Roofing problems. Units with “Sagging roof”, “Missing roofing material”, or “Hole in roof” were classified as having Roofing Problems. A “sagging roof” is a critical defect indicating continuous neglect, or deep serious damage to the structure. Only roofs with substantial sagging were included. “Missing roofing material” includes rotted, broken, loose or missing shingles, tiles, slate, shake, and tin, caused by extensive damage from fire, storm, or serious neglect. “Hole in roof” occurs when the missing roof materials expose the interior of the unit directly to weather. Holes caused by construction activity were not counted unless the construction had been abandoned.