Factors Affecting the Expansion of Hard Maple Flooring

Three different investigations were conducted. The first was specifically concerned with the relative expansion of hard maple (Acer saccharum Marsh.) flooring panels having strips of different widths subjected to humidity conditions which were to produce an equilibrium moisture content of 15 percent. Secondary considerations were the expansion-retarding effects of such techniques as preboring and the use of a mastic vapor barrier between the finish floor and the subfloor. The results of the first study showed an increase in overall expansion of the flooring as the width of the flooring strips was increased. Total expansion of 2-1/4-inch strips exceeded the expansion of 1-1/2-inch strips by about 100 percent, while expansion of the 3-1/4-inch strips exceeded that of 1-1/2-inch material by 130 percent. No significant difference occurred in the expansion of a flooring panel using a mastic vapor barrier when compared to flooring laid over waterproofed building paper. Preboring resulted in a reduction in overall expansion of 10 percent which was not considered significant. A second investigation dealt with the lateral resistance of 2-1/4-inch cut nails with and against the nail angle. Four-inch lengths of 2-1/4-inch maple flooring were fastened with a single cut nail driven at a 50? angle into sections of a southern pine joist. A second grooved strip was then butted against the nailed tongue so that lateral loading could be applied to the nail from either direction. Average lateral resistance in the direction of the 50? nail slope was 384 pounds per nail while in the opposite direction it averaged 363 pounds. The third investigation dealt with buckling, a condition caused by swelling of flooring strips and loosening of the nails. A series of compression tests were performed on small flooring panels having conventional and modified joints. The average stress required to buckle conventional flooring strips was 946 psi, and for the modified flooring, 1,396 psi, illustrating the superiority of the modified joint.

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