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Keep the two ACI checks separate
ACI SPEC-310.1-20 separates confirmation of placement flatness and levelness requirements from review of measurements taken before polishing. The placement check addresses the slab requirements in the Contract Documents. The pre-polishing check addresses whether the floor is suitable for the specified polished finish.
Flatness can change between those stages, including through curling of slabs on ground. That change matters because flatness at grinding affects the achievable aggregate exposure.
Our new concrete slab specification guide covers how placement, finishing and polishing requirements fit together.
Under ACI SPEC-310.1-20, substrate examination includes:
| Check | What ACI requires |
|---|---|
| Placement and finishing requirements, §3.1.1.1(b) | Confirm that specified surface flatness and levelness requirements when the slab was placed and finished accord with ASTM E1155 and the Contract Documents. |
| Pre-polishing results, §3.1.1.1(f) | Confirm that the Owner’s testing agency results for flatness and levelness measured before polishing are appropriate for the specified polished finish. |
Unless otherwise specified, ACI §1.7.1.2 also assigns the Contractor responsibility for confirming that surface-profile tolerances are adequate to achieve the specified aggregate exposure. These clauses do not supply a flatness value for each exposure level.
The requirements apply when ACI SPEC-310.1-20 is incorporated into the Contract Documents; project-specific requirements govern conflicts. See our ACI specification guide for that relationship.
Measure placement flatness promptly
The Concrete Polishing Association of America (CPAA) recommends measuring floor flatness and levelness within eight hours after final troweling. It calls for an independent testing agency experienced in the procedure and equipped to perform it.
The cited CPAA recommendation names ASTM E1155-96(2008), the method for determining FF floor-flatness and FL floor-levelness numbers.
Use project-specific values
The Solomon Colors Lythic guide specification lists the following values for review at its pre-concrete finishing conference, measured under ASTM E1155:
| Stage | FF: floor flatness | FL: floor levelness |
|---|---|---|
| At concrete placement | 60 | 40 |
| 30 days after placement | 45 | 35 |
Confirm the project’s specified tolerances; these conference-review values are not universal polished-floor requirements.
Coordinate flatness with aggregate exposure
The Concrete Polishing Council (CPC) aggregate-exposure chart identifies flatness at the time of grinding and polishing as an important consideration in selecting the exposure class.
CPC Position Statement #3 recommends coordinating the concrete and polishing subcontracts early so changes in flatness over time, including slab curling, can be discussed and priced before the final polished surface is selected.
Our aggregate exposure and visual acceptance guide covers the finish criteria. Complete the broader substrate acceptance checks before polishing begins.
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Frequently Asked Questions
No. ACI SPEC-310.1-20 treats them separately. One confirmation concerns placement and finishing requirements under ASTM E1155 and the Contract Documents; the other concerns the Owner’s testing agency measurements before polishing and their suitability for the specified finish.
CPAA recommends testing within eight hours, using ASTM E1155-96(2008), by an independent agency experienced in the procedure and equipped for it. That is the timing and edition named in the cited recommendation.
No. The Lythic guide specification lists FF60/FL40 at placement and FF45/FL35 at 30 days for pre-concrete finishing conference review. Those examples do not establish requirements for every polished floor; use the project specification.
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