County Low Residential Study

What is Arlington's "Low Residential" Study?

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Arlington County is studying whether to set a first-ever maximum allowance to limit the amount of Impervious Area (IA) on redeveloped properties in low residential zoned areas of the County (which are zoned as "R" and "RA" districts). 

 

This would help address goals contained in the Forestry and Natural Resources Plan (FNRP), Chesapeake Bay Preservation Plan, and Stormwater Plans, all elements of the County's Comprehensive Plan.  The County hopes reducing IA will help control stormwater runoff that causes flooding, erosion, and poor water quality in the Bay, and reduce tree loss that impedes the FNRP 40% tree canopy goal.  (NOTE:  a canopy of approximately 50%-55 % in the "low residential" areas as the County terms it is necessary to average out the low canopy cover in transit corridors.)  

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What Will the Study Do and What is the Timeline?

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The County for years has acknowledged critical flooding and tree loss, identifying new home "footprints" on residential lots as the core problem.  As late as December 2023 it therefore agreed - with strong support of the Forestry and Natural Resources Commission and others - to study existing standards for dimensional "lot coverage" standards as these are currently fairly well understood in the community.  These include: 

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• maximum height for buildings;

• maximum house footprint (which, together with height, limits limits the overall size of the house);

• minimum building setbacks from lot lines; and

• max. overall lot coverage (which includes the house footprint, driveways, detached buildings, pools, sidewalks, etc.)

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In November 2024, new findings on the tree canopy and higher flood risk prompted the first meaningful review of lot coverage since 2005.  In early 2026 however, the Board changed tack and directed staff NOT to study reduced footprints or zoning lot coverage, but instead to look at capping impervious surfaces.  By September, staff indicated they would move away from the dimensional lot coverage and present the Board with three caps on impervious areas, as a new control. 

 

ASF believes the Board should revert to study zoning dimensional standards, as much simpler, and more comprehensible for residents and builders.  Staff is also proposing that EACH of three new IA caps would exceed the current median lot coverage for all lots in Arlington.  Staff has not yet demonstrated or quantified how or how soon new guidelines would slow tree loss and flooding, nor whether they would shrink home footprints or even reduce runoff.  See County's latest proposals here.  The R-6 zone, which covers the largest percentage of all low density residential zoned land, currently has a median IA coverage of 35%, and the County as of September 2026 is proposing new caps of 40%, 45% or 50% respectively. 

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ASF believes the County should have provided information on average lot coverage of homes built since 2005 (i.e. just the newer, larger homes), and to reduce IA from that level by 10%, 15% or 20%.  ASF believes the Board should revert BACK to the zoning dimensional standards, as much simpler, and more comprehensible standards than IA.  Indeed, the incredibly dense study data (139 pages), the poor analytic approach and low awareness in the community will guarantee inferior outcomes that may well have no real effect on tree canopy or runoff.  In fact, the county indicates that preserving and planting more trees will still be critical, thus already undermining much of the work that has been invested in the LRS. 

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What Does Overgenerous Lot Coverage Look Like? ASF Before and After Images

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Below we show lots where developers swapped out modest-sized homes for structures more than double the size, a phenomenon that exacerbated tree loss and stormwater runoff.

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