His business grew until 1910 when fire wiped out the flooring plant entirely. He built a new facility, regarded as one of the most modern plants of the time being built of brick and steel. The initial plant contained two flooring machines (lines) but as business grew, two addition lines were added. In 1914, the kilns at the Reed City plant burned. These were rebuilt and at the same time a new plant was built in Newberry, Michigan. The two plants together had eleven machines. Production ran up as high as thirty-six to forty million feet of maple flooring per year. This represented twenty percent of the total production of maple flooring produced in the United States. In 1919, fire destroyed the entire Reed City plant and in the same year, consumed the dry kilns in Newberry. Undaunted, William rebuilt both plants and production continued to grow. He was regarded as being the largest employer in Reed City, employing upwards of 200 men when the plant was running two shifts. William, was supported in the maple flooring manufacturing industry by his son Sam, who carried on the family tradition for decades.
William Horner died on December 26, 1926 at the age of 74.