Epoxy Coatings Outdoors: Can They Be Used?

The short answer: epoxy coatings can be used in some outdoor areas, but not every epoxy system withstands sun, rain, and temperature change over the long term. If the wrong system is used outdoors, the most common result is colour fading, surface chalking, and loss of gloss after a period of sun exposure, even though the coating initially still adheres well.

Why is sunlight the “enemy” of ordinary epoxy?

Ordinary epoxy resin is sensitive to ultraviolet (UV) radiation in sunlight. Under prolonged UV exposure, the surface can yellow, chalk (a fine powder comes off when touched), lose gloss, and fade unevenly, especially in light colours. This is a general property of the material, not an isolated installation fault. In covered areas, shaded balconies, or courtyards with little direct sun, the effect will be far slower than on a yard exposed to sun all day.

Beyond UV, outdoor areas also face rain, standing water, day-night temperature differences, and concrete substrates expanding with heat. Water penetrating through cracks or a damp substrate can cause blistering if the substrate has not been treated for moisture correctly. The question “can it be used outdoors” must therefore always come with the question “how sunny, wet, and damp is that area”.

When is outdoor epoxy still a reasonable choice?

• Areas under a roof or with only intermittent sun, with little direct sun exposure all day.
• Areas needing a seamless, easy-to-clean, load-bearing floor where long-term colour stability is not a strict requirement.
• Outdoor areas with a UV-resistant topcoat over the epoxy system, confirmed by the material manufacturer as suitable for outdoor use.

In these cases, the epoxy acts as the load-bearing, leveling base layer, while sun resistance depends mainly on the topcoat chosen.

When should another system be considered outdoors?

For yards exposed to direct sun all day, uncovered outdoor car parks, or areas requiring long-lasting colour retention, topcoat systems with better UV resistance than ordinary epoxy — for example polyurethane or polyaspartic topcoats, by the general properties of those materials — are often considered. This article only sets out the general direction of choice; the specific topcoat type, thickness, and UV resistance of Kadier products have not been published in an official technical data sheet (TDS), so no Kadier-specific figures are given here. When choosing a material, ask the supplier to confirm in writing that the system is suitable for outdoor use, together with the warranty conditions on colour fading.

Outdoor installation points to note

• Substrate moisture and dew point: applying coatings when the substrate is damp or rain is imminent can easily cause blistering and peeling; measure substrate moisture and check the weather forecast before installation.
• Surface temperature: concrete exposed to sun can be much hotter than the air temperature, affecting working time and curing of the material.
• Drainage: provide falls for drainage and avoid water ponding on the coated surface for long periods.
• Expansion joints: treat the concrete substrate’s expansion joints correctly; do not bridge a joint with a rigid epoxy layer and leave it to crack along the joint.

Conclusion

Epoxy coatings are not “banned” outdoors, but using them outdoors without accounting for UV, rain, and thermal expansion makes long-lasting colour and surface durability hard to achieve. For areas in harsh sun, favour a system with a UV-resistant topcoat confirmed as suitable, or accept that colours will degrade over time and the topcoat will need periodic recoating. For covered areas, epoxy remains a reasonable choice if the substrate is well prepared.

To determine which system suits your outdoor area, refer to the roller-applied RollCoat system for covered areas and the water-based AquaBase system for areas needing low odour and low VOC, then check them against the TDS of the material chosen before finalising the approach.

Illustration: Muharrem Alper on Pexels.

Request a consultation — send a description of the floor area and its intended use to receive advice on a suitable coating system.