Jan Z. Krasnowiecki, 90, formerly of Philadelphia, a lawyer and University of Pennsylvania professor who was known as the father of the condominium, died Thursday, Nov. 28, of complications from a stroke at a hospice near his retirement home in Easton, Md.

Born in Krakow, Poland, Mr. Krasnowiecki was the son of Zygmunt and Zofia Krasnowiecki. When he was 10 years old in 1939, he and his parents made a harrowing escape from Poland. Anticipating by two weeks the Nazi invasion, the family walked across the border into Romania and from there made their way to England.

“I was scared as hell as a kid,” Mr. Krasnowiecki told an interviewer for the 1978 Penn Law Alumni Journal. “We were exposed in school to the horrors of war and were compulsorily trained to defend ourselves against gas.”

In England, he attended the Downside School, later Oxford University, Lincoln College. He left England for the United States in 1952 after earning a bachelor’s, a master’s, and a law degree from Oxford.

Once in the U.S., he was drafted into the Army infantry during the Korean War. After his discharge with the rank of sergeant, he completed a master of law degree at Harvard Law School.

Dr. Krasnowiecki accepted a fellowship at the University of Chicago and two judicial clerkships in the Illinois courts before taking a teaching position at the University of Notre Dame. The course was on property, a topic uninteresting to him, but it triggered his study of housing principles that later led to condominiums.

“I never would have predicted this interest when I was at school,” he said.

From 1958 to 1983, Dr. Krasnowiecki was a professor at the Penn Law School. While also teaching, he became a nationally known expert on land use, real estate and housing law, and the development of planned communities such as condominiums.

In 1963 and 1964, Dr. Krasnowiecki was the first to develop the legal documents and arrangements for planned residential developments (PRD), then in their infancy. He wrote and lectured widely on the subject.

“Condominiums are actually a sub-species of the PRD concept,” he said. “The PRD usually involves condominiums or associations of homes clustered around some central facilities.

“Some condominium-type living will be with us, I think, for a long time,” he said. “When it comes to people living closely together for reasons of saving energy and other costs, then I think the condominium is a far superior method of organizing housing than is the landlord-tenant system.”

As a teacher, Dr. Krasnowiecki believed in interaction with his class but not the Socratic method. “I do not confine myself to just questioning,” he said. “I feel that it is my duty to present my own theory.” He wanted to get students enthralled with the topic.

After leaving Penn Law, he became a partner in the Philadelphia firm law of Pepper Hamilton and later in Buchanan Ingersoll & Rooney.

In a local 2002 case, Greaton Properties Inc. v. Lower Merion Township, he represented Merion neighbors opposed to a plan by St. Joseph’s University to use an apartment building it owned in the township as a dormitory for 220 students. The neighbors had lost in lower courts, and appealed to Commonwealth Court.

They argued that the dormitory would create noise and cause parking problems. But the appeals court ruled that the opponents failed to prove that the dormitory would erode the community’s health and safety.

Dr. Krasnowiecki continued to practice law into his early 80s.

His son-in-law, Ron Weikers, said: “He will be remembered for his comforting and sage perspective, his wit and sense of humor, his passion for cooking, his curmudgeonly gentleness, and his love of family and pets.”

He is survived by his wife of 36 years, Carol; daughters Ann Weikers, Sally Pillion, and Molly Shaffer; sons Michael, John, and Matthew; a stepson, Steven Hodges; and 10 grandchildren. He was formerly married to Sara Krasnowiecki. She is deceased.

A service will be held at 10:30 a.m. Friday, Dec. 6, at St. Michael’s Mission Church, 109 Lincoln Ave., St. Michaels, Md. Burial is private.

Memorial donations may be made to the Talbot Humane Society, 7894 Ocean Gateway, Box 1143, Easton, Md. 21601.