As architects and specifiers, defining and verifying floor flatness (FF) and levelness (FL) is crucial for ensuring design integrity, proper performance of finishes, operational functionality, and mitigating liability. This guide provides a technical overview of relevant standards, specification requirements, and critical integration points throughout the project lifecycle.

Specification Summary

• Core Standard: ASTM E1155 defines the methodology for determining FF and FL numbers.
• Tolerances: ACI 117 provides standard tolerance classifications for concrete construction.
• Coordination: Requires integration with Division 01 (Quality Requirements), Division 03 (Concrete), and Division 09 (Finishes).
• Documentation: Rigorous documentation throughout all project phases is essential for quality assurance and risk management.

1.0 Technical Overview & Standard References

Understanding the applicable standards is fundamental to proper specification.

1.1 Key Standard References

• ASTM E1155: Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers. This is the primary standard for measuring and calculating F-numbers on concrete slabs.
• ACI 117: Specification for Tolerances for Concrete Construction and Materials. Provides standard FF/FL tolerance classifications (e.g., Conventional, Flat, Very Flat) and minimum local values (MLV).
• ACI 302.1R: Guide for Concrete Floor and Slab Construction. Offers guidance on designing and constructing quality concrete floors, including factors affecting flatness/levelness.
• ASTM F710: Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring. Addresses substrate conditions prior to resilient flooring installation, including requirements for smoothness (e.g., max variation over 10 ft), but is distinct from the overall FF/FL measurement defined by ASTM E1155.
• Division 01: Quality Requirements (Testing agency qualifications, reporting).
• Division 03: Cast-in-Place Concrete (FF/FL requirements, testing timing).
• Division 09: Finishes (Manufacturer requirements for substrate flatness).

1.2 Critical Parameters & Distinctions

It’s vital to specify the correct parameters based on the intended outcome:

Note: Project specifications must define the required FF/FL numbers (e.g., FF 35 / FL 25) based on ACI 117 classifications or specific project needs.

2.0 Specification Guidelines & Documentation

Clear documentation requirements are essential at each phase.

2.1 Pre-Construction Documentation

• Specifications (Div 01, 03, 09): Clearly define required FF/FL numbers (Overall and Minimum Local Values per ACI 117), reference ASTM E1155 testing method, specify testing timing, testing agency qualifications, reporting requirements, and remediation procedures for non-conformance.
• Drawings: Indicate areas requiring different or more stringent FF/FL tolerances (e.g., labs, equipment pads, areas with sensitive finishes).

2.2 Construction Phase Documentation

• Submittals: Testing agency qualifications, equipment calibration records, proposed measurement plan/layout.
• Test Reports: Timely submission of detailed ASTM E1155 reports after each test section is measured.
• Corrective Action Records: Documentation of any non-conforming areas, proposed remediation methods, approvals, and verification re-testing results.

2.3 Post-Construction Documentation

• Final Test Reports: Compiled reports verifying compliance for all tested areas.
• As-Built Records: Incorporation of final floor elevation data or compliance statements into project closeout documents.
• Warranty Documentation: Linking flooring warranties to verified substrate compliance.

3.0 Critical Phase Integration

Integrate FF/FL considerations throughout the project timeline.

3.1 Design Development (DD)

• Establish performance requirements based on intended use, finishes, and equipment.
• Identify critical areas needing higher FF/FL values. Consult ACI 117 classifications.
• Outline testing strategy and general requirements.

3.2 Construction Documents (CDs)

• Section 01 40 00 – Quality Requirements: Specify testing agency qualifications, submittal requirements (reports, calibration), and non-conformance procedures.
• Section 03 30 00 – Cast-in-Place Concrete: Define specific FF/FL Overall and Minimum Local Values required for different areas, reference ASTM E1155, specify testing timing (within 72 hours), and detail requirements for corrective action. (See template below).
• Section 09 XX XX – Specific Flooring Sections: Reference required substrate tolerances from Section 03 30 00 and include flooring manufacturer’s specific flatness/smoothness requirements (which may necessitate additional surface prep checks beyond FF/FL).

3.3 Construction Administration (CA)

• Verify testing agency qualifications submitted by GC.
• Review FF/FL test reports promptly for compliance with specifications.
• Respond to RFIs regarding non-conformance or remediation methods.
• Review documentation of corrective actions and re-testing results before allowing flooring installation.

4.0 Technical Considerations

4.1 Measurement Methodology (ASTM E1155 Summary)

1. Layout: Define test sections and lay out random, repeatable sample lines according to the standard’s requirements (not a uniform grid).
2. Measurement: Use a compliant device (e.g., F-Meter, Dipstick, Digital Profiler like ZIPLEVEL) to measure elevation differences at 1-ft intervals along each sample line.
3. Calculation: Calculate 1-ft (dz) and 10-ft (dZ) elevation differences. Apply statistical formulas from ASTM E1155 to determine FF and FL numbers for the test section.
4. Reporting: Document methodology, raw data summary, calculations, FF/FL results (Overall and Minimum Local), and compliance statement.

