Existing Coatings

If there is something on your slab, your new floor bonds to that thing rather than to concrete, and the whole system is only as strong as the weakest bond in it. The point of this page is to find out what is down there before you commit — including the films you cannot see.

Assume there is something on it

A slab that has never been painted is not necessarily bare. Most concrete is sprayed with a curing compound within hours of being poured, and a great many garage floors have had a clear sealer put on them at some point by a builder or a previous owner. Both are films. Both are invisible on gray concrete. Both will stop an epoxy from bonding.

So the question is not “is my floor painted”. It is “what, if anything, is between my epoxy and my concrete”.

What is probably down there

• Curing compound. Sprayed onto new concrete to hold water in while it cures. Invisible, extremely common, and usually removed by grinding without the owner ever knowing it was there.
• Acrylic or silicate sealer. Clear, sometimes faintly glossy. Water beads on it. Applied by builders, and by owners who wanted a floor that was easier to sweep.
• Garage floor paint. One part, latex or acrylic, usually gray or beige, sold in a can. Wears through in the traffic lanes and peels at the door. The easiest to identify, because it is usually failing.
• One-part “epoxy” floor paint. Sold as epoxy; behaves like paint. Often the coating that lifted under a hot tire and started this project.
• Two-part epoxy. A real coating, frequently with scattered flake in it. Hard, glossy, and firmly stuck wherever it is stuck — which may be most of the floor and not the doorway.
• Polyurethane or polyaspartic. Usually a clear topcoat over something else. Very hard, chemically resistant, and difficult to bond to.
• Tile adhesive and mastic. Old adhesive residue is a coating too, and an awkward one.

Four tests you can do this afternoon

The water drop

Drip water in a dozen places: traffic lanes, the edges, under where the car sits, in the corners. On bare concrete the water darkens the slab and soaks in within seconds. If it beads, sits on top, or takes a minute to go anywhere, there is a sealer or a coating on it — even where you cannot see one.

This is the same test you use at the end of preparation, for the same reason.

The edge and the chip

Look at chips, at joint edges and at the doorway. A coating shows as a distinct layer with a thickness to it, often a different color on its underside. Under the closed garage door, along the wall line and beneath a workbench, you will find it unworn — which is where its original color and sheen are easiest to read, and the best clue to what it is.

The scrape and the tape

Score an X through the coating with a utility knife, hard enough to reach concrete. Press strong tape firmly across the cuts and pull it off fast. Coating that comes away on the tape, or flakes off along the cut lines, is not bonded.

Anything not bonded is coming off. Either you take it off now, or it takes your new floor off with it later.

The solvent rub

Do this with the garage door wide open, nothing burning, no running heater, no pilot light, no smoking, and gloves on. Wet a rag with acetone, hold it against the coating for 30 to 60 seconds in an out-of-the-way spot, then rub.

• It softens, gets sticky, or colors the rag. Single-component — latex, acrylic, a sealer, or one-part epoxy paint. It has to come off.
• Nothing happens at all. Cross-linked — a two-part epoxy, a polyurethane or a polyaspartic. That is a real coating, and it is the harder case rather than the easier one.

This is a field indicator, not an identification. It tells you which family you are dealing with. It does not tell you the product, the year it went down, or whether it is still bonded — the tape test tells you that, and the tape test is the one that decides.

Why an unknown coating is a risk

Coat over an existing film and your floor is not bonded to concrete. It is bonded to that film, which was applied on a date you do not know, over preparation you cannot inspect, by somebody you cannot ask. You are betting the whole job on their work.

Two other things go wrong:

• Chemistry. An old film may not tolerate what goes over it. Coatings can soften, wrinkle or lift when a different chemistry is applied on top.
• Diagnosis. When a floor with an unknown layer underneath it fails, nobody can say whether the material was at fault or the bond beneath it was. That includes us, at the moment you ring and ask for help.

It matters for any claim you might want to make later, too. What we can stand behind is the product installed the way the published method says to install it, and that method calls for bonding to prepared concrete. A floor coated over an unidentified film sits outside it. We would rather tell you that here than after something has gone wrong.

When removal is the only answer

• You do not know what it is, and the tests did not settle it.
• It fails the tape test anywhere. A coating gripping ninety-five percent of the floor and loose in the doorway will fail in the doorway, and it will spread from there.
• It softens under acetone.
• It is peeling, blistering, powdering, or worn through to concrete in the lanes.
• There is more than one layer, or more than one product.
• The slab has a moisture problem. The failing coating is evidence of it, and a second film over the first solves nothing.

ANVIL’s position is straightforward. This system is designed to bond to prepared concrete, and prepared concrete is the surface we know how it behaves on. Take the old coating off. It is a day of unpleasant work, and it removes every unknown in the project at once.

How coatings come off

• Grinding. Diamond tooling with dust extraction. Soft coatings clog ordinary diamond segments; PCD tooling is made for stripping and is what a hire shop will hand you if you tell them what you are removing. Tell them.
• Shot blasting. Fast across open floor and it leaves an excellent profile behind it. Weaker at edges and corners, which still need a hand grinder.
• Chemical stripping. Slow, messy, and it ends with softened coating and rinse water that both have to be disposed of properly. Occasionally the right answer in a space that cannot take dust.

Whatever the method, removal ends where preparation begins, and the target is the same: no film left, no shine anywhere, no gloss hiding in the corners, and water soaking straight in everywhere you drop it. Grinding an old coating makes more dust and worse dust than grinding bare concrete, so the extraction and the respirator matter more here, not less.