Guide
PU floor coating — the epoxy alternative that does not yellow
Epoxy is a hard, durable floor coating with one well-known weakness: sunlight turns it yellow. Polyurethane (PU) is a different family of coating, and the right kind does not yellow. This guide explains the difference in plain language, where it matters, and exactly what the PU top coat Terraesta supplies is — and what it is not.
Epoxy and polyurethane are different materials
Both are two-component coatings: two liquids mixed just before use, which cure into a hard protective film. That is where the similarity ends. Epoxy is valued for its hardness, its bond and its resistance to chemicals, and it is often laid thick, as the floor surface itself. Polyurethane is often used as a thinner top coat, valued for staying more flexible, resisting scratches and abrasion, and — in its UV-stable form — keeping its colour in the sun.
In Indonesia the words get mixed up: "epoxy lantai" is often used for any hard, seamless floor coating. If a quote or a tin says polyurethane or PU, it is not epoxy, whatever the conversation called it.
Why epoxy yellows
Most epoxy floor coatings are built on aromatic chemistry: ring-shaped molecules that absorb ultraviolet light. UV breaks those bonds down, and what they break down into is yellow. The floor does not have to be outdoors. Daylight through a window or a glass door is enough.
The first sign is a yellow or amber cast, most visible on white, grey and other light colours. Outdoors the surface also turns chalky and loses its gloss. It cannot be cleaned off, because it is the coating itself that has changed colour. Additives can slow it down, but standard epoxy is not considered UV-stable.
Why UV-stable polyurethane does not
Polyurethanes come in two kinds. Aromatic PU yellows too. Aliphatic PU is built from molecules that do not absorb UV in the same way, so it keeps its colour and clarity in sunlight. That is why clear coats for exterior use, and the top coats laid over epoxy floors that get daylight, are aliphatic polyurethane. When you compare PU coatings for a sunlit floor, that is the word to look for on the technical data sheet.
Where it matters
- Floors in daylight: living areas with large windows, sliding doors onto a terrace, skylights.
- Outdoors: terraces, balconies, pool surrounds, and covered verandas that still get sun.
- Light and white floors, where yellowing shows first. A dark floor hides it for longer, but the surface still ages.
- Where it matters less: basements, stores and warehouses without daylight, where the hardness of epoxy may be worth more than its colour.
Ultran Super Enamel USE-60
Ultran Super Enamel, USE-60, is the polyurethane top coat Terraesta supplies. Exactly what it is: a two-component, transparent polyurethane coating that acts as a top coat for microcement surfaces. It is suitable for interior and exterior walls and floors, and gives a matte finish that resists wear and weathering. It is polyurethane, not epoxy.
| Type | Two-component polyurethane (PU) |
|---|---|
| Finish | Matte, transparent |
| Use | Top coat for microcement surfaces: interior and exterior, walls and floors |
| Coverage | ≈ 5 m² per unit |
USE-60 is sold as a top coat for microcement surfaces, and that is the only use we describe for it. It is not a replacement for an epoxy floor, and not a floor on its own: it protects the Microcement Extreme beneath it.
Terraesta also supplies Topcoat, a water-based acrylic top coat with a satin finish. Between the two, the difference is the chemistry and the finish: satin or matte.
Where it sits in a microcement floor
- Surface PrimerThe first layer: it stabilises the substrate and evens out absorption.
- FibermeshEmbedded in the base coat; strongly recommended for floors and large areas.
- Microcement ExtremeTwo thin coats by steel trowel or roller, 1–2 mm in total.
- Ultran Super EnamelThe polyurethane top coat that protects the surface.
Going over an old floor? See Replace your floor without demolition.
Choosing epoxy anyway?
If yours is an industrial floor — forklifts, chemicals — epoxy may still be the right answer, and many epoxy floors that get daylight are finished with an aliphatic PU top coat for exactly this reason. That is a job for an epoxy supplier. We do not sell epoxy, and USE-60 is sold as a top coat for microcement, not for epoxy. For the full comparison, see Microcement or epoxy flooring?
