I know some of the problem of the cupping is due to humidity, as it flattens out in the winter. But it has spaces almost an 1/8 of an inch. The sub floor is 3/4 plywood t/g, has a crawl space, graveled and plastic over it and pretty dry. Over the sub floor is tar paper as I call it. One of the spaces run the entire length of the house. In the summer it buckles up. The floors were level and dry. Some of the cupping doesn't go away in the winter.