Which coating should you choose for a metal roof? Polyester vs. polyurethane (PUR). And where to start.
Author: Affari OÜ
23.09.2025
Polyester and polyurethane (PUR) are two of the most common coatings for metal roofs. Both have their own strengths. Below are the key differences to help you make the right choice based on your budget, climate and usage demands.
Polyester coating: affordable and practical
- Cost: Generally lower – an affordable solution.
- Protection: Good resistance to UV radiation and mechanical impacts, but overall less resistant to UV degradation than PUR.
- Elasticity: Medium – suitable for regions with moderate temperature fluctuations.
- Appearance: The colour and appearance are retained well; wide range of colours.
- Durability: Average – typically 5–10 years, depending on operating conditions.
Polyurethane coating (PUR): superior protection and a long lifespan
- Cost: Generally more expensive than polyester.
- Protection: Very good resistance to UV, mechanical damage, chemical exposure and weather conditions.
- Elasticity: Very high – withstands the expansion and contraction of metal caused by temperature changes.
- Appearance: Smooth, glossy surface and deep, intense shades.
- Durability: 10–15 years or more, provided the base sheet, pretreatment and application are done correctly.
In brief
PUR coating offers greater protection, stability, and durability, while polyester is a more budget-conscious option, which performs well in moderate conditions.
Where is it not recommended to install a matte coating?
1) Seaside and coastal areas
- Reason: Salty air accelerates corrosion, especially if the coating sustains mechanical damage.
- Concern: A matte surface generally has a more “open” microtexture and withstands salt spray less effectively than glossy PVDF.
- Better choice: Aluzinc base sheet + glossy PVDF coating or a different roofing material.
2) High humidity and biological damage
- Reason: The matte surface gets dirty more easily, and moisture remains longer; lichen, moss, and mold may develop.
- Typical locations: Shaded areas, plots with dense vegetation, forest edges – the roof does not dry quickly.
3) Polluted industrial areas
- Cause: Acids, chemical compounds, soot and dust damage the matte coating, which self-cleans less effectively.
- Result: Faster color fading, chalking, and corrosion.
4) Large day-night temperature fluctuations
- Cause: Frequent fluctuations (hot during the day, cold at night) promote the formation of microcracks.
- Particularly risky: Areas where daytime temperatures are ~+30 °C and night frost occurs at night – water can seep under the coating, freeze, and damage the surface.
5) Roofs with a slight pitch (less than ~8°)
- Reason: Water does not drain away quickly enough; the matte surface has mediocre self-cleaning properties.
- Result: Standing water and dirt accelerate the aging of the coating.
Avoid the following during use
- Non-abrasive maintenance: Do not use harsh cleaning products – the matte surface scratches easily.
- Wear appropriate footwear: Soft-soled shoes only; otherwise, micro-marks and damage will occur.
- Regular inspection: Clean drains, joints, and dirt deposits – this extends the lifespan of both the coating and the sheet metal.
What metal thickness should you choose?
Sheet metal thickness affects structural rigidity, resistance to mechanical impacts (hail, roof maintenance), coating lifespan and aesthetics (less “waviness”, vibration, and noise).
Recommended thicknesses by building type
| Building type | Recommended thickness | Comment |
|---|---|---|
| Residential building | 0,50–0,55 mm | The best balance of price, strength and appearance. |
| High-quality detached house/apartment building | 0,55–0,60 mm | Greater rigidity, better dimensional stability, less noise. |
| Auxiliary buildings (sheds, etc.) | 0,45–0,50 mm | Potential savings; for residential buildings, preferably no less than 0,50 mm. |
| Industrial/commercial buildings | ≥ 0,60 mm | Required for large spans and heavy snow loads. |
Important considerations when choosing thickness
- Minimum for a residential building – 0,50 mm.
Thinner sheet metal deforms more easily, does not hold fasteners well, and is noisier in the rain.
- Ask for “sheet metal thickness BEFORE painting”.
Manufacturers often specify “0,50 mm”, but this may include the zinc and paint coating layers. Specify: “steel thickness before coating”.
- Complex roofs and snow loads = do not cut corners.
More joints, bends, and penetrations mean greater rigidity requirements.
- Standing seam or classic profile (not trapezoidal profile/tile-effect profile).
Recommended from 0,55 mm, especially for double standing seam applications.
Summary and logical conclusion
- A limited budget and a moderate climate? Choose polyester – good value for money and adequate protection.
- Maximum reliability, intense UV exposure, and a harsh environment? Choose PUR – better flexibility, chemical and mechanical resistance, and a longer service life.
- A matte surface is not always the best choice. Coastal, humid and polluted areas or a low slope require PVDF glosssolutions or another material.
- Sheet metal thickness matters. For residential buildings, from 0,50 mm, and in more demanding conditions, 0,55–0,60 mm or more.
If you base your choice on location, climate, intensity of use, and budget, you will get a roof that retains its color, shape, and watertightness for years. Even the best coating requires the right underlay, proper pretreatment, installation, and maintenance – this is how the metrics work in real life, not just in the catalog.