Requirements:
The general contractor is responsible for delivering a concrete slab that is both smooth and flat, with a tolerance of +/-1/8 inch in a 10-foot radius. Before installation, the MFMA Sport Floor Contractor must inspect the slab and report any deficiencies to the general contractor or approve the surface if it meets all requirements.
The general contractor is responsible for correcting all deficiencies, including labor and materials. This involves grinding high spots and filling low areas with a suitable leveling compound. The MFMA flooring contractor shall verify that the slab meets flatness tolerance after any corrective action and prior to installation of the floor system.
Recommended Procedures:
MFMA recommends the following procedures be used by the general contractor and concrete subcontractor to ensure proper slab flatness:
- Establish a 5-foot grid across the entire slab surface.
- Use a 10-foot straightedge to check the surface in both directions perpendicular to the grid lines, marking areas needing correction.
Note: A transit or laser alone may miss irregularities between grid points.
- Correct surface variations by –
- Grinding high spots according to ICRI (International Association of Concrete Repair) guidelines to prevent reverse slab curl.
- Filling low areas with a Portland cement-based leveling compound that maintains bond and resists cracking.
Consequences of Non-Compliance:
Failure to meet flatness standards can result in visible defects, reduced performance, and compromised integrity of the wood sport floor system.
FF/FL Numbers:
The MFMA does not recognize FF/FL numbers for athletic flooring, as these metrics do not fully represent slab flatness and may overlook critical surface variations that can affect both appearance and performance of the finished floor.
If you have any additional questions, please contact MFMA’s Technical Director at 888-480-9138.
See Also: Concrete Slab Moisture Content, FF/FL Numbers and Concrete Slab Flatness
Revised 12/2025
© 2015 MFMA
Disclaimer: MFMA provides general information to architects, specifiers, and consumers. MFMA, its members, officers and agents disclaim any responsibility whatsoever for the accuracy or applicability of these guidelines under all circumstances and conditions.