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Floor & Deck Coatings · From the field
Why garage floor coatings peel — and the four questions that predict it
A coating that lifts in sheets, bubbles in the middle of the bay, or comes up with the tyres on a hot August afternoon has almost always failed at the concrete, not in the product. What actually goes wrong, and what a quote has to tell you before you sign it.
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Quick answer
Why do garage floor coatings peel?
Because the bond to the concrete failed, and in the great majority of cases that traces back to preparation rather than to the coating. The four usual causes are a slab that was never mechanically profiled so the coating had nothing to key into, moisture coming up through the slab from below and pushing the coating off, a slab that was still too young or too damp to coat, and contamination — oil, sealer, or old coating residue — left in the concrete. A coating is only ever as good as the surface under it, which is why the preparation is most of the cost and all of the risk.
The coating is the cheap part
When people compare garage floor quotes, they compare products — epoxy against polyaspartic, this many coats, this flake blend. Those differences are real and worth understanding, but they are not usually what separates a floor that lasts from one that fails. What separates them is what happened to the concrete before anything was poured onto it, and that is the part of the job a homeowner cannot see on a finished floor and cannot easily compare between quotes.
Think of it the way a painter thinks about a wall. The paint on a properly prepared wall and the paint on a dusty, glossy, slightly damp wall is the same paint. One lasts fifteen years and one peels in two. Nobody blames the tin. With garage floors the equivalent mistakes are easier to make, harder to see, and considerably more expensive to undo, because removing a failed coating from concrete is worse work than applying one.
So the useful way to read a coating quote is to read the preparation. If a quote for a two-car garage is notably cheaper than the others and does not mention grinding, moisture testing or crack repair, the saving is coming from somewhere, and that somewhere is the part that determines whether the floor is still there in five years.
Mechanical profile: the one thing that cannot be skipped
A troweled concrete slab has a hard, closed surface. Coatings do not stick to it chemically in any meaningful way — they key into it mechanically, which means the surface has to be opened up so there is texture for the coating to grip. That is done by diamond grinding or shot blasting, and the result is a uniformly abraded, matte, slightly rough surface with the laitance and any sealer removed.
The shortcut is acid etching. It is quicker, cheaper and requires no equipment, and on some slabs it produces something that looks a bit like a profile. It does not reliably produce one. It will not remove a sealer, it does not touch oil contamination, it is wildly inconsistent across a slab that has different densities in different areas, and it leaves residue that has to be fully neutralised and rinsed or it interferes with the coating. Most of the peeling garage floors we are asked to look at were etched rather than ground.
The test for it is easy and you can do it yourself before anyone starts: drop water on the bare slab. On a properly profiled floor it darkens and soaks in within seconds. If it beads and sits, the slab is sealed or closed and nothing is going to bond to it until that is mechanically removed. A contractor who is happy for you to do that test is a contractor who has planned to grind.
Moisture from below, which is a Maryland problem specifically
A concrete slab on grade is a wick. Unless there is an intact vapour barrier under it — and in houses built before that was standard practice there often is not — ground moisture moves up through the slab continuously, evaporating off the surface where you never notice it. Put an impermeable coating on top and the moisture has nowhere to go. It collects at the bond line and pushes, and eventually the coating lifts in blisters or sheets with the back of each piece slightly damp.
This is common in Frederick County and across Central Maryland because of how much of the housing stock predates modern under-slab detailing, and because of how wet the ground gets here in spring. It is also completely testable. A calcium chloride test or a relative-humidity probe gives a number before anybody commits to a product, and if the number is high there are moisture-tolerant primers and vapour-barrier systems designed for exactly that situation. What there is not, is a way to get a standard coating to stick to a slab that is actively driving moisture upwards.
The reason this gets skipped is that the test takes time — days, for the accurate versions — and costs a little, and on most slabs it comes back fine. But the slabs where it does not come back fine are precisely the ones where a coating will fail, and nothing about the look of a dry garage floor on a July afternoon tells you which you have. If a quote does not mention moisture at all, ask.
Hot-tyre pickup, and why polyaspartic gets recommended
Hot-tyre pickup is the failure where a car is parked after a drive and the coating comes away stuck to the tyre, leaving a bare patch the shape of the contact area. It happens because a warm tyre is both hot and slightly tacky, and it bonds to a coating that has not fully cured or that softens with temperature. Where the coating-to-concrete bond is weaker than the tyre-to-coating bond for those few minutes, the coating loses.
Two things make it much less likely. The first, again, is a real mechanical profile, because a well-keyed coating is not going anywhere regardless of what a tyre does. The second is the chemistry: polyaspartic and polyurea topcoats are considerably more resistant to this than a standard epoxy, cure far faster, hold colour better in UV, and stay more flexible across a temperature range. That is why they have largely taken over the top layer of residential garage systems, usually over an epoxy or moisture-tolerant primer rather than instead of one.
