The Chattanooga Housing Authority is closing its waiting list for scattered-site housing, leaving 348 people on the list and saying it may take 10 years to get all those people into housing.

On Tuesday, the authority had only 18 units ready for occupancy out of a total of 3,025 in all 17 of its complexes, whether they were scattered-site — complexes built with fewer residences — or larger family housing complexes, officials said.

Another 207 units are in “various stages” of being repaired or cleaned, but officials cannot say when those apartments will be available.

“My sense is that we’re in difficult economic times, and the need for affordable housing is higher than it has ever been since the inception of the Public Housing Act in 1937,” said Bill Lord, the housing authority’s chief information officer.

Of the housing authority’s housing sites, six of them are scattered-site developments, including complexes such as the Woodside Avenue Apartments and Gurley Street Apartments, both of which have 24 units. In comparison, College Hill Courts has 497 units and is known as a public family housing complex.

Eighty-one units of scattered-site housing now are occupied and no more are available, housing officials said. Such units generally turn over about 31 times a year, so it could take more than a decade to house all the people on the waiting list, said Bryant Lowery, the housing agency’s director of asset management.

The wait may be longer if the housing authority receives permission from the U.S. Department of Housing and Urban Development to demolish apartments on Fairmount and Gurley streets. The apartments, both in North Chattanooga, account for two of the authority’s scattered housing sites.

Housing officials said both sites, which total 52 units, functionally are obsolete and that it would cost up to $150,000 per unit to renovate them.

The need for more affordable housing is a problem nationwide, said Sue Popkin, principal research associate with the Urban Institute, a Washington, D.C.-based nonpartisan research institution.

“There’s not enough housing assistance to go around to all the people who need it — ever,” Ms. Popkin said.

The rule of thumb is that about one-third of the people who are financially eligible for public housing get it, she said. It’s not like Medicaid or food stamps, and people don’t automatically get public housing even if they qualify, she said.

“(Getting housing assistance) is basically a lottery,” she said. “People wait and, if they haven’t found something else by the time their number comes up, then they get housing,” Ms. Popkin said.

Bonita Johnson heads one of about 16 families that live in the Fairmount Avenue apartments. Being smaller, scattered-site housing has less crime, said Ms. Johnson, who has lived in the Fairmount Avenue apartments for more than 30 years.

“It’s a smaller development, and you can better contain who goes in and who goes out,” she said. “You may find people who let people who sell drugs move in, but you can tell them that we are not going to have that and they listen to you.”

In January, the housing agency closed its waiting list for Housing Choice vouchers, formerly known as the Section 8 program, with 3,500 people waiting for housing.

“We’re at a maximum,” said Eddie Holmes, chairman of the housing authority’s board. “The housing authority cannot be the sole provider for affordable housing. The need is too great.”

Mr. Holmes applauded agencies such as the 28th Legislative District Community Development Corp., which has built 50 affordable housing units since 1997, and the Chattanooga Community Housing Development Organization, which has built 15 to 20 affordable homes in the past five years.

However, more entities need to be doing the same, he said.