Frequently Asked Questions (FAQs)

Areas where homes are spaced further apart and where there is more open space compared to high-density areas like apartments and commercial buildings. These neighborhoods often feature individual houses with front and rear yards and are typically designated as 'low residential areas' on the County's General Land Use Plan (GLUP).

In Arlington County, low density residential areas are primarily zoned R5-20, representing about 50% of the private land. These zones are where impervious surfaces are increasing the most, affecting stormwater and tree impacts.

The County Board directed staff, per their February 2025 charge for the Low Residential Study, not to recommend changes to existing maximum main building footprint or height limits.

Plantable area is the portion of the lot that is suitable for planting trees, in that it has sufficient soil for trees to grow to maturity, without major conflicts with buildings and paved surfaces. Existing trees saved during construction also need this space to protect their roots. Newly planted large canopy trees need at least 1,200 cubic feet (400 square ft, with 3 feet depth), to grow to maturity. Additionally, plantable space needs to be free from conflicts with the building, pavement, fencing, property lines and utilities.

A surface composed of any material that significantly impedes or prevents natural infiltration of water into the soil. Impervious surfaces include, but are not limited to, roofs, buildings, streets, parking areas, pools and any concrete, asphalt or compacted gravel surface.

Yes, any proposed impervious area limits would include the house (building), driveway, patio, walkways, other buildings and surface materials on the lot that significantly impede or prevent water from reaching the underlying ground. 

Under County and State code, paved surfaces constructed with permeable materials and green roofs are considered impervious surfaces for the purposes of stormwater treatment compliance and stormwater utility billing. The main reason for this is because these surfaces displace vegetated surfaces which are considered more beneficial for the environment. Permeable surfaces do, however, receive partial credits for both stormwater treatment compliance and stormwater utility billing. The crediting process ensures that these surfaces receive the maintenance they need to remain pervious.

When zoning regulations change and something that was previously allowed on your property is no longer allowed, the property becomes nonconforming.

 Although the Zoning Ordinance includes lot coverage limits for properties, not all impervious area is categorized as lot coverage. 

Some types of impervious area, such as above-ground swimming pools, at-grade patios and walkways, do not count as lot coverage. These structures and surfaces increase a lot’s impervious area, but they are not subject to the Zoning Ordinance’s maximum lot coverage limits.

In addition, these types of impervious area would not be subject to the County’s stormwater regulations unless the property owner was disturbing more than 2,500 square feet of their lot. Over time, these incremental additions of impervious area have resulted in more stormwater runoff and reduced space for trees.

No. Lot coverage information is not currently tracked by the County.  When the County Board adopted the lot coverage zoning ordinance amendment in 2005, County staff created a web mapping tool that property owners could use to estimate the lot coverage for their individual lot. The web tool used 2001 aerial imagery and 2005 property information from the Department of Real Estate Assessments to generate these estimates. The aerial imagery and property information were not updated to account for demolitions, new construction, additions/expansions and other lot improvements.

The 2005 web tool calculated lot coverage using building footprint, driveway, lot area, and detached garage area data. Thus, the tool only calculated approximate estimates that did not include other lot features that would count toward an individual lot’s total lot coverage. Disclaimers explaining these limitations were included on the mapping tool’s website.

The calculation methodology for lot coverage was further refined in 2014 to codify and clarify which features count and do not count toward lot coverage. Features that were explicitly added as lot coverage in 2014 include:

• Patios > 8 inches above grade;
• Decks > 4 feet above grade;
• Gazebos/pergolas;
• Stoops and landings > 4 feet above grade; and,
• In-ground swimming pools.  

Other features, such as walkways, basement steps, areaways, and window wells, were clarified to be excluded from lot coverage calculations. The 2005 mapping tool was not modified to reflect the calculation methodology changes, nor have staff developed a new tool. 

For several reasons, calculating accurate estimates for an individual lot’s maximum lot coverage limit using GIS is challenging. The variety of features either included or excluded (seen here in ACZO §3.1.4) would require fine-grained, detailed information on these features for each individual lot in Arlington. In addition, certain features are only included in lot coverage calculations if they meet certain requirements for height above grade – measurements which can’t be detected from aerial photography with the precision needed to generate a reliably accurate lot coverage estimate.

