Most household junk and building debris can go in your container. The limits come from the landfill that takes Leesburg loads and from general disposal rules.
The Loudoun County Landfill accepts construction and demolition waste such as lumber, sheetrock, broken brick, shingles, concrete and paving materials. It does not accept anything containing asbestos from businesses, and asbestos siding is refused from everyone. The landfill also turns away land clearing debris, such as stumps and brush from clearing a lot. Commercial loads of dirt, rock, sand or soil aren't accepted either.
Hazardous waste, liquids, paint, solvents, fuel, and asbestos don't belong in a standard dumpster. Refrigerators, freezers, air conditioners and tires carry extra landfill charges and limits, so keep them separate.
Before you load anything you're unsure about, check with your account manager.