Floor Coating Surface Is Flat After Application — Why Does It Blister Every Rainy Season?

When the floor has just been completed: the film is intact and flat, adhesion meets requirements, and appearance has no obvious defects. These characteristics only indicate that the construction stage was in good condition — they cannot guarantee that the floor can withstand high-humidity environments long-term. Correct construction does not mean blistering will not occur later.

Concrete substrates have inherent water absorption. If the substrate: has high moisture content, was not fully dry before coating was applied, or is in a persistently humid environment — moisture will continuously migrate upward and exert sustained influence on the coating.

When the rainy season arrives: the groundwater level rises, ambient humidity increases, and substrate moisture vapour pressure increases. When moisture vapour cannot be smoothly released, it may accumulate between the coating and the substrate — gradually forming blistering.

Before application, if: dust is not fully cleaned, oil contamination remains, or the substrate is loose or insufficiently strong — all of these reduce the bonding strength between coating and concrete, making blistering and bubbling more likely during the rainy season.

A floor coating system needs not only wear resistance but also good water and moisture resistance. If the film: has micro-pores or defects, is incompletely cured, or has an insufficiently dense structure — moisture more easily enters the coating interior, accelerating blistering and delamination.

In the early period of floor use: the film remains stable and appearance shows no change. But as the rainy season continues: moisture continuously permeates, substrate moisture acts persistently, and the interfacial bond gradually weakens — problems that were originally hidden gradually become apparent.

In dry weather: the substrate is relatively dry, moisture vapour pressure is low, and the film remains stable. In the rainy season: humidity rises significantly, the substrate continuously absorbs moisture, and moisture vapour continuously migrates upward — blistering is more likely to appear concentrated.