The short answer depends on one question: are you changing the size of the opening?
Montgomery County, Maryland
The Department of Permitting Services lists windows and doors that keep the same opening size and net clear opening among work that generally doesn't need a building permit. Enlarging an opening, cutting a new one, or changing a bedroom window's clear opening does.
- City permit offices: Rockville and Gaithersburg issue their own building permits.
- Historic districts: parts of Bethesda, Chevy Chase, Kensington, Takoma Park and other areas need historic preservation review for exterior changes.
- Basement bedrooms: egress windows have minimum opening and sill height rules and need a permit.
- HOAs: covenants are separate from county rules.
Washington, DC
Permits come from the DC Department of Buildings, and large parts of the city are historic districts with their own review. Check the address before choosing a product.
Northern Virginia
Each county and city sets its own permit rules. Contractors need a Virginia DPOR license for jobs over $1,000.
Houses built before 1978
Federal EPA rules require lead-safe certified renovation practices when old windows and doors are removed.
Check your contractor's license
In Maryland, home improvement contractors must hold an MHIC license. Ask for the number and look it up before signing.