They cost more and they are less forgiving to apply, because the working time is short and there is no going back to fix a run after the fact. That is a reasonable trade. What is not reasonable is treating polyaspartic as a substitute for preparation. A polyaspartic floor on an unground slab fails in exactly the same way as an epoxy one, just more expensively.
What to ask before you sign anything
Four questions, and the answers tell you nearly everything. How will the slab be profiled, and with what equipment? Will moisture be tested, and what happens to the specification if the reading is high? How will the existing cracks and any pitting or spalling be dealt with before coating? And what is the cure schedule — specifically, when can the floor be walked on and when can a vehicle be parked on it?
That last one is worth pressing on, because it is the commonest source of a coating failing in its first week. A floor that gets a car on it before the system has cured is a floor with a tyre print in it. Polyaspartic systems are genuinely fast — often back in service the next day — and epoxy systems are genuinely not, and a contractor who gives you a vague answer about cure time has either not thought about it or does not want to tell you that you cannot use your garage until the weekend.
Cracks matter as well. A coating is a thin film and it will not bridge a moving crack; it will simply crack in the same place, usually within the first season. Static cracks get cut out and filled with a rigid repair material that is then ground flush, which is work and shows up in the price. A quote that coats straight over existing cracks is quoting for something that will reproduce them.
None of this makes a coated garage floor a risky purchase. Done properly it is one of the better-value things you can do to a house — it is hard-wearing, trivial to clean, and it transforms how a garage feels. It just has to be bought on the preparation rather than on the brochure.
If you only skim
The short version
- Coating failures are preparation failures far more often than product failures. Read the quote for grinding, moisture and crack repair, not for the brand.
- Acid etching is not a substitute for diamond grinding or shot blasting. Most peeling floors we see were etched.
- Test it yourself: water dropped on a bare slab should darken and soak in within seconds. If it beads, nothing will bond.
- Older Maryland slabs often have no vapour barrier. Moisture driven up from below pushes coatings off, and it is testable before you commit.
- Polyaspartic resists hot-tyre pickup and UV far better than epoxy, and cures faster. It is not a substitute for a proper profile.
- Ask when a car can go back on it. A premature vehicle is the commonest first-week failure.
The trade behind this post
Floor, Deck & Balcony Coatings
Reading because you have this exact problem? Call and describe it. You’ll get a straight answer on whether it’s something we do and roughly what it runs.
(301) 524-1729See how we do floor & deck coatingsWhat floor & deck coatings costs in MarylandOn the job
The work this post is about.
Trade photography, stage by stage. Photos of our own recent jobs come out at the walkthrough, on the actual house.
Straight answers
What homeowners ask next
Not covered here? Call and ask — you’ll get a real answer, not a “depends on the job”.
For a two-car garage, a properly prepared full flake system with a polyaspartic topcoat typically lands in the low-to-mid four figures, with the spread driven almost entirely by the slab rather than the finish. A sound, clean, crack-free slab is at the bottom of the range. One that needs extensive crack repair, spall patching or a moisture-mitigating primer is at the top. Our cost guide breaks the figures down by square footage and by what each layer of preparation actually adds.
Not over the failed coating, no. Whatever is lifting has to come off completely, because a new coating bonded to a failing one inherits its failure. Removing an old coating is grinding work and it is the least pleasant part of this trade, so it is a real cost and we will price it visibly rather than hiding it. The one piece of good news is that the removal usually tells us exactly why the first one failed, which means the second one can be specified properly.
It depends entirely on what you expect from it. The products in those kits are not the problem; the preparation they instruct is. They almost universally specify acid etching rather than grinding, and they contain no provision for moisture testing. On a young, clean, dry, unsealed slab a kit can give a few decent years. On an older slab, a sealed one, or one with moisture coming through, it will fail, and you will have added a removal job to the eventual proper one.
A properly prepared polyaspartic system on a sound slab should be giving good service well past ten years, with the wear showing as gradual dulling in the traffic paths rather than as failure. The variable is not really time, it is whether the bond was right on day one. Coatings that are going to fail generally do it in the first two years, which is a useful thing to know — if a floor is still perfect after two winters, it is very likely to keep going.
Across Frederick County and Maryland within about 90 minutes of Frederick — eight counties from Hagerstown across to Annapolis. Maryland only; we do not work in Washington, DC. Call (301) 524-1729, or send photos of the slab, any cracks and any existing coating through the quote form and we will tell you what the preparation is likely to involve.
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