The Philadelphia Historical Commission has postponed a decision whether to list three Jewelers Row buildings on the city's Register of Historic Places, leaving the properties vulnerable to demolition as part of a plan for a condo tower on the venerable shopping street.

The Historical Commission voted Thursday to continue for 90 days a decision on the listings for 704  and 706-08 Sansom St. The structures are part of a five-property stretch that Horsham-based luxury home builder Toll Bros. wants to replace with the 16-story condo tower.

The buildings were nominated for listing by the Preservation Alliance of Greater Philadelphia, which aimed to derail Toll Bros.' plan for the 80-unit tower by having the properties designated as historic assets.

In most cases, developers seeking to alter buildings listed on the historic register must prove to the commission that preserving them represents a special hardship.

City officials, however, have argued that a decision to list the buildings would not, under city code, affect Toll's ability to tear them down because applications for the demolition work were filed before the commission began considering the properties for historic protection.

That city position, and the fact that a permit for the properties' demolition had been issued, were cited by the commissioners in their decision to delay a decision.

"Taking an action ... about whether or not a property should be designated when there is a valid permit in place, then all we're doing is muddying the waters and taking a position we have no right to take," said Mike Fink, who serves on the commission as a designee of the Department of Licenses and Inspections.

Tim Spreitzer, a spokesman for Toll Bros.' City Living division, declined to comment about the commission's action.

Preservation Alliance president Paul Steinke said his group would "consider what legal remedies we have going forward" if demolition appeared imminent. He cited a conclusion reached by a Common Pleas Court judge in a similar case this year challenging the demolition of two buildings at 4046-48 Chestnut St. in West Philadelphia.

Historical Commission chairman Robert Thomas said during the hearing that the panel would check in on the Jewelers Row buildings' status when it revisits whether to vote on listing any of those properties.

"We would monitor the situation," he said. "Has the building been demolished? Is it standing?"