Seamless Resin and Microcement Flooring

Resin and microcement are sold as finishes and treated as such: this is the misunderstanding behind nearly every dispute in this trade. In fact they are thin coatings rigidly bonded to the substrate, without the thickness or the joints that let a porcelain tile absorb movement. What shows on the surface is almost always a defect of the screed, not of the product. Two checks follow from this, and they decide the outcome; both belong before the material is ordered. The first is the screed's residual moisture, measured with an instrument and not with a hand: a screed still damp keeps releasing vapour upwards, and under an impermeable coating that vapour accumulates until it lifts the resin in blisters. The second is reading the joints: every structural joint and every movement joint in the screed must be carried through to the surface, because if the seamless floor bridges them, the crack will be what reminds you where they were. Resin and microcement are not the same thing, and the choice is not an aesthetic one. Resin is an impermeable polymer film: it seals the floor, resists chemicals and cleans well, but it lets nothing out and therefore demands a dry substrate and a vapour barrier under the screed. Microcement is a modified cementitious mortar: it stays mineral and tolerates a less than perfectly dry base, but it needs a protective finish because on its own it takes up stains. The last point is that these floors are not laid: they are applied, by hand, in thin superimposed coats. Success depends on the continuity of the gesture and on ambient conditions during application and curing — temperature, relative humidity, absence of draughts. A door left open on a windy day is enough to mark a whole room for good.

In the showroom they are chosen by colour, which is why half the trouble starts before the site does. The real difference is how they behave with water. Resin is a continuous, impermeable polymer film: excellent where hygiene and chemical resistance are needed, but over a base still releasing vapour it becomes a trapping membrane and blisters off. Microcement is a modified cementitious mortar: it stays mineral and lets a little through, so it lives with less than perfect bases and with lime substrates, but on its own it stains and must be protected. In practice: if the screed is new and properly dry, or the room is chemically aggressive, resin does its job. If you are working on an existing floor, in a historic building or on a base whose full history is unknown, microcement forgives more.

The blister is the commonest pathology and the most misread. It does not come from above, it comes from below. A screed still holding water keeps releasing it as vapour; while the floor is open that vapour leaves and nobody notices, but as soon as an impermeable film is laid over it the vapour meets a ceiling. It gathers at the interface, pressure builds slowly and at some point it beats adhesion: the coating lifts in a round dome, often months later and almost always after the room has been heated for the first time, because warmth speeds up migration. That is why the complaint always arrives in autumn. There is no cure after the fact: you cut, dry and redo the area, hoping the moisture has dropped meanwhile. The only real defence is the measurement taken beforehand.