Arlington’s Zoning Ordinance requires lots with one-family dwellings to limit the maximum coverage of the lot by the total footprint of buildings and certain paved areas to a specific percentage of the lot's total area. The maximum coverage limit for a given lot is determined by:

• The lot’s zoning district classification;
• Presence of a detached garage; and
• Whether the dwelling has a front porch of at least 60 square feet.

The lot coverage limits include maximum requirements for the size of a main building footprint, measured in square feet. Main building footprints must adhere to separate, but inclusive, maximum coverage percentages.

Read more about how lot coverage requirements are calculated.

One-family dwellings in Residential (R) zoning districts must meet two requirements:

1. A maximum coverage limit for the entire lot; and,
2. A separate maximum coverage limit for the lot’s main building footprint.
   1. The main building footprint limit is included in, and not in addition to, the lot’s total coverage calculation.
   2. The main building footprint includes all parts that rest on the ground, such as:
      1. Attached garages
      2. Bay and oriel windows with floor space
      3. Chimneys
      4. Porches
      5. Decks with floor heights at least four (4) feet above finished grade
      6. Balconies with horizontal projections of at least four (4) feet
      7. Covered breezeways connected to a main building

The following table breaks down the specific coverage limits, which differ based on:

• The lot’s zoning district;
• Whether the dwelling has a front porch of at least 60 square feet (exclusive of any wrap around or side portion); and,
• Whether the lot has a detached garage in the rear yard.

These lot coverage requirements also apply to any one-family dwellings in Multiple-Family (RA), Commercial/Mixed Use (C) and Industrial (M) zoning districts.

A nonconforming property includes a lot, building, structure, and/or use that was legally built, established, and/or created but no longer complies with the current zoning regulations. This can happen for several reasons, but most often a nonconformity arises due to a change to the Zoning Ordinance – including the adoption of stricter zoning regulations.

When a property becomes nonconforming, the property owner is not automatically required to take action to comply with current regulations. Instead, the nonconforming lot, building, structure, and/or use may remain in place as long as the property owner doesn’t add or expand it. In general, the Zoning Ordinance requires property owners to bring their nonconforming property into conformance with current zoning regulations to approve an addition or expansion.

The County’s Zoning Ordinance has been modernized over time to, in part, improve the effectiveness of Arlington’s Comprehensive Plan and other Board-adopted planning policies. Frequently, the County Board amends the Zoning Ordinance to implement recommendations in Comprehensive Plan elements and Area/Sector Plans. New development must comply with the new zoning regulations that align with these policies.

However, the Code of Virginia preserves the rights of property owners to use and maintain their property when newer zoning laws impose stricter standards or even prohibit a certain way they use their property. Numerous U.S. Supreme Court and Virginia Supreme Court decisions over many decades have upheld these property rights.

For these reasons, properties which had previously violated no zoning laws when they were developed are referred to as legally nonconforming when their lot, building, structure, and/or use does not comply with current zoning regulations.

Yes. For many additions and expansions to a dwelling, exceptions in the Zoning Ordinance alleviate residential property owners from bringing their entire property into conformance with current zoning regulations. The addition or expansion may be allowed if it complies with the current zoning regulations. For example, a one-family dwelling that’s located within a required side yard setback can be added to or expanded, but only if the new addition meets all setbacks currently required by the Zoning Ordinance.

Property owners who are considering an addition or expansion of their dwelling should contact CPHD’s Zoning Division at (703) 228-3883 before filing permit applications if they believe their property is nonconforming.

The Zoning Ordinance rules can be found in §16.2. The County provides more information on nonconforming buildings and structures on its website.

In general:

• Property owners can make repairs and interior alterations
• They can repair/rebuild/replace their dwelling in the event of a natural disaster or “act of God,” provided that construction occurs within two years of the event
• Some additions/expansions are allowed by-right
• Some improvements may only be permitted if the Board of Zoning Appeals (BZA) grants the property owner a use permit or a variance.