From dry rot and sagging or rusted roofs to uneven or cracked foundations, the conditions of many homes in many neighborhoods throughout Gainesville is a glaring and aching element of the city’s affordable housing crunch. Of 447 residences recently surveyed across portions of two census tracts in the city, 62 percent had at least one minor defect, while 14 percent, or 62 homes, had a major defect. “Just walking through the neighborhoods ... I think there are more pockets of housing that are in decline than we expected,” said Kim Skobba, assistant professor in the housing management and policy program at the University of Georgia.