Composite decking fire ratings and BAL zones in Australia

If your block has a Bushfire Attack Level, the deck is part of the build that has to meet it. A composite board on its own doesn't carry a fire rating for your deck. The makers tie each rating to the way the whole deck is built. The subframe and the gap between boards are part of it. Several composite brands state BAL-29 for their boards and one states BAL-40. Below BAL-29 there are plenty of choices. Above it, only one of the brands checked here states a rating. At that end the frame and the detailing matter as much as the board.

What does fire rated decking actually mean?

A Bushfire Attack Level measures how severe a building's exposure to a fire could be, expressed in steps of radiant heat in kilowatts per square metre. The levels run from BAL-LOW through BAL-12.5, BAL-19, BAL-29 and BAL-40 to BAL-FZ, and in Victoria's Bushfire Management Overlay BAL-LOW does not apply⁵. CSIRO describes BAL-12.5 as radiant heat up to 12.5 kW/m² and BAL-29 as radiant heat up to 29 kW/m²⁴. At BAL-40 the radiant heat runs up to 40 kW/m² and flames may intermittently contact the house, and at BAL-FZ the heat goes beyond that and flames are likely to engulf part or all of it⁴. The number on your BAL certificate is the one your deck has to answer to.

The construction rules for each level sit in AS 3959, Construction of buildings in bushfire-prone areas, published by Standards Australia in November 2018². The NCC calls that standard up for houses. Its deemed-to-satisfy route for a house in a designated bushfire-prone area, and for a deck associated with it, is to build to AS 3959 or to the NASH steel-framing standard for bushfire areas¹. A detached deck can be caught too. In New South Wales, the Rural Fire Service says some detached structures, such as sheds and decks, within 6 m of a building on bushfire-prone land also have to meet its planning rules³.

So a fire rated deck board is one the maker has had certified at one of the levels above. Three of the makers below name the test behind their rating, AS 1530.8.1, on their own pages or fixing sheets⁷. The makers also tie a rating to the way the deck is built. One says fire ratings are not absolute values for a product but apply to how it's installed and the building system it's part of¹⁶. Another certifies its board only with the subframe it specifies. The joists under the board and the gap between boards count as much as the board.

Which brands publish ratings, and to what level

I'd keep this at brand level and read the brand's own page before you buy, because ranges and conditions change.

ModWood states the highest level among the brand pages checked here. Its Flame Shield range is described on its own page as tested and certified under AS 3959-2018 for use from BAL-12.5 up to and including BAL-40, with either an enclosed or unenclosed subfloor⁶. The fixing instructions for that range add a condition: the joists and bearers must be non-combustible or one of the bushfire-resisting timbers listed in the standard's appendix⁷. They also say each board carries an ink-jet message along its edge with the rating and the test standard, to be sighted on every board before it's installed⁷.

Ekodeck sells a Flame Fighter range described as tested to AS 1530.8.1:2018 and certified BAL-29, for bushfire-prone areas up to and including that level⁸. Its Designer Series page says the Designer and Summit Series are now certified BAL-29 as well⁹.

Futurewood has a BAL 29 decking page that lists BAL-LOW, BAL-12.5, BAL-19 and BAL-29 as the levels its product suits, and its menu describes the CleverDeck Xtreme board as BAL-29 decking¹⁰. The same page spells out the construction side. For BAL-29 it wants non-combustible or bushfire-resistant timber supports where the subfloor is unenclosed, and it advises the minimum board gap allowed so embers have less room to lodge¹⁰.

Brite says all of its NextGen Titanium boards are BAL-29 certified and that BAL-29 options in its HD Pro range are available on request, citing AS 1530.8.1:2018 and AS 1530.4:2014¹¹.

TimberTech, sold here through James Hardie, is described as engineered to meet requirements for BAL-29 areas, with the note that suitability depends on the site, the application and the required BAL¹².

The current NewTechWood brochure has a "BAL 29 Rated" column in its decking table, marked yes for each decking board and no for the fascia board¹⁵. Its FAQ, answering a question about cladding, says a fire rating depends on the installation and the building system rather than the product alone. Trex lists a 2019 bushfire testing report for its Transcend range on its Australian downloads page, and that's the document to read for its levels and conditions¹⁴.

The highest level on any of these brand pages is BAL-40, so a BAL-FZ deck is beyond what these composite boards claim. In New South Wales, the NCC's deemed-to-satisfy route leaves out the BAL-FZ section of AS 3959, and a BAL-FZ build has to meet the specific conditions of its development consent instead¹. At that level I'd talk to the certifier and an engineer before choosing any board.

