Steel or Timber Roof Trusses? Why Steel is the Better Choice for WA Builds

Roof trusses influence structural performance, compliance, and long-term risk, not just upfront cost.

In Western Australia, termite pressure, bushfire ratings, coastal exposure, heat variation, and cyclonic conditions in the north often make timber a higher-obligation option over time.

Below, we explain why light gauge steel trusses are the better choice for most WA builds — residential and commercial.

Key Summary

• Termites: Steel is listed under NCC 2022 as a material not subject to termite attack. Timber trusses in WA’s risk zones require a compliant barrier system, ongoing inspections and long-term maintenance (AS 3660.1:2014).
• Bushfire: Steel is non-combustible. As BAL ratings rise across WA, the compliance pathway for timber trusses narrows significantly. Steel trusses can simplify parts of the BAL pathway because the roof framing is non-combustible, but overall BAL compliance still depends on the full roof system and detailing (AS 3959:2018).
• Dimensional stability: Timber moves with heat and humidity. In WA’s climate, this affects roofline geometry, ceiling tolerances and weatherproofing over time. Steel holds its shape.
• Structural performance: Steel trusses carry more load across longer spans with a lighter profile — without the engineered timber products timber needs to keep up.
• Cyclonic regions: For the Pilbara, Kimberley and Gascoyne, steel trusses engineered under AS 4600 perform consistently across wind classifications C1–C3.
• Maintenance: Steel trusses do not rot, do not absorb moisture and require no chemical treatment. The maintenance burden over the life of the building is materially lower than timber.

Reasons Why Steel is the Better Choice for Roof Trusses Over Timber

1. Termite Risk: A Compliance Obligation, Not Just a Maintenance Concern

Western Australia carries active termite risk across most of the state — higher in the north, but present across Perth metro and the south-west too. For timber roof trusses, that risk creates a compliance obligation that runs for the life of the building.

Under NCC 2022 Housing Provisions Part 3.4 (Termite Risk Management), termite protection is required when a building includes primary building elements that are susceptible to termite attack.

Standard timber is considered susceptible, while steel framing is listed as not subject to termite attack. In practical terms, timber roof trusses often introduce an ongoing termite management obligation, while steel removes termite susceptibility for the truss framing itself.

For timber trusses in a WA termite-risk area, that means:

• A compliant physical or chemical termite barrier installed during construction
• A permanent durable notice fixed to the building detailing the system and inspection requirements
• Ongoing annual inspections aligned to the installed system
• Maintenance or replenishment of chemical reticulation over time

Termite damage is commonly excluded from standard home insurance policies unless you have specific cover. Always check your Product Disclosure Statement (PDS) to confirm what is and is not included.

Repair costs for structural termite damage can be significant — and the hardest part is that it often occurs in roof spaces where it is not visible until it is serious.

Steel roof trusses remove termite susceptibility from the truss framing itself. Depending on the rest of the design, termite management may still apply to other susceptible elements, but steel takes the roof truss structure out of the termite risk category.

2. Bushfire Zones: The Case for Non-Combustible Trusses

WA has extensive bushfire-prone land. The Perth Hills, the south-west, the Great Southern and many regional areas include zones where development is subject to a Bushfire Attack Level (BAL) rating under AS 3959:2018.

As that rating rises, the compliance pathway for timber trusses gets progressively harder.

Steel trusses are non-combustible, which is a strong advantage in bushfire-prone areas. Using non-combustible roof framing can simplify parts of the BAL pathway, because you are not relying on timber performance or timber treatments for the roof structure.

That said, BAL compliance is always about the full roof system and detailing, including ember protection, vents, junctions and gaps. Steel reduces the combustible load in the roof, but the rest of the bushfire detailing still matters.

On many bushfire-rated projects, timber starts to look less attractive once you factor in the extra detailing, material choices and risk management that can come with higher BAL requirements. For that reason, steel is frequently considered early for BAL-rated sites, especially as the BAL level increases.

3. Dimensional Stability: Steel Stays True, Timber Doesn’t

Timber absorbs and releases moisture as temperature and humidity change. In WA, where summers regularly exceed 40°C across much of the state and coastal areas experience meaningful humidity cycling, that movement matters at roof level.

What movement looks like in timber trusses:

• Bow or camber changes in chord members that affect roofline geometry and sheeting tolerances
• Connection loosening where nailed plates seat into shrinking or softening timber
• Differential movement between trusses causing unevenness in ceiling and roofing planes
• Truss creep under sustained load, amplified by moisture cycling over WA summers

For standard residential builds, this is often managed with care and experience. But for larger spans, modular builds, multi-residential projects or prefabricated panels — all growing sectors in WA — dimensional variability in timber compounds with scale and creates real quality risk.

Light gauge steel trusses are dimensionally stable. The geometry that leaves the factory stays in service. That consistency matters most when tolerances are tight and the cost of rectification is high.

4. Structural Performance: Stronger Spans, Lighter Profile

The structural case for steel becomes more compelling as span requirements increase and loading demands rise. Steel trusses offer a higher strength-to-weight ratio than equivalent timber, which means they achieve more with less material.

Where steel clearly outperforms timber:

• Larger clear spans (often 12m and above, depending on the design and loads), where timber typically needs deeper sections, multiple members, or engineered products such as LVL or glulam
• Higher imposed loads in commercial applications — retail, industrial, childcare, multi-residential
• Cyclonic wind regions: the Pilbara, Kimberley and Gascoyne, where roof structures must meet wind classifications C1–C3. Steel trusses designed under AS 4600:2018 handle these conditions with engineered connection systems built into the truss package — not specified separately in the field

For remote and regional WA projects, where getting the roof structure right the first time is not optional, that level of engineered certainty has value beyond the purely structural.

