What is the significance of having a flat subfloor?

Having a flat subfloor is crucial in flooring installation primarily because it prevents uneven wear and lippage in the installed flooring. Lippage refers to the visible height differences between adjacent flooring pieces, which can result in a tripping hazard and an unsightly finish. A flat subfloor ensures that the installed flooring materials, whether they are hardwood, tile, or carpet, sit evenly across the surface. This uniformity helps maintain the integrity and longevity of the flooring, as any deviations in the subfloor can lead to stress points that may cause cracking, warping, or premature wear of the flooring material. Thus, ensuring a flat subfloor is a critical step in achieving a successful and durable flooring installation.