The subframe and the gaps are part of the rating

Every one of those ratings comes with conditions, and I'd read them before pricing anything. A BAL-40 board laid on treated pine joists is not a BAL-40 deck, because the fixing instructions for that board require non-combustible joists and bearers or one of the listed bushfire-resisting timbers. Another maker's page asks for non-combustible or bushfire-resistant timber supports at BAL-29 wherever the subfloor is unenclosed. A steel frame is non-combustible, so it answers that question outright. There's more in steel framing, in the guide on steel versus timber frames and in the guide on aluminium deck framing.

The gap between boards is the other condition. One maker's page notes that typical board gaps run from 2 mm to 6 mm and advises the minimum spacing allowed, to reduce the risk of burning embers lodging between boards¹⁰. That cuts against the wider gap asked for on some low decks over concrete, which is there for ventilation, as the over-concrete guide explains. On a bush block I'd follow the ember advice and get the airflow another way, by keeping the frame off the ground and the subfloor clear so the narrower gap doesn't trap water. Composite also expands in heat and contracts in the cold. The end gaps still have to be right, and the guide on expansion gaps covers that.

I'd treat a stair off a rated deck as part of the deck and build its stringers and treads from materials that suit the BAL. One Bunnings Workshop member, BoeingFan, asked in July 2025 how to build steps from a deck and, being in a bushfire-prone zone, wanted to avoid pine where possible²⁰. The replies moved to metal stringers on a concrete footing with merbau treads, which one reply said would suit bushfire areas better. That's the right instinct, and the framing side is in the guide on composite decking stairs.

What owners on bush blocks run into

The thread that shows the shopping problem most clearly is from Whirlpool in May 2023. FNQ-Bill wrote "I need pool decking in a bushfire area in FNQ" and was after a BAL-29 board that wouldn't fade or scratch easily¹⁷. The same post said one brand seemed to offer only BAL-40 and not BAL-29. I'd correct that reading for the range in question, because its own page states it for BAL-12.5 up to and including BAL-40⁶.

The reply, from LTDedition, was about a sister in a bushfire-prone area who had used a fibre-cement deck system about six years earlier. The post said the deck still looked good, had beaten the cockatoos that shredded her old timber deck, and had a BAL-FZ rating¹⁷. The maker's decking page today lists that system for bushfire-prone areas up to BAL-29 certification¹³. It's a good example of why I'd check the maker's own page rather than a forum post.

The other thread worth reading is from April 2017. The owner, b0son, was planning a deck around a pool at BAL-19 and understood that an enclosed subfloor allowed any timber, while an unenclosed one needed fire-resistant species¹⁸. A reply from adavis worked from the 2009 edition of AS 3959, allowing that it might have been superseded. On that reading the standard didn't set special construction requirements for deck supports or framing at BAL-19, and bushfire-resisting timbers only came in at BAL-29. The owner then said the certifier's summary sheet behind that understanding was clearly wrong. Other replies said to go steel, and adavis added that for anything well off the ground it would be steel only, with an 80 m² deck rated BAL-FZ then under way all in steel¹⁸.

The lesson I'd take from that thread is to read the deck clauses for your own level in the current edition, or have your certifier point to them, rather than rely on a summary. My advice matches the thread's other point: let the BAL decide the frame first, then choose the board.

On ProductReview, a ModWood owner in New South Wales, Osiris, gave five stars about four years ago and wrote that the deck "reduces fire risk (we are in a fire prone area)"¹⁹. That's the kind of claim I'd want paperwork for, which is where the last section comes in.

What I'd have ready for the certifier

I'd start with the BAL assessment for the site, because nothing else makes sense without it. Then the maker's test certificate, or the page that states the level and the standard, printed, with the range name matching the boards on the pallet. For a range that prints the rating along the board edge, the maker asks for that message to be sighted on every board before installation, so I'd photograph a few edges before they go down. I'd have the subframe material on the plan, whether steel, aluminium or a hardwood from the standard's list, with the fixings. Write the board gap down, and show the subfloor as enclosed or open with the supports to suit. In New South Wales, if a detached deck is within 6 m of the house on bushfire-prone land, I'd assume it's in scope³.

Before you order

Get the BAL certificate first and read the deck clauses of AS 3959 for that level, or have your certifier walk you through them. Pick the board from the brands that publish a rating at or above your level, then read that brand's conditions for the frame and the gap before you price anything. If the subfloor will be open, I'd decide on steel or a listed hardwood for the frame. If the deck runs around a pool, the pool decking guide covers the fence and the fixings. The deck designer will lay out the joists and give you a materials list as a concept plan, and your certifier checks that plan against the standard.