Understanding Natural Weathering
All roofing materials are subject to natural weathering — a gradual change in appearance due to exposure to environmental elements such as sunlight, rain, wind, temperature fluctuations, and airborne pollutants. While this is completely normal, the extent and visibility of weathering depends on the type of coating used and the surrounding environment.
1. PVC Plastisol Coated Steel Roofing Sheets
PVC plastisol is a premium coating made from a thick, plastic-based layer applied over galvanised steel.
Known for its durability and resistance to environmental stressors, it’s a popular choice for long-term roofing and cladding performance — especially in demanding environments.
⚠️ PLEASE NOTE: If your building is located near the sea, PVC plastisol coating is strongly recommended, as plain galvanised and polyester coated sheets are more vulnerable to salt-laden air, which can accelerate corrosion and reduce lifespan.
Key weathering characteristics:
- UV Resistance: Outstanding UV resistance, maintaining colour and gloss longer than many alternatives.
- Durability: The thicker coating (typically 200 microns) provides excellent protection against corrosion, mechanical wear, and colour fade.
- Expected Lifespan: 30+ years depending on exposure, location, and upkeep.
Natural Weathering of PVC Plastisol Coated Sheets – What to Expect
Over time, PVC plastisol coated roofing sheets may develop watermarks or a visible ‘patterning’ effect on the surface. This is a normal and harmless part of the weathering process and should not be mistaken for damage or product failure.
✅ What Causes It?
These markings can occur due to:
- Moisture sitting on the surface during early exposure to rain or dew.
- Natural oxidation and settling of the coating over time as it adjusts to outdoor conditions.
- Residual manufacturing oils or roll-forming pressure patterns that become more visible as the sheet adjusts to outdoor conditions.
🔍 Is It a Defect?
No. These surface effects are not signs of corrosion or coating failure. They do not affect the structural integrity, protective properties, or expected lifespan of the roofing sheet.
🧼 Can It Be Cleaned?
In most situations, these marks fade naturally over time through regular rain and UV exposure. However, if desired, the surface can be gently cleaned using warm water and a soft cloth. Avoid abrasive materials or harsh chemicals.
2. Polyester Coated Steel Roofing Sheets
Polyester coated steel is a cost-effective option offering reliable performance in mild to moderate environments.
It features a thinner paint coating (typically around 25 microns) and is suited for a wide range of industrial, agricultural, and domestic applications.
Key weathering characteristics:
- UV Resistance: Moderate UV resistance. Colour fading or chalking may become noticeable within 10–15 years, especially on exposed surfaces.
- Durability: While protective, the thinner coating is more prone to cosmetic weathering over time than plastisol.
- Typical Weathering Effects: Colour fade, loss of gloss, and minor surface chalking are normal. These are cosmetic and don’t typically affect the underlying steel.
- Expected Lifespan: 25+ years depending on exposure and maintenance.
Environmental Factors Influencing Weathering
Several external factors affect how your roofing sheets weather over time:
- Location: Coastal, high-UV, or industrial zones accelerate weathering.
- Orientation: South-facing roofs or steep slopes may experience faster UV degradation.
- Maintenance: Periodic cleaning and inspections help prolong appearance and performance.
Minimising the Effects of Natural Weathering
To maximise the longevity and appearance of your roofing sheets:
- Choose the right coating for your location and building use.
- Ensure correct installation practices are followed.
- Conduct regular visual inspections and gentle cleaning.
- Address minor issues early to prevent long-term wear.
If you’re not sure which roofing sheet coating is best for your project, contact us on 01675 462692 for expert advice tailored to your requirements and location.