Polyurethane (PU) systems like Polyroof Protec, Kemperol 2K-PUR and Bauder LiquiPUR have a strong foothold in commercial flat roofing. Silicone is a different chemistry doing the same job. Both are legitimate choices for roofs across Ireland and Northern Ireland. Here’s an honest, specifier-grade comparison to help you choose the right one for your project.
How PU works
PU liquid membranes are typically three-layer, polyester-reinforced systems: base coat, reinforcement fleece, topcoat. They cure by chemical reaction (often two-component) to form a tough, chemically-resistant elastomer. Polyroof Protec is one of the best-known PU systems; Kemperol and Bauder LiquiPUR serve similar markets.
PU systems excel on complex details — balconies, upstands, pipe penetrations, waterproof floors — where the reinforcing fleece adds puncture resistance. They are also the chemistry of choice for green roofs and inverted roofs where additional loading is expected.
How silicone works
Silicone is a single-component, moisture-cured elastomer applied in one or two coats. It’s a high-solids liquid that self-levels and cures to a seamless hydrophobic membrane. It’s not typically reinforced with fleece (though fibre-reinforced detail products like GacoFlex SF42 are available for seams and laps).
Where silicone wins
- Large-area flat and profiled roofs. Silicone’s single-coat, high-solids application is dramatically faster on big warehouses, factories and industrial sheds.
- Ponding water. Silicone is explicitly ponding-rated. PU systems can tolerate ponding but are not as naturally suited.
- UV stability. Silicone is more UV-stable than PU over very long periods.
- Cool roof performance. White silicones reflect more solar radiation than typical PU topcoats.
- Cost per m² on large roofs. Silicone’s single-coat build is typically 20–30% cheaper per m² installed on 1,000+ m² roofs.
- Recoatability. Silicone recoats silicone with no strip required. PU systems typically need full strip-and-replace at end of life.
Where PU wins
- Complex detailing. Walk-on balconies, terraces, upstands, planters — the reinforcement layer makes PU the stronger choice.
- Chemical exposure. PU is more resistant to oil, fuel and chemical spill than silicone.
- Mechanical loading. Green roofs, inverted roofs, paved walkways — PU carries load better.
- Fast cure. Some 2K PU systems cure in under 2 hours — useful on weather-sensitive programmes.
- Decorative finish. PU topcoats are available in a wider colour and aggregate range.
Side-by-side table
| Metric | GacoFlex S42 (silicone) | Polyroof Protec (PU) |
|---|---|---|
| Chemistry | Single-component silicone | 2K PU + polyester fleece |
| Coats / layers | 1 (topcoat only) | 3 (base + fleece + top) |
| Ponding rated | Yes | Tolerant, not rated |
| Typical warranty | Up to 20 yrs | Up to 20 yrs |
| UV stability | Excellent | Good (pigmented) |
| Fire Class A | Yes (UL Listed) | See manufacturer’s fire data |
| Best use | Large-area flat/profiled roofs | Balconies, terraces, detail-heavy refurbs |
| Relative installed cost | Lower on large areas (single coat) | Higher (three-layer build) |
Honest advice
If your project is a 3,000 m² warehouse roof with some ponding, silicone is the more efficient answer. If your project is a 200 m² balcony terrace with heavy foot traffic and tile upstands, PU is the more durable answer. We supply silicone because we believe it’s the right fit for the majority of commercial flat-roof refurbishments — but Polyroof, Kemperol and Bauder are all excellent companies building excellent products for their markets. There’s no winner here, only the right chemistry for the job.
See our full silicone guide or email info@duratite.ie for honest advice on your specific project.