Concrete floor coating preparation: a practical checklist
A resin floor is only as reliable as the concrete beneath it. Coating without understanding contamination, moisture, weak material or movement can produce an attractive finish with a short service life. This guide explains the assessment and preparation of concrete before a resin flooring system is installed. Agree the preparation method, profile, primer and acceptance criteria for the complete system and site.
1. Survey the slab before choosing equipment
Walk the whole area, including edges, doorways, drains and locations previously hidden by equipment. Mark cracks, spalls, laitance, dusty patches, oil stains, curing compounds, sealers, old coatings and places where water collects. Identify the floor’s history: previous uses, wash-down, chemical spills, repairs and any evidence of rising moisture. A storeroom, vehicle workshop and commercial kitchen can require different builds.
Check whether the concrete is sound enough to carry the specified finish. A coating cannot restore a delaminating surface or solve a structural defect. Investigate friable areas and refer movement, settlement, structural cracking or persistent water ingress to an appropriate designer. Agree the repair scope before preparation. Photograph defects before the finished floor conceals them.
2. Remove contamination before creating the surface profile
Oil, grease, detergent residue, tyre deposits, paint, adhesives, curing compounds and sealers can interrupt the bond between primer and concrete. Determine the extent of contamination and clean it with a method suited to the material. Oil-soaked workshop bays may need investigation beyond a visible surface stain. A quick solvent wipe or an extra primer coat should not be treated as proof that the concrete is ready.
Clean contaminated zones before final grinding or shot blasting so residue is not spread. Remove incompatible or weak existing coatings. If an old coating appears sound, identify it, check bond and compatibility, and prepare a representative trial. Remove cleaning residues; cleaning alone does not establish the required profile.
ASTM D4258 describes surface cleaning of concrete for coating and explicitly distinguishes cleaning from methods that alter profile. ASTM D4259 addresses abrasion to create profile and remove foreign material and weak laitance. These are related steps with different purposes.
3. Investigate moisture instead of relying on appearance
A surface that looks dry can still contain moisture, and one test location does not describe the whole slab. Review the construction and possible moisture sources, especially where no effective vapour barrier is confirmed, the slab is below grade, water enters at edges, or wet processes operate nearby. Concrete age alone is not an acceptance test.
| Method | Useful result | Limit to remember |
|---|---|---|
| Plastic sheet, ASTM D4263 | Indicates the presence of capillary moisture beneath a sealed sheet. | It does not produce a quantitative moisture value or by itself approve a floor for coating. |
| In-situ relative humidity, ASTM F2170 | Quantifies relative humidity within the concrete at tested locations. | Results describe those locations and the time of testing; they are not a universal product limit. |
| Calcium chloride, ASTM F1869 | Quantifies moisture vapour emission from the surface of a bare concrete floor. | It is not a measurement through an existing coating, leveller or patching compound. |
Agree the method, test locations and acceptance criteria with the project team and coating manufacturer. Record actual results and environmental conditions. If moisture exceeds the agreed condition, identify its source and seek a documented management approach before specifying a primer. A primer described as suitable for damp concrete is not automatically a barrier against rising damp, significant vapour pressure or hydrostatic pressure.
4. Mechanically prepare to the nominated profile
After cleaning, remove laitance, weak concrete and incompatible coatings mechanically. Grinding, shot blasting and other methods produce different textures. Select the method for the concrete and full build. Work edges, coves, thresholds and drains to the same standard as the open floor.
The required concrete surface profile (CSP) depends on the primer, resin layer, thickness and service duty. A thin roller-applied coating and a thicker topping need not have the same profile. ICRI 310.2R provides benchmark profiles for specifying and verifying preparation; confirm the actual target in the approved ALKA system rather than applying one number to every floor.
Use appropriate controls for dust generated by working concrete. In Australia, Safe Work Australia’s crystalline silica guidance describes dust-control approaches for silica-containing materials. After profiling, remove all loose material with suitable extraction, inspect for polishing or missed patches, and prevent trade traffic from recontaminating the surface before priming.
5. Repair defects and preserve movement details
Open and assess cracks rather than filling every line with the same product. Static cracks, voids and local spalls may be repaired with a compatible material after weak edges are removed. Allow the repair to reach the required condition, then re-profile it where needed so the next layer bonds across a consistent surface. Agree the detail at pipe penetrations, plinths, drains, wall junctions and changes in floor level before coating begins.
Moving cracks and movement joints need a detail that accommodates movement. Do not bridge them with a rigid epoxy film. A thin resin layer follows underlying falls and irregularities; it cannot correct drainage or flatness without a designed levelling or screed system.
6. Verify the substrate and approve the system before mixing
Inspect the final prepared surface for soundness, contamination, profile, dust, completed repairs and joint details. Record air and substrate temperatures, humidity, moisture test method and results, and condensation risk. Confirm the primer, any scratch coat, the sequence of layers, the required finish texture and the conditions under which work may start. Where porosity could cause pinholes or outgassing, discuss an appropriate priming approach rather than assuming the body coat will hide the defect.
When concrete strength, old coatings or contamination are uncertain, prepare a representative trial area with the proposed complete build. Agree the inspection method, cure period, test locations and pass criteria before testing. ASTM C1583 can assess near-surface concrete tensile strength; ASTM D7234 covers pull-off testing of a cured coating on concrete. Record the failure mode as well as the measured result, since failure in weak concrete tells a different story from failure at a coating interface.
Minimum pre-coating record
- Floor zones, substrate history, defects, contamination and repair map.
- Specified profile and method used, with inspection of edges and details.
- Moisture method, locations, results and source investigation where needed.
- Completed crack and movement-joint details, with photographs.
- Ambient and substrate conditions, condensation assessment and cleanliness check.
- Approved primer, coating build, current TDS and any agreed trial or adhesion result.
How this connects to an ALKA flooring system
The ALKA-902 Standard Epoxy Floor System is one published example: prepared concrete, an ALKA-100 primer, and ALKA-110 epoxy body and finish coats. It illustrates the need to select the substrate preparation and complete build together; it is not a universal specification for every slab. The ALKA 110 product information calls for contamination removal before final preparation, moisture assessment, repairs, a clean surface and a documented application hold point. It also cautions that ALKA 100 must not automatically be treated as a moisture barrier.
For another duty, moisture condition or finish, compare ALKA flooring systems and request technical project support. Provide the floor area, slab history, site photographs, moisture results, traffic, chemicals, cleaning regime and planned return-to-service date. Request and follow the current approved TDS and written project specification for every selected product before application.
Standards and technical references
- ACI PRC-515.3-20, assessment and surface preparation for protection systems.
- ICRI 310.2R-2013, selecting and specifying concrete surface preparation.
- ASTM D4258-23 and ASTM D4259-24, cleaning and abrasion prior to coating.
- ASTM D4263-24, ASTM F2170-19a and ASTM F1869-23, distinct concrete moisture assessments.
- ASTM C1583/C1583M-20 and ASTM D7234-22, near-surface strength and coating pull-off testing.
- ALKA 110 product page and linked technical documents. Verify the current approved version and project-specific requirements with ALKA.
Need a project-specific build?
Send the substrate condition, exposure, photos and programme to ALKA for a technical review of the complete system.
Planning guidance only. Confirm the current technically approved ALKA TDS/SDS, compatibility, testing and application limits before specifying or installing a system.