The Fairfax County Board of Supervisors voted this week to increase by 15 percent the number of parking spaces builders must include in new town house developments.

In a special meeting called to resolve the long-debated issue before next week's election, the board unanimously voted Monday to raise the requirement from 2 parking spaces for each town house to 2.3.

But the board rejected the recommendation of county transportation planners that only a fraction of garage space be counted toward the requirement. Some backers of the initiative said that the decision on garage space rendered Monday's action virtually meaningless and was a concession to builders who opposed the plan.

"We still have a problem with town house parking, and I don't think we solved it today," said Republican Supervisor Thomas M. Davis III, who represents the Mason District.

Bob Moore, chief of project planning for the Fairfax Transportation Office, said that only 75 percent of garage space should be counted toward the parking quota because residents often use their garages for other purposes.

The number of cars per housing unit has grown from 1.45 in 1967 to 2.05 today, Moore added.

During a public hearing before the vote, town house residents complained that they have difficulty finding space for their cars and urged supervisors to spare future developments similar problems.

"We are suffering," one Annandale resident said. "The parking problems have been such that we have had scuffles between neighbors."

Developers said the space shortage is not as severe as county officials described, adding that residents have themselves to blame if they convert parking garages to other uses.

"If they're not using their garage to park a car, they're suffering from their own decisions," developer Fred Kober told the board.

Increasing the parking requirement would raise housing costs, he and other developers said.

"You're going to have unused parking spaces that could be landscaping," said Ray Smith, president of the Northern Virginia Building Industry Association. Unused spaces add to the cost of construction, and would therefore drive housing costs up unnecessarily, he said.

County Executive J. Hamilton Lambert disputed the argument that tougher parking requirements would raise housing costs. In the brisk Fairfax housing market, Hamilton said, supply and demand have more effect on prices than construction costs.

The board convened to act on the proposal to prevent it from being deferred until the spring, members said, although observers called it a convenient opportunity for supervisors to appear prudent about growth in Fairfax County.