Although it has been out of service for most of the last 40 years, the old Spring Garden School on 12th Street between Ogden and Parrish Streets holds endless fascination for David Cleghorn.

"It is an incredibly beautiful building," said Cleghorn, senior vice president of real estate development of Help USA, one of the nation's largest providers of affordable housing and social services.

"There are still textbooks from the 1970s sitting on the desks," he said.

The graffiti inside the building is "high-quality street art," Cleghorn said, and "we will certainly try to salvage as much as we can."

That last statement provides a clue to the future of Spring Garden School No. 1, designed by Irwin Thornton Catharine, who from 1920 to 1937 was chief architect of the Philadelphia public school system.

Built in 1927-28, the school, which has been on the National Register of Historic Places since 1986, is a three-story, three-bay brick building in the Moderne style and features a limestone entrance surround, a limestone parapet, and decorative tile.

In August, Help USA began work repurposing the structure into 37 apartments for low-income seniors, with 12 of the units set aside for homeless veterans, Cleghorn said.

The Philadelphia Housing Authority, which owns the building - and, Cleghorn said, had considered razing it as efforts to reuse it fell by the wayside over the years - has leased the school to Help USA for 99 years and is providing Section 8 rental vouchers for all the tenants.

Rent for what is known as Help V is 30 percent of a tenant's income. In the case of many, especially homeless veterans, Cleghorn said, that is "30 percent of nothing." That's where the vouchers come into play.

Those vouchers - historic and low-income tax credits from the Pennsylvania Housing Finance Agency, $1.3 million in small grants, a $500,000 first mortgage, and the generosity ($300,000) of Help USA's board members and others - have helped raise the $13.6 million needed to turn the school into affordable housing, he said.

"Environmental remediation, including asbestos removal, will cost $300,000," he noted, adding that because the building is on the National Register, costly preservation and restoration - scores of wooden windows - will be required.

The building has a fair number of intact original pieces, Cleghorn said. And, best of all, "nothing inside ever got wet."

Each classroom will be an apartment, he said, and the hallways and their marble wainscoting will be incorporated into the interior design.

This is not Help USA's first Philadelphia project. There are four others.

The first two projects, completed in 1999, are on Wyalusing Avenue between 48th and 49th Streets.

One is a 40-unit townhouse complex for low- and moderate-income tenants, many of whom are original renters. The other, across the parking lot and operated by PHA, offers 40 transitional apartments for women and children, he said.

Help USA's third project, completed in 2010, is a 63-unit, affordable rental community for families and disabled veterans at 61st Street and Eastwick Avenue. Also housed there is the Robert G. Brady Veterans Center, which provides office space for supportive services for veterans and families.

The fourth, in the 6100 block of Eastwick Avenue, has 60 apartments for seniors, including those who require permanent supportive housing. Twelve units there are set aside for veterans, Cleghorn said, plus it houses the Hardy Williams Veterans Center.

Help USA's plans for Spring Garden School have gone through a number of transformations since they began two years ago, and financing for what is a very expensive project has been key.

"Philadelphia has been at the forefront of efforts to end chronic homelessness, but the problem remains," Cleghorn said.

The system, however, "is much better," he said.