Most failed roofs in hot, wet climates were not failed products. They were the right product on the wrong roof. Before comparing prices, answer three questions about the structure itself.
Does the deck move?
- A concrete slab on a long span, a metal deck, or anything above a car park moves enough to split a rigid coating within two seasons.
- Movement means elastomeric: acrylic for light movement, polyurethane where the deck genuinely works.
- A stable ground-bearing slab does not need elongation, and paying for it is waste.
Is it exposed to sun, or buried?
- Exposed roofs need UV stability and a reflective surface — an unprotected bitumen or polyurethane film chalks and embrittles fast under equatorial sun.
- Buried or tiled-over systems can use cementitious membranes that would never survive exposure.
- Reflectance is worth real money to the building owner: a white acrylic roof runs far cooler than a black one, and the air-conditioning bill shows it.
Who is going to apply it?
- Torch-applied membrane needs trained crews and a site where open flame is allowed. Many are neither.
- Liquid systems are forgiving of skill but unforgiving of thickness — specify wet film gauges or you will get half the coverage you paid for.
- If the answer is 'the building owner's nephew with a roller', that decides the system regardless of what the spec says.
The short version
Match elongation to movement, UV resistance to exposure, and application method to the crew you actually have. Get those three right and almost any reputable formulation works.