What is the rule of 3 in flooring?

A design guideline: keep a home to no more than three flooring materials or tones. The reasoning is that beyond three, a house reads as disjointed rather than designed, and every threshold becomes a visual interruption. A common application is one dominant floor through the main living space, a second in wet areas, and at most a third as an accent. In open-plan homes many designers tighten it further to one or two materials. It is a guide rather than a rule, but limiting materials is one of the cheapest ways to make a house feel more expensive.