5. Long-Term Maintenance: The Cost Nobody Factors Into the Initial Quote

The upfront cost comparison between timber and steel trusses does not capture what happens over the life of the building. Timber carries an ongoing maintenance burden that is easy to underestimate at the decision stage.

For residential builds:

• Termite barrier systems require inspection and, where chemical reticulation is used, periodic replenishment
• Coastal salt air in Perth beachside suburbs and along the WA coast accelerates surface degradation of exposed timber elements
• Movement-related issues — cracking at ceiling junctions, roofline irregularities — require investigation and rectification

For commercial builds:

• Larger roof areas and more difficult access mean issues can develop before they are detected
• In childcare, health care and food production environments, deteriorating timber surfaces in accessible roof spaces create hygiene and asset management issues on top of the structural ones

Steel roof trusses do not rot, do not require chemical treatment, and are not susceptible to insect attack. In galvanised form, they perform reliably in WA’s coastal and high-humidity environments. The maintenance obligation over the building’s life is materially lower.

Steel vs Timber Roof Trusses: At a Glance

Is Timber Ever the Right Choice?

Yes. Timber trusses are not inherently unsuitable, and for certain projects they remain a practical option.

Timber may still make sense where:

• BAL rating is low, and termite management requirements are clearly addressed for any susceptible elements
• Spans are standard (under 10–12m) and loads are straightforward
• Budget is the primary constraint and long-term maintenance costs are accepted
• The build is a simple outbuilding or secondary structure with lower compliance obligations

But for most residential builds in Perth, regional WA or anywhere with termite risk, bushfire exposure or coastal conditions — and for virtually all commercial projects — the full cost of timber, compliance, treatment, inspection, risk, and maintenance needs to be weighed honestly against steel’s higher upfront material cost.

In most WA conditions, that comparison is closer than the initial quote suggests.

Why Choose Steel and Steel Frames WA for Your Roof Trusses

At Steel Frames WA, we manufacture and supply precision light gauge steel roof trusses for residential and commercial projects across Western Australia — including remote and regional delivery to the Pilbara, Kimberley, Gascoyne and south-west.

What we offer:

• Trusses engineered to WA’s wind and climate conditions, including cyclonic classifications
• Manufactured using FrameCAD technology for precision and consistency
• Full service: design, manufacture, supply and installation
• Over 50 years of building expertise in WA — we understand local termite, bushfire, coastal and soil conditions
• Remote delivery capability across WA — if your site is outside Perth, we can handle it

If you are planning a project and want to understand how steel roof trusses would work for your site and budget, get in touch with our team today.

FAQs

Are steel or timber roof trusses better for Western Australian conditions?

Steel roof trusses are often better suited to Western Australian conditions because they are not susceptible to termites, do not rot, and remain dimensionally stable through changes in heat and humidity. Steel can also provide advantages in bushfire-prone, coastal and cyclonic areas, although the best option will depend on the project’s design, location and compliance requirements.

How do steel and timber roof trusses compare for termite resistance?

Timber roof trusses can require termite management measures such as compliant barriers, inspections and ongoing maintenance where susceptible structural elements are used. Steel roof trusses are not subject to termite attack, removing the truss framing itself from this risk. Other susceptible parts of the building may still require termite protection.

Are steel roof trusses better for bushfire and cyclonic areas?

Steel roof trusses are non-combustible, which can provide advantages for projects in bushfire-prone areas. They can also be engineered for the high wind loads experienced in cyclonic regions of Western Australia. However, bushfire and cyclone compliance depends on the design of the complete building and roof system, not the trusses alone.

Do steel roof trusses require less maintenance than timber trusses?

Generally, yes. Timber can be affected by termites, moisture, movement and deterioration over time, while steel trusses do not rot, absorb moisture or require chemical termite treatment. This can reduce some of the ongoing inspection, treatment and maintenance requirements associated with the roof structure.

When might timber roof trusses still be suitable?

Timber roof trusses can still be a practical option for straightforward residential projects with standard spans, lower exposure risks and appropriate termite management. For larger spans, commercial buildings or projects exposed to termites, bushfire or cyclonic winds, steel roof trusses may offer greater long-term advantages.

Are steel roof trusses more expensive than timber roof trusses?

The upfront cost of steel and timber roof trusses varies depending on the building design, spans, engineering requirements, material prices and installation. Timber can be economical for standard residential construction, while steel may become more cost-effective where longer spans, complex roof designs, reduced maintenance or additional durability are important. The total lifecycle cost should therefore be considered rather than comparing material prices alone.

How long do steel roof trusses last compared with timber trusses?

Both steel and timber trusses can provide a long service life when correctly designed, installed and maintained. Steel has the advantage of not being affected by termites, rot, warping or moisture absorption. Appropriate corrosion protection is important, particularly in coastal environments, while timber requires suitable protection from moisture and pests.

Can steel roof trusses span further than timber trusses?

Steel roof trusses can be engineered for long clear spans while maintaining a relatively lightweight structure. This makes them well suited to commercial buildings, warehouses, sheds and residential designs where large open spaces or fewer internal supports are required. The achievable span ultimately depends on the truss profile, loads, building design and structural engineering requirements.