Polyaspartic topcoat
A quarter of a millimetre, and everything that ever touches the floor touches this
Nothing you do to the floor reaches the base coat. Tyres, trolleys, dropped spanners, mop chemicals and sunlight all land on the topcoat, which goes on as two coats of 125 microns and is the layer that will eventually need renewing.
Polyaspartic is an aliphatic polyurea. The word that matters is aliphatic: its molecular backbone does not break down under ultraviolet light, which is why it holds colour where an epoxy topcoat goes amber.
The recoat window is the reason we use it
It is touch-dry and ready for its second coat in about an hour, against overnight for epoxy. On an occupied site that is the difference between a floor laid over a weekend and a unit shut for most of a week, and it is usually what decides the system rather than any property of the cured film.
The same speed is the problem with it. There is no leisurely correction: it is rolled in one continuous wet edge, and stopping in the middle of a bay leaves a line that is there permanently.
Gloss is a choice, not a grade
The same product is available anywhere from a near-mirror to a flat matt, and a lower gloss is not a lower quality. What it changes is maintenance: high gloss shows every scuff and every footprint, matt hides them and shows dust instead.
For a domestic garage we usually argue for satin. A showroom wants the gloss and accepts the cleaning that comes with it. What gloss does not do is make a floor less slippery; that is the aggregate in group II, not the sheen.
It is the layer designed to be replaced
After eight or ten hard years the topcoat will be worn through in the traffic lanes while the base coat under it is untouched. That is the system working. A light abrade and a fresh topcoat gives the floor back for a fraction of what it cost, and without taking the slab back to bare concrete.
How to tellCompare a strip of floor that gets daylight with one that lives under a bench. On a polyaspartic finish they are the same colour after five years. Epoxy left as its own topcoat goes visibly amber wherever the light reaches it, and the line between the two is the shape of the window.
What to ask
Ask whether the topcoat is aliphatic. If the answer is vague, or if the quote lists "epoxy" for both the body and the finish, you are being offered a floor that will change colour in daylight, and you will notice it first along whichever wall has the windows.