The county says it needs to complete a storm drainage project.
The entrance gate and the parking lot behind the building at 30 North Market Street in downtown Frederick has been closed. County government officials say a storm drainage improvement project is underway in that area.
The closure is expected to last for two weeks while work is underway.
Residents are encouraged to park in front of the building, or use nearby parking decks.
"County officials apologize for any inconvenience these closures may cause," says a statement from the county.
The building at 30 North Market Street houses the county's Department of Treasury, Community Development Division and other county offices.