4.2 Critical Interfaces & Coordination

• Structural: Consider potential slab deflection (especially post-tensioned) and how it might affect levelness (FL) over time, distinct from initial flatness (FF). Coordinate tolerances with structural engineer.
• MEP: Coordinate locations of floor penetrations, drains (requiring slope, affecting FL), and equipment pads (may have stricter tolerances) before concrete placement. Ensure these don’t interfere with valid FF/FL testing lines.
• Finishes: Ensure specified FF/FL meets or exceeds requirements of sensitive flooring materials (large format tile, thin-set tile, polished concrete, resilient flooring). Remember that additional surface prep (per ASTM F710, etc.) might be needed immediately before flooring, even if FF/FL specs are met.

5.0 Performance Specifications & Acceptance

5.1 Testing Requirements Schedule

5.2 Acceptance Criteria

• Clearly define the minimum acceptable FF/FL Specified Overall Values (SOV) and Minimum Local Values (MLV) per ACI 117 classifications for different areas in the specifications.
• Define procedures for addressing non-conforming areas (e.g., corrective action required, re-testing).

Technical Advisory: Specify more stringent FF/FL requirements (e.g., FF 35/FL 25 or higher) for areas with sensitive finishes (large tile, LVT, polished concrete), critical equipment (medical, labs, data centers), high-speed traffic (AGVs), or high aesthetic importance (lobbies). Consult ACI 117 and manufacturer data.

6.0 Implementation Guidelines

6.1 Example Specification Language (Section 03 30 00)

PART 3 – EXECUTION

3.X FLOOR FLATNESS AND LEVELNESS TOLERANCES

    A. GENERAL: Measure floor flatness (FF) and floor levelness (FL) according to ASTM E1155. Conform to ACI 117 tolerance classifications specified herein.

    B. TIMING: Perform testing within 72 hours after completion of final troweling and before installation of floor coverings or removal of shoring/reshoring.

    C. TESTING AGENCY: Engage an independent testing agency, qualified according to ASTM E1155 criteria, to perform FF/FL testing. Submit agency qualifications for Architect’s review prior to testing.

    D. MINIMUM REQUIREMENTS: Provide floors meeting the following minimum Specified Overall Values (SOV) and Minimum Local Values (MLV):
        1. [Area Description, e.g., General Office Areas]:
            a. SOV: FF [Number, e.g., 25] / FL [Number, e.g., 20].
            b. MLV: FF [Number, e.g., 17] / FL [Number, e.g., 13].
        2. [Area Description, e.g., Areas receiving Thin-Set Tile]:
            a. SOV: FF [Number, e.g., 35] / FL [Number, e.g., 25].
            b. MLV: FF [Number, e.g., 25] / FL [Number, e.g., 17].
        3. [Add other areas as required, referencing drawings if needed].

    E. REPORTING: Submit detailed test reports conforming to ASTM E1155 Section 10 within 48 hours of test completion for each test section. Include floor plans identifying test sections and measurement lines.

    F. NON-CONFORMANCE AND CORRECTION: Areas not meeting specified tolerances shall be identified in the test report. Submit proposed corrective action plan to Architect for review. Correct non-conforming areas using approved methods (e.g., grinding, application of leveling compound) at no additional cost to Owner. Re-test corrected areas to verify compliance.

6.2 Quality Control Integration

• Discuss FF/FL requirements and testing protocols during the pre-construction conference and pre-concrete pour meetings.
• Consider requiring mockups for complex finishes demonstrating substrate preparation.
• Establish clear communication channels for reporting and addressing test results.

7.0 Project Integration & Documentation

7.1 BIM Integration (Optional but Recommended)

• Incorporate specified FF/FL requirements as parameters within the BIM model.
• Potentially overlay digital elevation maps or deviation reports onto the model for visualization and coordination.
• Link final test reports to model elements for facility management handover.

7.2 Required Submittals Checklist

Ensure the following are required and reviewed:

• [ ] Testing agency qualifications and accreditations.
• [ ] Proposed testing plan and sample line layout.
• [ ] Instrument calibration certificates.
• [ ] FF/FL Test Reports (per ASTM E1155 Section 10).
• [ ] Remediation plans for non-conforming areas (if applicable).
• [ ] Re-test reports verifying remediation success (if applicable).

8.0 Specification Checklist for Architects/Specifiers

• [ ] Defined required FF/FL numbers (SOV & MLV) for all distinct floor areas?
• [ ] Specified ASTM E1155 as the testing method?
• [ ] Specified testing timing (within 72 hours post-placement)?
• [ ] Defined testing agency qualification requirements?
• [ ] Detailed reporting requirements?
• [ ] Established clear acceptance criteria?
• [ ] Outlined procedures for addressing non-conformance and required re-testing?
• [ ] Coordinated requirements with relevant Division 01 and Division 09 sections?

Professional Advisory: Rigorous specification and diligent verification of floor flatness are essential components of architectural due diligence. Utilize this guide and referenced standards to ensure clarity, enforceability, and quality control throughout your projects.

For further details, always consult the latest versions of referenced standards (ASTM E1155, ACI 117, ACI 302.1R) and manufacturer literature for specific finishes or equipment.