A century of snow and summer sun has warped the hand-fitted sideboards of the tiny chapel that overlooks Old Columbia Pike just north of East Randolph Road in Montgomery County. Its white paint is flaking and its asbestos roof spotted with moss. Plastic sheeting fills in for a rose window pane shot out by a BB gun 15 years ago.

To the Rev. Paul Mericle, rector of St. Mark's Episcopal Church, the 1877 structure is just "a cute little white church" that is beyond repair and too expensive to heat. He'd like to tear it down to clear a view of the congregation's brand new brick meeting hall to the rear.

But to the Montgomery County Historic Preservation Commission, the chapel, now used as a parish storehouse, is a prime specimen of "Country Gothic," an architectural style popular in American villages of the 19th Century.The commission wants the chapel, together with a much larger wing added in 1927, declared a historic site.

If it were, the commission would have the power to veto demolition and alterations and order repairs. Fines of $500 per day could be levied for disregarding commission instructions. As a last resort, the building could be seized and sold to parties who would care for it as the commission feels is proper.

All of which has Rev. Mericle up in arms. Historical designation is an "invasion into private property," he argues. What's more, there's the larger question of separation of church and state: "If we allow the government to come in and tell us what we can do with our building, then they are controlling the church."

Mericle estimates it would cost $50,000 to replace the rotten wood of the chapel. In addition, it needs new paint and possibly a roof. Currently saddled with a $250,00 mortgage on the new church, the congregation simply can't afford to maintain "art museums," Mericle says.

Details may differ, but complaints such as Mericle's are common in Montgomery County these days as a result of a new historical preservation law passed in 1979. The law gave the county government its first real power to defend its architectural heritage from subdivision sprawl and road development.

Commission officials estimate that owners of about 40 percent of the property considered so far have welcomed the designation. But an equal number see it as a new layer of government interference and the rest don't care.

Jean Richelsen, for example, a Silver Spring woman who inherited a dere;oct 1850 log cabin located in Germantown, protested to the county council when the cabin was declared a historical site. Richelsen and her husband testified that they should not be forced to repair the cabin themselves and offered to donate it to the county. "They simply said there was no money for that," she said.

While the forms often differ, most jurisdictions in the Washington area now have some sort of preservation legislation. Prince George's County is currently considering a law similar to Montgomery's.

Over 1,000 sites will eventually be considered for designation under the Montgomery County law. The nine-member commission reviews sites at Thursday night sessions and recommends them to the county planning commission, which forwards them to the county council, where the ultimate decision is made.

So far about 80 sites have been approved, with about 100 more under active consideration. Once a site is designated, the owner must get clearance from the commission before undertaking major alterations to the property or demolition.

The commission can invoke powers to stop "demolition by neglect" and order repairs or have the repairs made and bill the owner. Default on such a bill can lead to the property going up for public sale.

Buildings can be designated historic for having had an illustrious occupant or event in its past. The status can also result if the structure is deemed a "familiar visual feature of the neighborhood" or, as in the case of St. Mark's, a specimen of a building style of bygone years.

According to the commission, the chapel is "an example of a highly stylized rural or country church and it is representative of the Gothic Revival style of architecture." It has false buttresses outside, pointed arches, stained glass and, over its main door, a simple rose window.

Eileen McGuckian, the commission chairwoman, notes it also has original materials such as board siding and field stone foundations. "It's rather difficult to go through 100 years and stay in original condition. But this church has done that," she says.

To help property owners maintain their buildings, the county has access to $70,000 in federal funds, but 15 applicants have submitted requests totalling more than three times that sum. A tax incentive program for owners is also being devised, McGuckian said.

Mericle, meanwhile, plans to show up with his congregation as the County Council decides on his chapel Thursday. He says he would gladly give the chapel to the county as long as his congregation doesn't get stuck with any costs.

"If the county is so desirous of this church," says Rev. Mericle, "take it, get it away from here."