Why Is My Epoxy Floor Chipping?
Troubleshooting
Chipping is a bond problem that has not finished announcing itself yet. A coating that is properly stuck to properly prepared concrete does not chip under normal traffic, it wears. When pieces break away and leave clean grey concrete behind, the coating was never gripping that concrete in the first place. The useful work is figuring out how much of the floor is in the same condition, because chipping at a doorway and chipping across a whole bay are two very different jobs.
General guidance, not a diagnosis of your floor · Authorized dealer for every brand we carry · Counter in Pompano Beach · We speak English, Spanish and Portuguese
What you are looking at
What chipping looks like
Small pieces breaking away rather than large sheets lifting. It concentrates where the floor takes point loads and impact: door thresholds, the lip at a roll-up door, control joints and saw cuts, the edges of the coating where it meets a wall or a drain, and tire paths where a vehicle turns while stationary.
What is underneath the chip tells you most of the story.
Clean grey concrete
The coating released cleanly from the slab. This is adhesion failure, and it means the prep did not give the epoxy anything to hold.
Concrete stuck to the back of the chip
The bond was good. The concrete itself failed. That is a weak or spalling slab, not a coating problem.
A dusty or chalky layer
The coating bonded to laitance, curing compound or an old sealer rather than to sound concrete. It took that layer with it.
If pieces lift in large flexible sheets instead of breaking into chips, that is a different failure. Read why is my epoxy floor peeling instead.
Causes, most common first
Why it happened
1. The slab was never mechanically profiled
Epoxy holds concrete mechanically. It needs a ground profile to key into, and that profile has to be cut with diamonds. Acid etching, pressure washing and a scrubbing machine do not produce one on a hard-troweled slab. A coating applied over a smooth or lightly etched floor is sitting on the surface rather than in it, and it chips at every point where something hits it.
This is the step that decides whether a floor lasts. How to prepare concrete for epoxy covers what a correct profile looks like and how to know you have reached it.
2. Laitance, curing compound or an old sealer left on
New concrete has a weak, fine layer at the surface. Cured concrete often has a membrane-forming curing compound on it. Older floors frequently have a sealer nobody mentioned. All three are loose relative to the slab underneath. The epoxy bonds perfectly to them and they bond poorly to the concrete, so the whole assembly comes off together in chips.
3. Edges and terminations that were never cut in
A coating that simply stops at a wall, a joint or a threshold has an exposed edge, and every exposed edge is a starting point. Traffic catches it, moisture gets under it, and the failure walks inward from there. Saw-cut terminations and properly detailed joints exist for this reason.
4. Film too thin for the traffic
A thin coat has less to give before it reaches the substrate. Rolled out too far to stretch material across a job, an epoxy floor will chip under impact that a correctly built film would shrug off. This is often a coverage misjudgment rather than a technique error, which is why it pays to work out quantities properly with the coverage guide before buying.
5. Too brittle for the job
Hard is not the same as tough. A high-build epoxy with no flexible layer can be brittle under impact, particularly in cold rooms or where heavy items are dropped. Systems for that kind of service use a topcoat with more elongation, or a urethane cement body where thermal movement and impact are constant.
6. Moisture working at the bond from below
Vapor pressure from the slab weakens the bond gradually. It usually shows as blistering or peeling, but on a well-ground floor with good adhesion elsewhere it can show up first as chipping in the wettest areas, near drains, exterior walls and slab edges.
Narrowing it down
How to tell which one you have
| What you see | Most likely cause | Check this |
|---|---|---|
| Clean grey concrete under every chip, floor was acid etched | No mechanical profile | Was the slab ground with diamonds, and to what profile? |
| Chalky dust on the back of the chip | Laitance or curing compound | Slab age and whether a curing compound was used. |
| Concrete stuck to the coating, crater in the slab | Weak concrete | Slab strength and whether the surface is spalling elsewhere. |
| Only at thresholds, joints and coating edges | Terminations not detailed | Were edges saw cut and keyed in? |
| Chips through to concrete, coating feels thin everywhere | Under-applied film | Material used against floor area. |
| Chipping near drains, exterior walls and low spots | Moisture at the bond | Moisture test in those areas specifically. |
One field test settles most of it. Take a sharp scraper to sound-looking coating twelve inches away from a chip. If it pops up with light pressure, the whole floor is in the same condition and you are looking at a full removal. If it will not come up, the problem is localized and repairable.
The repair
Can it be fixed in place?
Localized chipping on a floor that passes the scrape test
Yes. Grind back to firmly bonded coating, feather the edges so the repair does not read as a step, rebuild the layers in that area and then topcoat the whole floor so the color and gloss match. Do not just dab material into the chip: the patch will stand proud and chip again at its own new edge.
Chipping along joints and thresholds
Repair the detail rather than just the surface. Saw cut a clean termination, fill the joint with the right material, and rebuild the coating into it. A joint that was ignored the first time will fail again exactly the same way.
Widespread chipping, or coating that lifts on the scrape test
Grind it off. We say this knowing it costs more than a patch, because a patch over a floor with no mechanical bond fails again on the same schedule. Chipping is usually the visible corner of a bond problem that covers the whole slab.
The removal is also the opportunity: the floor gets the diamond profile it should have had, the moisture gets tested, and the rebuild actually lasts. How to choose a concrete floor grinder covers machine sizing, and rent versus buy covers the economics.
Next time
The prep that prevents it
Grind to a real profile
Diamonds, not acid. Take it until you are into sound concrete across the entire floor, edges included, and the profile is consistent. Edges and corners need a hand grinder and they are where most floors are under-prepped.
Prime the ground slab
A primer wets into the open profile and gives the build coat a chemically bonded layer to grip rather than raw porous concrete.
Detail every termination
Saw cut where the coating stops. Key it into joints. Never leave a feathered edge sitting on the surface where traffic can catch it.
Build the film the system calls for
Stretching material thin to cover more area is a false economy that shows up as chipping within the first year. Work the quantity out properly with the coverage guide.
Match the system to the abuse
Forklift traffic, dropped tooling, thermal shock and washdown all call for different builds. A flake or quartz broadcast adds impact resistance and thickness, and a tougher wear coat takes the hits. Tell us what happens on the floor and we will spec it layer by layer.
Related symptoms
Often confused with
Talk to somebody who has stood on a slab
Tell us what you are seeing
This page is general guidance. Chipping has several possible causes and a web page cannot see your concrete. Tell us what is on the back of the chips, how the slab was prepared and whether sound coating lifts under a scraper, and we can usually tell you quickly whether this is a patch or a removal.
Latux Epoxy
2201 N Andrews Ave, Suite 108
Pompano Beach, FL 33069
(800) 413-1427
Monday to Friday, 8:00 AM to 5:00 PM.
Saturday by appointment.
Sunday closed.