When you install a floor, it may look good for a while, but it may not stay that way forever. A big factor in the lasting quality of your floors results from the unseen subfloor. Subfloors give floors extra support. They attach to the flooring material, making them strong enough to support the weight of furniture, appliances, and traffic. Building codes determine the spacing and spans for subfloor installations. However, doing the bare minimum does not always give you all the support you need. Shortcuts in subfloor installation may lead to the dreaded squeak.