Minarda Pimentel had to keep her clothes in sealed plastic bags because rats gnawed on everything in her closet.

Her neighbor Dominga Sanchez had to boil water on the stove for showers because there was no hot water — or heat for that matter — for days at a time. Ms. Sanchez’s oldest daughter moved out because the mold on the walls made her sick.

Their hardship stories are common enough in the low-rent neighborhoods of the Bronx, where dilapidated buildings are often passed from one neglectful landlord to the next. But the tenants of this decrepit apartment complex on College Avenue, many of whom speak little English, finally decided that they had enough.

Behind their creaky, peeling doors, they embarked on a yearlong campaign against their landlord that attracted the attention of influential supporters and eventually led to a change in ownership.