Is TRUECORE® steel AZ150 or AM150?

BlueScope's current TRUECORE® steel G550 data sheet lists AM150 as the normal supply coating class. AM is an aluminium, zinc and magnesium alloy coating.

Does Lockyer Sheds give a 50-year warranty?

No. The TRUECORE® frame warranty is offered by BlueScope, for up to 50 years on the whole house frame for eligible applicants, on BlueScope's terms. Lockyer Sheds can confirm the frame is made from TRUECORE® steel to support an application.

Can I get the TRUECORE® warranty near the beach?

Not within 300 metres of surf or exposed marine influences, according to BlueScope. Calm marine settings more than 5 metres from the high-water mark may be eligible. Check the current terms for your lot.

Is a TRUECORE® steel frame fire rated?

The steel is a non-combustible material. A fire-resistance level or bushfire compliance belongs to the whole wall, roof or building system, not to the frame alone.

Materials

TRUECORE® steel explained: grade, coating, fire indices and warranty

By Lockyer Sheds, Crowley Vale QLD ·Getting started · 8 min read · Published 26 September 2026

Short answer

TRUECORE® steel is BlueScope's metallic-coated steel for building frames. The G550 product has a guaranteed minimum yield strength of 550 MPa, is made to AS 1397:2021 and is normally supplied with an AM150 aluminium, zinc and magnesium coating. Lockyer Sheds roll-forms its frames from TRUECORE® steel. Any frame warranty is BlueScope's, offered for up to 50 years to eligible applicants on its own terms.

Illustrative image: galvanised steel strip running through a roll-forming machine to make framing members — Illustration, not a completed project

What TRUECORE® steel is

TRUECORE® steel is made by BlueScope and sold for light gauge steel framing: wall frames, roof trusses and floor systems. It arrives at a frame manufacturer as coil. The coil is uncoiled and fed through roll formers that cold-form the flat strip into framing sections. Lockyer Sheds does this at its factory in Crowley Vale, in the Lockyer Valley, and assembles the members into wall panels, trusses and floor components to the job's plans.

Grade, coating and standard

BlueScope's current data sheet for TRUECORE® steel G550 describes a hot-dipped, aluminium, zinc and magnesium alloy-coated structural steel with these properties:

TRUECORE® steel G550: properties published by BlueScope
Property	Published value	What it means for a frame
Grade	G550	Guaranteed minimum yield strength of 550 MPa
Standard	AS 1397:2021	The Australian standard for continuous hot-dip metallic coated steel sheet and strip
Coating class	AM150 (normal supply)	Aluminium, zinc and magnesium alloy coating that slows corrosion
Thickness range of the product	0.42 to 1.00 mm	The range BlueScope makes. The thickness used for each member comes from the frame design
Fire hazard indices (AS/NZS 1530.3)	Ignitability 0, spread of flame 0, heat evolved 0, smoke developed 0 to 1	A non-combustible material, not a fire-resistance level

Two points often get muddled online. First, the coating on current TRUECORE® steel is AM150, not AZ150. Second, the thickness range is the range of the steel product. It is not a statement of which base metal thickness goes into your studs or truss chords. That is set by the frame design for your plans and site.

Non-combustible, and what that does not mean

The NCC defines a non-combustible material as one that is not deemed combustible under AS 1530.1. BlueScope's data sheet states TRUECORE® steel may be used wherever a non-combustible material is required under NCC 2022. That is a useful property. It is not a fire-resistance level for a wall system, and a frame does not carry a bushfire attack level by itself. In bushfire-prone areas the building is designed to AS 3959 or to the NASH Standard for steel framed construction in bushfire areas, and the cladding, linings, glazing and roof all form part of that design.

Traceability

BlueScope says TRUECORE® steel is marked with the relevant standard, strength grade, base metal thickness, coating class and a unique identifier, and that test certificates can be made available on request. Those markings let the steel in a frame be traced back to its production.

How long does TRUECORE® steel last?

The coating slows corrosion. It does not make steel immune to it, and site conditions matter. BlueScope advises using the material within six months to avoid storage-related corrosion and describes its frame warranty in terms of life before corrosion leads to structural failure. The warranty terms are the best guide to the conditions BlueScope expects.

The TRUECORE® frame warranty

Note:The warranty is BlueScope's, not Lockyer Sheds'. Eligibility, terms and the application are handled by BlueScope. Read the current terms on the TRUECORE® website before relying on them.

According to BlueScope's warranty information for builders and home owners, the following may be available to eligible applicants:

Up to 50 years for the entire house frame in detached homes, townhouses and duplexes.
Up to 25 years for a subsystem only: roof trusses only, intermediate floors only, or wall frames only.
Commercial warranties of up to 25 years, on application.

Where the warranty is not available

BlueScope does not provide a TRUECORE® frame warranty within 300 metres of surf or exposed marine influences. It says a warranty may be available in calm marine settings such as canal estates and estuaries, more than 5 metres from the high-water mark. This matters for some beachside lots, so check before you plan around it.

Conditions in the sample warranty

BlueScope publishes a sample building frame warranty. The actual certificate governs, but the sample lists conditions including:

The frame must be separated from the external environment and from ground moisture. Homes with unlined eaves are excluded.
Steel in the subfloor space beneath a suspended floor is excluded.
On slab-on-ground homes, perimeter bottom plates need an impermeable barrier.
Plates, studs, noggings, chords and webs must all be TRUECORE® steel.
Fasteners must suit an ISO 9223 Category 3 environment.
Paint applied to the frame after manufacture voids the warranty.

How to apply

BlueScope's builder information says a builder can apply on the customer's behalf where installation is within the next 18 months, which generates an activation code. Home owners can register online after installation. We will tell you which parts of your frame are TRUECORE® steel so the application can be made, but we cannot issue or promise the warranty ourselves.

Looking after the steel on site

Most of what shortens the life of a coated steel frame happens on site or in the finished building, not in the factory. BlueScope's advice to use the material within six months is about storage-related corrosion, and the same thinking applies to a delivered kit: keep bundles off the ground, keep water from pooling in them and stand the frame reasonably soon after it arrives.

Store bundles on bearers clear of the ground, somewhere that drains.
Cover bundles against weather if the frame will sit for a while, and let air circulate.
Keep the frame separated from ground moisture once it is standing. The sample warranty asks for an impermeable barrier under perimeter bottom plates on slab-on-ground homes.
Do not paint the frame after manufacture. BlueScope's sample terms say post-applied paint voids the warranty.
Use fasteners suited to the environment. The sample terms name ISO 9223 Category 3.

Questions to ask any frame supplier

Which components of my frame are TRUECORE® steel? The sample warranty needs plates, studs, noggings, chords and webs to be TRUECORE® steel.
Is my site within 300 metres of surf or exposed marine influences?
Are the eaves on my design lined? Unlined eaves are excluded in the sample terms.
Who applies for the warranty, and when? BlueScope's builder process allows an application where installation is within the next 18 months.

Who makes TRUECORE® steel?

BlueScope makes TRUECORE® steel and owns the trade mark. Frame manufacturers such as Lockyer Sheds buy the coil and turn it into frames. The finished frame is our product, made to your plans. The steel and its warranty are BlueScope's.

Next step

If you want TRUECORE® steel frames for a Queensland or northern NSW job, send the plans. We will quote the frame and confirm which components are TRUECORE® steel for the warranty application.