The rules change at the county line.

Because three separate governments write them. Virginia sets exemptions statewide through the Uniform Statewide Building Code, so Arlington, Fairfax, and Alexandria all start from the same permissive baseline and localities cannot be stricter on those exemptions. Maryland requires every jurisdiction to use the same code edition but leaves the permit process to each county. DC writes its own construction codes entirely. The result is that the identical re-roof can be permit-exempt on one side of the Potomac and a filed permit on the other.

No, and this is the most expensive misunderstanding in exterior work. Every jurisdiction states that permit-exempt work still has to comply with the building code — underlayment, ice barrier, fastening, flashing, ventilation, and bedroom egress all still apply. What changes is that nobody inspects it. That makes your contractor’s documentation the only evidence the concealed work was done correctly.

All three jurisdictions publish free license lookups. Maryland uses MHIC, Virginia uses DPOR, and DC licenses through the Department of Licensing and Consumer Protection. The thresholds differ sharply: DC requires a Home Improvement Contractor license above $300, Virginia requires a DPOR license above $1,000, and Maryland requires MHIC for residential home improvement generally. Verify the number before you sign, not after there is a problem.

Almost always, and usually it reverses it. Virginia’s state exemptions carry an explicit exception allowing the building official to require permits in historic districts and flood hazard areas. In Alexandria’s Old and Historic district a Certificate of Appropriateness must be in hand before a building permit application can be filed. In DC, historic window and door work needs approval before you apply. Check your address first — approval timelines, not installation, are what drive the schedule on these projects.