Thirteen months ago a Montgomery County government board decided that a new office building in Silver Spring was too tall and demanded that its top floor and penthouse be torn down.

Today the $2.4 million structure is as tall as it was, but vacant and little more than a "home for pigeons," according to a spokesman for the owners, who are pursuing the matter through the courts.

Joseph R. Blocher, a lawyer who represents the Permanent Financial Corp., owner of the structure at 801 Wayne Ave., asked the Maryland Court of Special Appeals last week to overturn a Sept. 30, 1983, ruling of the Montgomery Board of Appeals.

In its ruling, the appeals board turned down the owner's request for a variance for the office building that exceeds county height and size limits.

As a result, the building permit for the unfinished structure was suspended, preventing completion of the interior. "The building has been vacant since then, a home for pigeons," said Blocher.

The appeals board ruling touched off a costly legal battle over the future of the building's top floor and penthouse. Montgomery Circuit Court Judge Stanley B. Frosh rejected Blocher's first appeal; the Court of Special Appeals, Maryland's second highest tribunal, will hear the case in January.

In the meantime, negotiations between Blocher and county officials for an out-of-court settlement have stalled, both sides said last week.

"The door has been open for negotiations, but I don't think there's any way to settle it without removing the penthouse," declared Clyde C. Henning, the county government attorney who is handling the case. "The county government has a legitimate interest in preserving its zoning ordinance. We're not being just hypertechnical bureaucrats saying, 'You goofed, now tear it down.' "

The Wayne Avenue building is 53 feet tall, including the penthouse. Montgomery officials contend it should be only 35 or 43 feet tall, depending on whether they allow rooftop structures such as air-conditioning vents or an elevator shaft structure.

Blocher has argued that not only did Montgomery inspectors certify the design, but also that the county changed crucial building regulations before the building was finished. "We're not going to strip it down," Blocher said of the contested floor.

He added that the legal snarl has led to "a waste of time, money and resources. Only in Montgomery County would something like this happen."