BAL-40 Windows & Doors Perth | Built for Flame-Zone-Adjacent Sites

BAL-40 (Bushfire Attack Level 40) is the second-highest rating in the six-level AS 3959 scale and the most demanding level at which standard residential construction can proceed. It represents a radiant heat exposure band of 29 to 40 kW/m2 at which flame contact is considered likely during a bushfire, whereas at BAL-29 flame contact is not expected. A BAL assessment must be conducted by a BPAD-accredited assessor (a certified Bushfire Practitioner, Level 1 or higher) before a building permit is issued for any property within a DFES-designated bushfire prone area in Western Australia. The assessor evaluates four inputs: the Fire Danger Index for your region, the classified vegetation type under AS 3959 categories, the measured distance from the proposed building to that vegetation, and the land slope. Where steep slopes on the Darling Scarp combine with dense native bush in suburbs such as Mundaring, Kalamunda, Lesmurdie or Serpentine-Jarrahdale, BAL-40 outcomes are common. The result is recorded in a BAL Assessment Report and submitted with the building permit application.

The AS 3959 Section 8 minimum for BAL-40 windows is 6mm toughened safety glass as the fire-exposed outer pane, a step up from the 5mm toughened minimum at BAL-29. Glazed doors at BAL-40 also require 6mm toughened glass minimum. Float glass and laminated glass alone are not suitable as the primary outer pane for single-glazed BAL-40 windows under the deemed-to-satisfy pathway. In double-glazed configurations using the tested system pathway under AS 1530.8.1, the inner pane may use toughened or laminated glass depending on the certified assembly. Using a double-glazed insulated unit with a 6mm toughened outer pane also provides superior thermal protection compared to single glazing, because the sealed air gap reduces heat transfer to the interior of the building.

Aluminium mesh is not permitted at BAL-40 or BAL-FZ because the likely flame contact and higher thermal exposure at this level means aluminium cannot reliably maintain screen integrity during a fire event. AS 3959 Section 8 specifies that ember protection screens at BAL-40 must be fabricated from corrosion-resistant steel or bronze mesh or perforated sheet with a maximum aperture of 2mm. Aluminium mesh is accepted at BAL-29 and lower levels. The screen frame must also be metal, and perimeter gaps around the screen assembly must not exceed 3mm to prevent ember entry through the gap between the screen and the building element.

Shutters are not a blanket requirement at BAL-40. Three compliance pathways exist under AS 3959, and two of them do not require shutters at all. First, a window or door system tested and certified to AS 1530.8.1 at BAL-40 satisfies Section 8 as a complete tested assembly without separate shutters. Second, the deemed-to-satisfy pathway uses 6mm toughened glass, metal frames, and corrosion-resistant steel or bronze screens to achieve compliance without shutters. Third, non-compliant glazing can be fully protected by external bushfire shutters made from non-combustible material; combustible shutters acceptable at lower BAL levels are not permitted at BAL-40. Most buyers select either a tested system or the DTS pathway with screens. The tested system pathway is often preferred because screening is only required on the sections that open, not across the entire glazed face.

Yes. Double-glazed insulated units can be certified for BAL-40 compliance via the tested system pathway under AS 1530.8.1, and double glazing at BAL-40 adds year-round thermal performance to the bushfire rating. The fire-exposed outer pane must be 6mm toughened glass; the inner pane of the insulated unit may be toughened or laminated glass depending on the specific certified assembly. A thermally broken aluminium frame combined with a double-glazed insulated unit can simultaneously satisfy AS 3959 Section 8 requirements and deliver high thermal performance, reducing heating and cooling loads year-round. Insulated glass assemblies also provide superior bushfire thermal performance compared to single glazing, because the sealed air gap reduces heat transfer to the interior face of the window.

The three key technical changes from BAL-29 to BAL-40 are: window glazing increases from 5mm toughened minimum to 6mm toughened minimum; ember screens must upgrade from aluminium mesh (permitted at BAL-29) to corrosion-resistant steel or bronze mesh; and metal frames become a DTS requirement rather than simply a preferred option. Cost differences arise from those three factors: thicker glass in window units, the screen material upgrade from aluminium to steel or bronze, and any additional certification work for tested systems. No verified price comparison data exists for Western Australian projects; ask for an itemised quote noting the BAL level for each window and door opening to see the direct difference for your specific schedule.

The AS 3959 Section 8 requirement for the fire-exposed outer pane at BAL-40 is 6mm toughened safety glass. Laminated glass alone is not suitable as the primary outer pane in a single-glazed BAL-40 application under the deemed-to-satisfy pathway. In double-glazed configurations using the tested system pathway under AS 1530.8.1, the inner pane may use laminated glass in some certified assemblies, which can improve acoustic performance. Double-glazed insulated units provide better bushfire thermal performance than single glazing because the sealed air gap reduces the heat transferred to the interior face of the glazed opening, making the interior pane less vulnerable to thermal shock. Your compliance documentation will specify the exact glass configuration used in the certified assembly installed on your project.

Yes. Sliding doors can be installed at BAL-40 subject to the AS 3959 Section 8 requirements. Glazed door panels require 6mm toughened glass minimum and frames must be metal throughout. Sliding doors must be tight-fitting in the frame to prevent ember entry through gaps. Screen protection using corrosion-resistant steel or bronze mesh with a maximum 2mm aperture must be applied as screen doors or screens face-fixed to the glazed door panels. Door frames must be metal throughout. The NCC references AS 3959 clauses 8.5.1, 8.5.1A, 8.5.3 and 8.5.4 for the detailed requirements covering door seals, weather strips, thresholds and hardware at BAL-40. Tested BAL-40 door systems certified to AS 1530.8.1 satisfy the Building Code of Australia requirements as a tested assembly and do not require additional screening under that pathway.

The compliance package for BAL-40 windows and doors in Western Australia includes: manufacturer test reports citing AS 1530.8.1 certification at BAL-40 or higher; AGWA (Australian Glass and Window Association) compliance certificates; a product adhesive label on each unit identifying it as a certified BAL-40 assembly; and installation records confirming the system is installed exactly as tested and certified, including frame fixings, screen assemblies, and any specified seals or hardware. This documentation package is required for building permit sign-off and is the record your insurer needs to confirm glazed openings meet the construction standard for your designated bushfire prone area. Penot provides the documentation set as a standard part of every BAL-40 supply and installation.

Yes, but full window and door replacement with certified BAL-40 assemblies is required. Replacing only the glass in an existing non-BAL-40 frame does not produce a certified BAL-40 system, because the tested system pathway requires the complete assembly (frame, glazing, hardware, seals, and screens) to be installed exactly as it was tested and certified. You cannot achieve compliance by upgrading individual components of an existing uncertified frame. Full window and door replacement is the correct approach, and the work must be carried out in accordance with the building permit requirements for your assessed BAL-40 site. Call Penot Double Glazing on 1300 121 603 to discuss your existing home and the window and door schedule your BAL-40 assessment requires.