Over the past two months, blog updates have been quiet – not because there were no issues on site, but simply because work took priority.
As the Lunar New Year approaches and the pace finally slows, this feels like a good opportunity to reflect on recent site observations and document recurring flooring issues for reference.
This article is based on a recent epoxy coating failure observed at a laboratory in Petaling Jaya. The client’s name is intentionally omitted. The focus here is not the project itself, but the failure mechanism behind it.
The case involves epoxy coating cracking above a floor cable trunking – a detail that may appear minor on drawings, but repeatedly proves to be a predictable point of failure on site.
In practice, most epoxy failures are not random.
They follow patterns.They occur where structure, materials, and movement quietly disagree.
The Context: Epoxy Coating Over Cable Trunking
In this laboratory, the epoxy coating was applied over an existing floor cable trunking route. This condition is a common setup in laboratory flooring, where epoxy coating is applied over cable trunking without dedicated detailing.
Before coating, the cement render floor and the trunking were positioned side by side, separated by a small interface gap. The trunking was fitted with its metal cover, and visually the surface appeared flush and ready for coating.
From an application perspective, the condition looked acceptable. However, from a structural perspective, the epoxy coating was already being asked to bridge across a discontinuity. On one side was the concrete substrate; on the other, a metal trunking system with different stiffness, movement behaviour, and bonding characteristics. This interface, although subtle, is where predictability begins.
Stage 1 - Intact Surface, Hidden Risk
At Stage 1, the epoxy coating appears intact. The surface is smooth, with no visible cracks, delamination, or signs of distress. This stage is often misleading, as the floor gives the impression of stability and completeness.
Mechanically, however, the coating is already spanning across concrete, metal, and the narrow interface between them. No failure is visible yet, but the conditions required for failure are already present beneath the surface.
Stage 2 - Hairline Crack as the First Warning
Over time, a hairline crack begins to form.
This type of epoxy coating cracking is a common early indicator of epoxy coating failure above cable trunking.
What matters is not merely the presence of the crack, but its location. In this case, the crack appears directly above the edge of the cable trunking and follows the trunking route, rather than occurring randomly across the floor.
This is a classic manifestation of stress concentration. Epoxy coating cannot bond equally well across concrete and metal. When movement occurs – whether due to thermal changes, vibration, slab movement, or daily operational loading-stress is repeatedly focused along this narrow interface.
At this stage, the crack may appear minor and is often ignored or simply monitored. In practice, this is the most valuable warning the floor will ever provide.
Stage 3 - Predictable Structural Failure
If the hairline crack is left untreated, the failure progresses. The initial crack widens, secondary cracking develops, and localized breakout of the epoxy coating begins to occur.
In properly detailed floors, what becomes exposed at this stage is the trunking cover rather than the cable itself. By this point, the issue is no longer cosmetic. Moisture ingress becomes possible, deterioration accelerates at the edges, and repairs typically require removal and redesign rather than surface patching.
What began as a fine crack has now fully manifested as a detailing-related structural failure.
Why This Failure Was Predictable
It is tempting to attribute failures like this to epoxy quality, coating thickness, or workmanship alone. In reality, the failure mechanism is structural.
Epoxy coatings perform best when applied over continuous substrates with uniform material properties and properly detailed interfaces. They are far less forgiving when asked to bridge gaps, accommodate differential movement, or act as a transition layer between incompatible materials.
When epoxy is applied directly over cable trunking without proper detailing, failure is not a surprise – it is simply a matter of time.
Closing Thoughts
Most epoxy failures are predictable.
They do not occur suddenly. Instead, they develop quietly and progressively, appearing exactly where the structure dictates.
Understanding where epoxy cracks begin is often more important than knowing how epoxy is applied, because once the crack becomes visible on the surface, the real story has already been written underneath.
P/S: This article is part of a series documenting real-world epoxy coating failure mechanisms observed on site.
