How Do Arlington’s Zoning Laws Impact Residential Architecture?
The Arlington County Zoning Ordinance (ACZO) regulates the size, location, and height of new homes and additions—and even whether a new house can be built at all. A “buildable” lot conforms to current ACZO minimum square footage, average width and street frontage requirements. If your lot meets the current minimums, you are able to build a new home or addition. If a lot does not meet the minimums, it is considered “non-buildable.” New homes are forbidden on non-buildable lots, but additions are permitted if they conform to the current ACZO. There is, however, one loophole: if a non-conforming lot’s deed was recorded prior to July 1950, then it is considered grandfathered and new construction is allowed.
The ACZO regulates building size via house footprint and lot coverage. The house footprint includes the house itself, roofed porches, attached garages and taller decks. Each zoning district has different maximum house footprint ratios (percentage of the lot area). Each district also has a different maximum house footprint cap (square feet). The proposed house cannot exceed either the ratio or the cap. Lot coverage includes the house footprint plus the driveway and any accessory structures (i.e. detached garages). Each district has a maximum lot coverage ratio (percentage of the lot area). Because the County wants to promote traditional residential streetscapes, the ACZO gives bonus coverage for both the house footprint and lot coverage if homes include front porches and/or detached garages.
The final piece of the ACZO puzzle is the 35’ height limit in residential districts. This is the measurement from average grade to roof midpoint height. Average grade is the mean elevation of the land abutting the structure. Both existing and proposed grades must be measured. The roof midpoint is measured (vertically) between the peak and soffit of the main roof.
Tripp DeFalco has been designing and building in Northern Virginia since 1993. A licensed architect, he is a member of the American Institute of Architects and is nationally certified by NCARB. Over his 30-year career he has designed more than two hundred residential projects, ranging in value from $100k to over $5 million.
Awards/Honors:
Bachelor of Architecture, Syracuse University
Licensed Architect, VA & NC
NCARB Certified to practice nationally
25 years practicing as an Architect
10 years managing a Design/Build firm
Arlington Magazine Winner, Best Architect 2022 & 2024