When Jay Madrid built a skateboard ramp in his Arlington back yard last May, he expected most of his visitors to be other teen-age skateboarders -- not the squad of county officials and neighbors who have converged in only slightly smaller numbers.

County building inspectors, zoning inspectors, a planning commissioner and officials with noise-monitoring equipment have flocked to the large yard at 233 N. Garfield St. to view the semicircular plywood ramp that is 28 feet long and rises about 16 feet into the air.

"This has really gotten to be so out of proportion," said Frances Madrid, who, with her husband, John, put up the $1,500 it took for Jay, 16, and some friends to design and build the ramp. The ramp sits in the midst of heavy vegetation and trees, which the Madrids said they thought would screen it from the neighbors.

But the neighbors say it is an intrusion in their peaceful, residential Lyon Park neighborhood. "All of a sudden we've got this monstrosity there," said neighbor Jerome Dick, who is wary that the ramp will attract carloads of other skateboarders. "It's unsightly, it's noisy . . . . I feel it causes a detriment to my property."

"When the ramp is in use, it sounds much like the roar of thunder, not to mention the accompanying yells of participants," neighbor Wendell E. Brown wrote in a letter to the County Board.

To the Madrids, the ramp provides a "structured and wholesome" summer activity that keeps their 16-year-old son at home and away from the dangers of skateboarding on streets and sidewalks.

While 14 of the Madrid neighbors have signed a petition in support of the ramp, the opponents have taken their case to the county, where officials have ruled that the Madrids failed to secure the required permits to build and use the ramp. The Madrids said they did not know a permit was required to build the ramp.

The county's planning staff has recommended that the County Board approve a use permit at its Sept. 7 meeting, noting the ramp is structurally sound, meets "acceptable" noise levels and other requirements. But the county's planning commission earlier this week voted 5 to 3 against recommending a permit because of the neighbors' complaints.

The Madrids are not the first family to find that neighbors object to the skateboard ramps. Similar concerns were raised in a case in Potomac last spring after a back yard skateboard contest drew more than 40 participants from a wide area.

"It's really a frightening undertaking to try to do anything on your property," Frances Madrid said yesterday as she watched Jay do lightning-fast "drop-ins" and "axle stalls" on the board.

Jay Madrid says he is pessimistic about getting a permit from County Board, and believes some of the neighbors' opposition is rooted in the fact that the ramp "is a different thing. No one's seen a ramp before, so it's got to come down."

"This all gets to be a matter of principle when you're talking about what you want to do with your property," said Frances Madrid of the home where her family has lived for 11 years. "But that principle may become secondary to maintaining a happy community."