The Alexandria City Council voted last night to consider expanding the city's historic district in which tight control is exercised over design of new buildings and renovation of existing ones.

The council was acting on a recommendation from City Manager Douglas Harman, who argued in a memo that some redevelopment projects outside the district "unfortunately lack compatibility with the surrounding areas."

"Many persons can be harmed when inappropriate architectural styles are introduced in historic Alexandria," Harman wrote, urging consideration of the expansion.

Council members gave approval to considering expansion of the district, which already includes much of Old Town, which borders the Potomac River, on the condition that civic and historical groups be consulted.

In 1977, the council voted that specific buildings outside the district could be designated as protected because of special historic interest, and so far, 118 have been so listed.

However, the council has rejected past proposals to enlarge the district itself. Black residents have often opposed the idea on grounds that inclusion of a neighborhood in the district tends to raise property values and drive older black residents out.

Some city officials say attitudes of black residents are changing and that many see historical designation as recognition of their neighorhoods and protection against demolition brought on by Metro redevelopment.

In other action, the council approved in principal a proposal by Mayor Charles E. Beatley Jr. to reduce the size of a Torpedo Factory building that has been scheduled for conversion to a commercial center as part of the ambitious waterfront redevelopment program and ordered further study of it.

Saying that "our view of the river . . . is gradually disappearing," Beatley put forth a smaller-size design of Building No. 10 on the waterfront at the foot of King Street, to expand the view of the river.

Harman pointed out that the design might "change the economics of the building" and urged caution in any design change. Howard Middleton, an attorney for the project's developer, Alexandria Waterfront Restoration Group, said that "it's just not possible now to go back and start all over again."

"We haven't broken any ground, have we?" Beatley responded. The mayor said the city had to take a long-term view, looking 50 or 100 years ahead. "I know that citizens will thank us for opening up a little bit more," he said.

In a roll-call vote, Republican council member Carlyle Ring was the only one to vote no.

The council also endorsed the idea of commuter boat service between Alexandria and Washington and referred the matter to staff for further study. Washington Boat Lines Inc., a tour boat company, has proposed a twice-a-day commuter service.

Ring was the sole vote against the endorsement. He said the service might worsen traffic problems on the waterfront and compete with Metrorail service on which the city has spent enormous sums of money.

The council also voted to give city officials authority to make contact from the start with companies seeking rights to issue industrial revenue bonds. Implementation of the bonds is handled by the Industrial Development Authority, a body independent of the council.