A hearing to decide whether county officials should designate the Bosley Mansion in Towson a historic landmark has been postponed for the fifth time, as the owner waits to finalize the sale of the property to a pair of local developers.

The county Landmarks Preservation Commission had been scheduled this month to consider placing the 19th-century mansion on Baltimore County’s list of historical landmarks, but the hearing has now been pushed to September.

Local developer Marty Azola is a partner in a group working to purchase the property and the mansion, built more than 150 years ago by the Bosley family, one of Towson's early and influential families. He said he’s been consulting with residents and local officials on a plan for the mansion and its 4.4-acre setting.

“The preservation of the mansion and the green space are the two hot buttons with the community,” Azola said. “We’re working with them on both of those.”

Presbyterian Home of Maryland operated a 22-bed assisted-living facility at the property, but relocated the operation last year and put the property up for sale.

Since then, residents in the neighboring Southland Hills community have sought to have the mansion property added to the county's list of historic landmarks — a move that could prevent its demolition or significant alteration in any redevelopment plan. The nonprofit Preservation Alliance of Baltimore County has supported the Southland request.

If the commission places the property on the list of landmarks, any development would be prohibited unless the commission approved it.

Towson-based developer Caves Valley Partners proposed a deal last summer to purchase the property, redevelop it and lease the mansion to Baltimore County for government offices. But residents opposed the deal, and the firm pulled out in January.

Local developers Azola and Delbert Adams stepped in, and Presbyterian Home president Susan Shea and board chair Joseph Slovick asked the landmarks commission to postpone its June meeting due to the pending sale.

In a letter to the commission, they said Bosley Estates LLC — Azola and Adams — was working on a proposal for the property they believe would satisfy neighbors and the Preservation Alliance, “including a plan to preserve the Bosley Mansion.”

Shea and Slovick declined additional comment.

Azola, who has redeveloped other historic sites in the county, including turning the former Towson jail into offices, confirmed last week the group is negotiating the purchase of the property. He declined to disclose the price.

Last year, Azola suggested a plan for a 40-unit condominium at the site. That idea would require a special county review process known as a planned unit development, because the tract is zoned for only 24 residential units. The PUD process allows development outside typical zoning constraints if it will achieve “substantially, higher-quality development” or provide a public benefit.

“It’s the PUD that takes into account what we want, what [residents] want and what zoning, easements and setback can handle," Azola said.

Kate Knott, a member of the Save the Bosley Mansion committee of the Southland Hills Improvement Association, said the association “looks forward to learning the details” of the developer’s plan. She said in a statement that Azola and Adams “are well known for their quality work, historic preservation and adaptive re-use projects.”

Baltimore County Councilman David Marks said residents want to preserve as much of the mansion as possible and its grounds. He noted Southland Hills residents have long used the property as an unofficial community gathering space.

Azola said he is exploring how many units could be created at Bosley Mansion, whether an addition is needed and how best to preserve the yard.

Baltimore Sun Media Group reporter Rachael Pacella contributed to this report.