Floor coating thickness is measured in mils — thousandths of an inch. It sounds like a lot of precision for a floor, but the difference between 5 mils and 20 mils is the difference between a thin paint film and a durable coating system. Understanding why thickness matters — and what determines how thick your coating actually ends up — helps you evaluate contractor claims and product specifications more accurately.
What Is a Mil?
One mil = 1/1000 of an inch = 0.001 inches = about 25.4 microns. For reference: a human hair is approximately 2.5–3.5 mils thick. A standard sheet of copy paper is about 3–4 mils. A typical paint coat on a wall is 1–2 mils dry. A professional floor epoxy base coat applies at 15–20 wet mils and cures to a dry film of similar thickness (because 100% solids epoxy has no solvent to evaporate).
Wet Mils vs Dry Mils: The Solids Content Trap
This is where most consumer confusion lives. "Wet mils" describes the thickness of the coating when it's applied — while it's still liquid. "Dry mils" describes the thickness after all solvents or carriers have evaporated and only the solid polymer remains. For most paints, these are very different numbers.
A 40% solids water-based "epoxy paint" applied at 20 wet mils cures to only 8 dry mils — because 60% of the wet volume evaporates as water. A 100% solids epoxy applied at 20 wet mils cures to approximately 20 dry mils — because there's nothing to evaporate. The entire wet film becomes dry film.
This is why solids content matters more than wet mil claims. A contractor who says "we apply 20 mils of epoxy" needs to specify whether that's wet or dry, and what the solids content is. Otherwise the number is meaningless.
Our System's Actual Thickness
Total dry film thickness of our full system: approximately 25–30 mils above the concrete surface. With the chip broadcast layer accounted for, effective coating depth over the concrete ranges from 30–40 mils including the encapsulated chip material.
Thickness by Application Type
| Application | Minimum DFT | Our System DFT | Why It Matters |
|---|---|---|---|
| Residential garage (foot traffic only) | 10–15 mils | 25–30 mils | More film = longer wear life before thinning through |
| Residential garage (vehicle parking) | 15–20 mils | 25–30 mils | Vehicle point loads require sufficient film build |
| Commercial / light industrial | 20–30 mils | 30–40+ mils (multi-coat) | Forklift traffic, pallet jacks, continuous use |
| Pool deck / outdoor | 15 mils | 20–25 mils (no chip) | Thinner film OK outdoors — drainage slope preserved |
Does Thicker Always Mean Better?
Up to a point, yes — more dry film thickness means a longer wear life, because it takes longer to abrade through a thicker film to the point where the concrete substrate is exposed. But beyond a certain threshold (roughly 30–40 mils for residential use), additional thickness provides diminishing returns and can introduce its own problems: very thick single coats can crack through thermal expansion, and excessive self-leveling epoxy can trap solvents and develop surface defects.
The right specification is adequate dry film thickness from a 100% solids product applied at correct coverage rates — not the thickest possible coating regardless of chemistry. A 25-mil system of 100% solids epoxy + polyaspartic topcoat outperforms a 40-mil system of 40% solids water-based product in every meaningful performance metric.
How to Verify What You're Getting
Ask any contractor for the Technical Data Sheet (TDS) for the products they're using. The TDS will specify: solids content by volume, recommended wet film thickness, theoretical dry film thickness at that spread rate, and coverage per gallon. These are the numbers that tell you what you're actually getting — not the marketing claims.
We use 100% solids epoxy base coat and aliphatic polyaspartic topcoat on all residential garage floors. We can provide TDS sheets for both products on request. The math is straightforward and the numbers hold up.
A System That Delivers What It Claims
We're happy to explain exactly what products we use, what the dry film thickness is, and why we spec what we spec. No vague marketing — just an honest system that works. Katy TX and Greater Houston.
(832) 698-9040 — Call or Text