The Montgomery County Planning Board has refused a request by International Business Machines Corp. to build a parking lot that is smaller than mandated by the county for the company's Gaithersburg building.

IBM, which received permission in February to expand its existing Gaithersburg complex, wanted to increase the number of parking spaces in the surrounding lot to just more than 2,000 spaces instead of the 3,000 required by county law, said Douglas Alexander of the county's urban design office.

He said the county determines parking needs for all office development according to square feet of office space.

"IBM argued that their building was different because it has a substantial amount of computers and a large cafeteria," Alexander said. "They had based their 2,000-space lot on the number of employes, not the amount of floor space."

The planning board, however, ruled that everyone must abide by the rules. Alexander said that board members felt IBM's claims were not properly substantiated and worried that other developers might try to use any precedent to bypass the parking lot requirement.

"The county hesitates to make exceptions because it leads to problems with other developers down the road," he said.