How flat does a concrete slab need to be for a hardwood sports floor?

The slab must be within the flatness tolerance stated in the current installation instructions for the selected hardwood sports floor system. There is no reliable universal number that applies to every system, measurement length, or project.

Flatness matters because high and low areas can affect support, panel or subfloor contact, movement, installation accuracy, and the uniform performance of the finished court. A slab can appear visually smooth while still falling outside the required tolerance. Flatness should therefore be measured systematically with the method and reference length specified for the system, not judged by eye.

Complete moisture, strength, cleanliness, and level surveys before materials arrive. Record the results and agree on any grinding, leveling, or repair work before installation begins. Do not assume that the sports floor will bridge unacceptable slab variation. The designer, flooring manufacturer, and qualified installer should confirm the applicable tolerance and preparation method for the chosen build-up and project conditions.