Preparation and repair: the part that decides whether it lasts
Most coating failures are not coating failures. They are bond failures, and the bond was decided before any colour went down.
Why the surface has to be opened up
A liquid resin bonds to concrete mechanically — it flows into the pore structure and locks in as it cures. A sealed, troweled, or contaminated surface gives it nothing to grip.
Preparation deliberately roughens the concrete to a defined profile. The industry describes this on the Concrete Surface Profile scale, and the profile required rises with the thickness of the system being installed [1].
Two mechanical methods do this work:
- Diamond grinding — planetary grinders with diamond tooling shave off the top layer of cement paste along with old sealers, coatings and surface staining, exposing the pore structure.
- Shotblasting — steel shot is thrown at the slab at speed, fracturing the surface and producing a coarser profile, with shot and debris recovered as it goes.
Acid etching is not equivalent
Acid etching dissolves some surface paste chemically. It produces a shallower profile than mechanical methods [1], does not reliably remove oil contamination or existing curing compounds, and introduces water the slab then has to release.
It is common in consumer kits. For a high-build professional system it is not a substitute for grinding, and a quote that relies on it for one is quoting a different job.
The dust is a genuine hazard
Grinding concrete releases respirable crystalline silica. Federal rules require engineering controls — dust collection with HEPA filtration — rather than leaving it airborne [2] [3].
This matters to you for two reasons. It is a worker-safety obligation, and it is also why a compliant crew keeps the dust out of the rest of your house. A crew grinding dry with no extraction is telling you something about how they work.
Moisture: the failure that shows up months later
Concrete moves water vapour upward from the ground continuously, years after the pour. Put an impermeable film over a slab moving more vapour than the system tolerates, and pressure accumulates underneath until the coating blisters and releases.
This is measured, not estimated by looking. The industry method places probes into holes drilled to a specified fraction of slab depth, seals them, and lets them equilibrate before reading the internal relative humidity. Each coating product publishes its own maximum tolerance, and readings are interpreted against that specific product's limit.
If the reading is too high, a moisture-mitigating primer goes down before the coating. Skipping the test does not make the moisture go away; it just moves the discovery to after you have paid.
A newly poured slab needs to cure before it can be meaningfully tested or coated. Fresh concrete is still releasing water.
Cracks and joints
Control joints are deliberate — saw cuts placed to decide where the slab cracks as it shrinks. Other cracks are not deliberate, and in this region some are associated with ground movement.
The distinction that matters is whether a crack is moving.
Rigid fillers — cementitious patch, standard epoxy — have essentially no elongation. When the slab expands and contracts, a rigid patch fractures and the crack telegraphs through the finished floor.
The standard approach for moving joints uses semi-rigid polyurea fillers, formulated to support the joint edges against wheel traffic while accommodating slab movement [4]. The joint is typically routed out first to give the filler a sound profile to bond to.
What repair cannot do
Filling a crack conceals it and protects it from intrusion. It does not stabilise the slab or stop whatever is moving it. If the concrete keeps moving, a crack can reappear through the coating.
Whether a particular crack can be treated depends on whether it is active, whether the slab is structurally sound, and what is causing it. That requires someone on site. Anyone who tells you every crack can be repaired, sight unseen, is selling rather than assessing.
Contamination
Garages accumulate oil, transmission fluid, and tracked-in road chemicals. Many newer slabs also carry a sprayed curing compound. All of these are bond breakers.
Grinding removes surface contamination. Deep oil saturation may need localised degreasing or a specialised primer beforehand. Contamination that is missed produces a coating that looks fine on day one and releases in patches later.
Ground movement in this region
Pierre Shale is a mapped geologic unit in South Dakota [5], and expansive clays change volume with moisture content, which can move and crack slabs.
Being straight about the limits of that statement: a statewide geologic map does not establish what is under your driveway, and soil shrink-swell potential varies between adjacent parcels [6]. Regional geology explains why this is a common local problem. It does not diagnose your floor.
The sequence
- Assess condition, contamination and existing coatings
- Test moisture; specify mitigation if required
- Mechanically profile the slab
- Rout and fill cracks and joints
- Rebuild spalled and damaged areas
- Re-clean, then coat
Steps 1 through 5 are most of the labour and most of the reason a coating lasts. Anyone quoting a floor without them is quoting a different job.
Sources
Each source below is listed with what it actually supports and what it does not. Manufacturer data describes tested products under stated conditions — not any particular floor.
- Epoxy Floor Coatings: Concrete Surface Profiles Explained — Stronghold Floors
Supports: A description of the Concrete Surface Profile scale and the observation that acid etching produces a shallower profile than mechanical grinding or shotblasting.
Limitations: This is a flooring contractor's own marketing blog. It verifies only what that business advertises and is not independent technical proof; it is not the ICRI standard itself. The underlying ICRI Guideline 310.2 was not directly retrievable for verification.
- OSHA Fact Sheet: Crystalline Silica Exposure — Construction (OSHA 3681) — U.S. Occupational Safety and Health Administration
Supports: Grinding or cutting concrete generates respirable crystalline silica, and federal rules require engineering controls such as dust collection with HEPA filtration.
- Crystalline Silica — Standard 29 CFR 1926.1153 (Construction) — U.S. Occupational Safety and Health Administration
Supports: The federal standard governing respirable crystalline silica exposure in construction, including required control methods for handheld and walk-behind concrete grinders.
- Semi-Rigid Polyurea Joint Filler — Metzger/McGuire
Supports: Semi-rigid polyurea joint fillers are formulated to support joint edges against wheel traffic while accommodating slab movement, which rigid patching materials do not.
Limitations: Manufacturer-published material describing its own product category. Suitability for any specific joint or crack depends on whether the crack is moving or structural, and requires on-site assessment.
- State Geologic Map Compilation — Pierre Shale, South Dakota — U.S. Geological Survey
Supports: Pierre Shale is a mapped geologic unit present in South Dakota, including areas of the western part of the state.
Limitations: A statewide geologic map shows regional unit extent. It does not establish which formation underlies any individual property, nor that a specific parcel is subject to expansive-soil movement. Parcel-level soil behaviour requires a site investigation.
- Web Soil Survey — USDA Natural Resources Conservation Service
Supports: Soil properties, including shrink-swell potential, are mapped at parcel scale and vary between neighbouring sites — so soil behaviour must be checked per address rather than assumed regionally.
Limitations: Soil survey mapping is generalised and is not a substitute for a geotechnical investigation of a specific site.