Let us now imagine that the ambient humidity goes down to 25%. The moisture content in the boards will decrease to 5.4%, a loss in MC of 1.5%. The flooring boards will contract 0.0138 each, and gaps will appear between each row. For a ten-foot stretch of flooring, the contraction represents more than 5/8" or 1.6 cm.

48 boards x 0.0138" = -0.6624" (-1.68 cm)