What is it called when moisture causes wood flooring to expand, resulting in the edges...

Cuppingis the correct term used in the IICRC WRT body of knowledge to describe a condition where wood flooring expands due to moisture, causing the edges of each board to rise higher than the center. This deformation occurs because moisture is absorbed unevenly—typically from below—causing differential expansion across the board’s thickness.

The WRT manual explains that cupping is most commonly associated with moisture intrusion affecting subflooring or elevated humidity conditions beneath the flooring. As the underside of the board absorbs moisture, it expands more than the top surface, resulting in a concave shape across the width.

This condition is distinct fromcrowning, which is the opposite deformation where the center is higher than the edges, often occurring after sanding cupped floors before moisture equilibrium is restored.Bucklingrefers to extreme deformation where boards lift completely from the subfloor, anddelaminationapplies to layered materials separating.

Understanding cupping is essential for restorers because it influences drying strategy, expectations, and post-drying recommendations. The WRT standard emphasizes careful moisture control and adequate acclimation time to allow wood flooring to return as close as possible to its original profile before repairs or refinishing are attempted.