Framed Construction in Bushfire Areas.
Details provided in the BAL FZ Metal Roof section set out the construction requirements for metal roofs.
All drawings (within the brochure) are for illustration purposes only and is not intended to be an install guide. Not all components are fully drawn and/or labeled.
Download the Bradford Brochure - Click on the image below!
- Introduction
- What do these BAL zones mean?
- Roofing system requirements
- Roof system selector
- BAL – 12.5 – BAL – 40 Tiled Roof
- BAL – 12.5 – BAL – 40 Metal Roof
- BAL - FZ Tiled Roof
- BAL – FZ Metal Roof
- Products for bushfire roofing systems
- Maestro BAL power roof ventilator
- Health & Safety
- Product Warranty
- Download Bradord's Bushfire Roofing System Brochure
2.0 What do these BAL Zones Mean?
BUSHFIRE ATTACK LEVEL (BAL) | DESCRIPTION OF PREDICTED BUSHFIRE ATTACK AND LEVELS OF EXPOSURE |
|---|---|
BAL – Low | There is insufficient risk to warrant any specific construction requirements but there is still some risk. |
BAL – 12.5 | There is risk of ember attack. The construction elements are expected to be exposed to a heat flux not greater than 12.5kW/m2. |
BAL – 19 | There is risk of ember attack and burning debris ignited by wind borne embers and a likelihood of exposure to radiant heat. The construction elements are expected to be exposed to a heat flux not greater than 19kW/m2. |
BAL – 29 | There is an increased risk of ember attack and burning debris ignited by wind borne embers and a likelihood of exposure to an increased level of radiant heat. The construction elements are expected to be exposed to a heat flux not greater than 29kW/m2. |
There is a much increased risk of ember attack and burning debris ignited by wind borne embers, a likelihood of exposure to a high level of radiant heat and some likelihood of direct exposure to flames from the fire front. The construction elements are expected to be exposed to a heat flux not greater than 40kW/m2. | |
There is an extremely high risk of ember attack and burning debris ignited by wind borne embers, and a likelihood of exposure to an extreme level of radiant heat and direct exposure to flames from the fire front. The construction elements are expected to be exposed to a heat flux not greater than 40kW/m2. |
3.0 Roofing systems requirements
A rigorous process of independent research and testing has resulted in a range of compliant roofing systems designed to withstand the threats in each BAL.
The following table outlines roofing requirements incorporated into the standard for each BAL zone.
4.0 Roof system selection
To select the compliant roofing system for your project you need to first identify the BAL classification for your site and determine whether your roof will be tiled or metal clad.
Please note that the following is a guide and CSR Bradford recommends that you work closely with your building surveyor/private certifier, fire engineering consultant and insurance provider early in the design phase of your building to ensure compliance where appropriate to your specific building type and project requirements.
The system drawings provided are not drawn to scale and are not intended to be an installation guide, for further fixing details contact CSR technical support.
4.1 BAL-12.5 – BAL-40 Tiled Roof
For compliance in BAL-12.5 to BAL-40 areas, tiled roofs shall be fully sarked. The sarking shall:
- Be located on top of the roof framing, except that the roof battens may be fixed above the sarking
- Cover the entire roof area including ridges and hips; and
- Extend into gutters and valleys.
4.2 BAL-12.5 – BAL-40 Metal Roof
For compliance in BAL-12.5 to BAL-40 areas, metal sheet roofs shall:
- Be fully sarked, except that foil-backed insulation blankets may be installed over the battens; (Use Thermoseal Resiwrap or Anticon™, refer to Figure 4.2.1.b) or
- Have any gaps (such as under corrugations or ribs of sheet roofing and between roof components) sealed at the fascia or wall line and at valleys, hips and ridges using Bradford Multitel™ BAL12.5 – 40. Refer to Brochure for Figure 4.2.1.c.
- Refer to Brochure for more detailed information
4.3 BAL FZ Tiled Roofs
For BAL-FZ areas, much more stringent fire protection measures apply. In these areas the roofing system must comply with AS 1530.8.2 when tested from the outside.
The roofing systems detailed in this section have been assessed by a registered testing authority as being likely to achieve bushfire attack level BAL–FZ if tested in accordance with AS1530.8.2-2007.
