For owners of warehouses, factories, commercial buildings and other industrial assets across Australia, an ageing corrugated steel roof can become a significant maintenance concern.
What may start as surface rust, fading or minor leaks can eventually develop into widespread corrosion, coating failure and deterioration of the roofing system. At that point, asset owners often face an important question:
Should the existing roof be rehabilitated, or is complete replacement the better option?
The answer is not always straightforward.
Roof replacement may provide a completely new roofing system, but it can also involve significant material, labour, access, disposal and operational costs. Depending on the building and the condition of the existing roof, rehabilitation may provide another option by repairing suitable areas and applying a protective coating system to extend the service life of the existing asset.
For Australian asset owners and roofing applicators, the important first step is to understand the condition of the existing roof and whether rehabilitation is technically feasible.
Corrugated steel roofing is commonly used across industrial, commercial and agricultural buildings because it is relatively lightweight, practical and durable. However, like other exposed steel assets, it remains vulnerable to moisture and environmental exposure.
Australian conditions can be particularly demanding.
Roofs can experience:
When the protective coating on steel deteriorates, moisture can reach the underlying metal. Corrosion can then progress beneath or around the damaged coating.
For asset owners, the problem isn’t simply that the roof looks old.
Corrosion can become an asset-management issue.
Early identification can give asset owners more options.
Some signs that a corrugated steel roof may require assessment include:
Small areas of surface rust may indicate that the existing protective coating is breaking down.
If rust has developed across large areas of the roof, a more detailed inspection may be necessary to determine the extent of deterioration.
A failing coating system can expose the underlying steel to moisture and environmental conditions.
Fasteners, laps and penetrations can become vulnerable points where moisture enters or corrosion develops.
Leaks can indicate deterioration of the roof sheet, joints, penetrations, flashings or other components.
This is particularly important.
Surface rust is different from significant metal loss. If corrosion has substantially reduced the thickness or structural capacity of the roofing material, coating alone may not be an appropriate solution.
Bent, severely deteriorated or structurally compromised sheets may require repair or replacement rather than simply being recoated.
When an ageing roof reaches the point where significant work is required, there are generally two broad approaches:
Rehabilitation involves retaining suitable parts of the existing roofing system, carrying out necessary repairs and applying a protective system to extend its service life.
Replacement involves removing the existing roof and installing a new roofing system.
Neither approach is automatically appropriate for every building.
The decision should be based on the condition of the existing asset, structural requirements, corrosion severity, project objectives and expected service life.
Roof rehabilitation may be worth investigating when the existing roof remains fundamentally suitable for continued service but is experiencing surface deterioration, corrosion or coating breakdown.
Potential indicators include:
Before considering a coating system, the condition of the roof structure and roofing sheets should be assessed.
Safe Work Australia guidance for work on existing roofs highlights the importance of checking roof strength and identifying fragile areas and corrosion before commencing work.
Where corrosion is primarily surface-level or limited to areas that can be appropriately repaired and prepared, a protective coating system may be considered.
Coatings rely on suitable surface preparation and adhesion.
Rust, scale, contamination, loose coating and other unsuitable material generally need to be addressed before coating.
If the objective is to extend the useful life of an existing roof rather than immediately replace it, rehabilitation may warrant investigation.
Large industrial and commercial buildings can be difficult to shut down for major roof replacement.
Depending on the site, roof rehabilitation may reduce the scope of removal and replacement work.
Roof rehabilitation is not a solution for every deteriorated roof.
Replacement may be more appropriate when:
This is why an inspection should come before selecting a coating system.
The first question should not be “Which coating should we use?”
It should be:
“Is this roof suitable for rehabilitation?”
Where an existing corrugated steel roof remains structurally suitable for continued service, but corrosion and coating deterioration are affecting the asset, we recommend first assessing the roof condition and completing the required surface preparation and repairs.
For exposed steel where an anti-corrosion base coat and UV-resistant protective finish are appropriate, a Liquimix system can consist of:
1. Surface preparation
The surface preparation for the steel must conform to the following requirements.
2. Metalox-GC450 – Anti-corrosion base coat
Apply Metalox-GC450 to the suitably prepared steel substrate as the protective anti-corrosion base coat.
3. Opalon-S30 – UV-resistant topcoat
Apply Opalon-S30 as the protective finish where UV resistance and weather exposure are important.
Prepared steel → Metalox-GC450 → Opalon-S30
The final specification should be confirmed based on the roof condition, existing coating, corrosion severity, environmental exposure and project requirements.
Before committing to either option, asset owners should consider the following.
How much corrosion is present?
Is the corrosion superficial, localised or widespread?
Can the existing roof safely remain in service?
This should be assessed by an appropriately qualified professional where required.
How much useful life remains in the existing roof?
Compare the total project costs—not simply the price of coating versus new roofing sheets.
Consider:
Will the building need to be partially or completely shut down?
For warehouses, factories and operational facilities, disruption can be a major consideration.
Is the building:
These conditions influence coating selection and expected performance.
A rehabilitation project should be considered part of an ongoing asset-management strategy rather than a one-time cosmetic repair.
For ageing corrugated steel roofs, replacement is not always the only option. Where the existing roof remains structurally suitable and corrosion or coating deterioration can be properly addressed, rehabilitation may provide a practical way to extend the service life of the existing asset.
The key is to assess the roof before selecting a solution. The extent of corrosion, structural condition, substrate, environmental exposure and project requirements should all be considered when deciding between rehabilitation and replacement.
Where rehabilitation is suitable, a properly prepared substrate and the right protective coating system can help protect exposed steel from further environmental deterioration.
Recommended system:
Prepared steel → Metalox-GC450 → Opalon-S30
For project-specific requirements, the final coating system should be selected based on the condition and exposure of the existing asset.
If you are assessing an ageing or corroded steel roof and are unsure whether rehabilitation or replacement is the right approach, contact Liquimix to discuss your project requirements and coating options.
📞 1300 123 085
🌐 liquimix.com
