The daughter of a former Democratic vice presidential nominee is seeking to enlarge her recently purchased West Village townhouse by more than a third, but neighbors say the proposed expansion into a shared internal courtyard will be an infringement on them.

Geraldine Ferraro’s daughter, Donna Ullman, told The New York Sun that the proposed addition is designed to add living space and an elevator to the townhouse with the anticipation that Ms. Ferraro may eventually live there. Ms. Ferraro served three terms in Congress, was Walter Mondale’s running mate against Ronald Reagan and George H.W. Bush in 1984, and twice ran unsuccessfully for Senate. She has been battling with multiple myeloma, an incurable blood cancer.

Ms. Ullman and her husband, Paul Ullman, applied to the Department of Buildings in December for a permit to add nearly 1,400 square feet for an “enlargement and conversion of an existing two family to a single family residence.”

The existing three-story Greek Revival style row house was built in 1841. It is 3,480 square feet, according to city records. Ms. Ullman and her husband purchased the property in November for $3.75 million. The proposed addition would cost an estimated $525,000.

Neighbors said they are concerned that the large rear addition will interfere with an open courtyard that contains some shared space. They said that if the project is approved, a precedent will be set and large rear additions will begin to flood historic courtyards around the neighborhood.

Ms. Ullman said the opposition is limited to her immediate neighbors, who she said are only worried about the potential loss of light in their own rear additions. Ms. Ullman said she has received more than a dozen letters of support from buildings in the neighborhood.

“What we’re doing actually has several precedents right within the immediate area,” Ms. Ullman said. “This isn’t precedent setting by any stretch of the imagination. We are doing nothing different than what several other neighbors have already done.”

The executive director of the Greenwich Village Society for Historic Preservation, Andrew Berman, said he has met with both the applicants and concerned neighbors, and his organization has not yet determined whether it will take a position on the proposed expansion.

Mr. Berman said rear additions in the Village are becoming more frequent and more ambitious in size.

“It’s an issue that requires attention. Rear space certainly has an impact in the quality of life for neighbors and affects neighborhood character,” he said. “But it’s a fine line to walk. It is private space, the public does not have access to them visually or otherwise, so where do you draw the line for what is appropriate?”

Because the three-story townhouse falls within the boundaries of the Greenwich Village historic district, the project must be approved by the city’s Landmarks Preservation Commission, as well as receive standard zoning approval by the Department of Buildings.

The Landmarks Commission has determined that the application must proceed through a public hearing process, and a hearing is scheduled for March 7.

The concerned neighbors said they would attend a local Community Board 2 meeting on Monday that will address the proposed expansion. The Community Board will send an advisory recommendation to the Landmarks Commission.