4.4 BAL–FZ Metal Roof
For Metal roofs in BAL-FZ areas, there are 2 methods for Deemed-To-Satisfy compliance:
- AS3959 Construction of buildings in bushfire – prone areas
- National Association of Steel Framed Housing (NASH) Standard for Steel Framed Construction in Bushfire Areas
- Refer to Brochure for more detailed information
5.0 Bradford insulation products for bushfire roofing systems
Anticon foil faced metal roofing blanket
Anticon roofing blanket is a lightweight insulation with a light duty reflective Thermofoil facing. It is designed to provide effective condensation control and thermal and acoustic benefits.
Anticon is approved by the National Asthma Council’s Sensitive Choice® program and is suitable for use in homes of people with asthma or allergies.
Multitel BAL 12.5 – 40 Blanket
A non-combustible glasswool roll used to seal off areas of metal roofs from potential ember ingress. The blanket is typically installed at gutter line, hip valley and ridge joint.
Thermoseal™ Roof Tile Range
Bradford Thermoseal Roof Tile comprises a range of economical, heavy duty pliable reflective sarking membranes that are ideal for use under cement and terracotta roof tiles.
Manufactured from aluminium foil faced woven polymeric fabric, they have high tensile strength and tear resistance. They are suitable for use for ember protection in bushfire prone areas.
Enviroseal™ HTS - Vapour Permeable Roof Sarking Range
Enviroseal HTS is a highly durable, high water hold-out vapour permeable roof underlay for tiled, slate and metal roofs, and meets AS/NZS4200.1 requirement for classification as a medium duty membrane.
Enviroseal HTS minimises the risk of condensation by allowing internal moisture to escape, and can act as a tough weather barrier to help prevent rain damage in roofs.
Thermoseal™ 753 Heady Duty Sarking for Metal Roof
Bradford Thermoseal Heavy Duty sarking is a high vapour barrier reflective sarking with enhanced puncture and wind-flap resistance.
Specifically designed for use under metal roofs in dwellings, it helps reduce temperature variation in the roof space and protects against the ingress of embers in the event of a fire.
Fireseal FZ
Bradford Fireseal FZ is a fire rated rockwool insulation suitable for continuous operation in extreme temperature.
Specifically designed for use in tiled and metal roofs to help prevent the ingress of embers and flames into the roof space in the event of a fire.
Building in a Bush fire Area?
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6.0 Bradford insulation products for bushfire roofing systems
Maestro BAL – CSIRO assessed as AS 3959 compliant Maestro BAL™ powered by Bradford Air iQ, is a quality powered ventilator specifically designed to meet the requirements of AS3959 in areas up to and including BAL-40.
Why do you need a Bushfire rated ventilation system?
Roof ventilation is extremely important in bushfire prone areas, to reduce heat in the roof space through ventilation whilst being well sealed and protecting against ember ingress.
The standard for construction in bushfire zones requires that the roof space be well sealed, protecting against the risk of windblown embers entering and causing a fire that could threaten the home and occupants.
Maestro BAL features a stainless steel ember guard with 1.9mm aperture and a high efficiency motor that effectively ventilates your roof space while protecting your home and your family in the event of a bushfire.
Proper roof ventilation requires good airflow, allowing air to enter the roof space as well as exhaust from the same area.
To do this in a BAL40 region, CSR Bradford recommends the installation of 2 Metal Eave Vents per Maestro BAL.
7.0 Health & Safety
Glasswool & Rockwool insulation products are excellent insulation materials and are safe to use under all conditions. Insulation materials have been in worldwide use for over 70 years, and during that time their manufacture and use have been extensively monitored and researched.
CSR Bradford Glasswool & Rockwool products are manufactured using the latest FBS-1 technology, which are classified as Non-Hazardous.
Detailed information on health & safety is contained in the SUIS & ICANZ (Safe Use Information Sheet & Insulation Council of Australian & New Zealand) literature available from our website: www.bradfordinsulation.com.au.
8.0 Product Warranty
CSR Building Products Limited warrants CSR Bradford products to be free of defects in materials and manufacture.
CSR Bradford bulk insulation and foil faced products should not come into contact with water or be used in external applications or alkaline environments.
Need An Onsite Quotation?
If you're not sure where to start, or you'd just like a bit more advice, then talk to the experts at No.1 Roofing and Building Supplies; we can help you build the best bush fire rated property, to give you that piece of mind.
