Systems and methods for forming fiber webs, including those suitable for use as filter media and battery separators, are provided. In some embodiments, the systems and methods involve a first system for forming a fiber web (e.g., a wet laid system or non-wet laid system) and additionally one or more coating units. The first system for forming a fiber web may be used to form one or more fibrous layers of the fiber web, and the coating unit may be used to form an additional fibrous layer of the fiber web. In some embodiments, the systems and methods can be used to form fiber webs having a gradient in a property across a portion of, or the entire, thickness of the fiber web.