County Staff Report
DRAFT INFILL RESIDENTIAL DEVELOPMENT
Maximum Lot Coverage
March 9, 2001

MAXIMUM LOT COVERAGE

The Zoning Ordinance amendments considered in this report would change the maximum permitted lot coverage for all one-family residential lots in "R" Districts. In addition, related changes are proposed in Section 1. Definitions and Section 32. Bulk, Coverage and Placement Requirements, Subsection 32.C. Coverage of the Zoning Ordinance, to update and clarify the intent and requirement for lot coverage.

The proposed Zoning Ordinance amendments for lot coverage are the third item in a series of Zoning Ordinance amendments, which have been studied during past several years. These amendments were proposed in response to the issues raised by recent infill one-family residential developments, including new construction and an addition to existing houses. Issues raised by the community and the ZORC, Principles, the proposed three options, along with discussions and a preliminary staff recommendation are described below. The proposed Zoning Ordinance amendment language for three Options is also included in the report. The remaining Zoning Ordinance amendments for infill-residential development would address issues related to pipe-stem lots, and are scheduled to be considered by the County Board and the Planning Commission in the summer of 2001.

Background:

History of Lot Coverage Ratio in the Zoning Ordinance: The County Board adopted the first lot coverage restrictions in the Zoning Ordinance in 1942, and then amended them in 1960. Before 1942, the Zoning Ordinance did not include lot coverage restrictions. The placement of buildings, including accessory buildings, was regulated by front, side and rear yard requirements at that time. In 1964, the County adopted a Zoning Ordinance amendment establishing the current 56% lot coverage requirement for all zoning districts in the County.

The table below shows the maximum permitted coverage ratios before 1964. The lot coverage ratios between 1942 and 1960 included all buildings (main buildings and accessory buildings) in regulated covered areas.

Since 1994, the County Board and the Zoning Ordinance Review Committee (ZORC) have been reviewing one-family residential development related regulations in the County. Chronology of the major events are:

• 7/9/94: The County Board held the first work session for one-family residential development related regulations. At the Work Session, the County Board requested that the Zoning Ordinance Review Committee (ZORC) and staff review the issues raised by recent one-family residential developments.
• 7/19/97: The County Board adopted the Zoning Ordinance amendments for Unified Residential Development (URD) provision.
• 4/10/99: The County Board adopted a Subdivision Ordinance amendment related to the URD provisions.
• 5/11/98, 11/12/98, 7/26/99, and 5/9/00: The County Board held three work sessions for the Infill-Residential Development.
• 8/1/00: The County Board adopted Zoning Ordinance amendments for building height.10/7/00: The County Board adopted Zoning Ordinance amendments for average lot width.
• 11/18/00: The County Board adopted the Zoning Ordinance amendments for building placement.

Lot Coverage Requirements in the Current Zoning Ordinance: Currently the Zoning Ordinance permits maximum lot coverage of fifty-six percent (56%) in all residential and commercial zoning districts in the County. Only exceptions are in RA7-16 and RA4.8 districts, where the permitted maximum lot coverage ratio is fifty percent (50%). Subsection 32.C.Coverage of the Zoning Ordinance describes the purpose of establishing the maximum lot coverage, and sets fifty-six percent (56%) as a maximum lot coverage ratio.

Current Language for Coverage:
For the purpose of securing open space for the exclusive use of pedestrians, except by site plan approval, no building or structure in "R," and "RA," and "C-1-O" Districts, including accessory buildings and all areas for parking, driveways, maneuver and loading space, shall cover more than fifty-six (56) percent of the area of the lot, except as may be specified in the various district classifications.

Data on Lot Sizes: There are a total of 28,709 lots located in R-5, R-6, R-8, R-10, and R-20 Zoning Districts in February 2001. The table below shows the number of lots in each zoning district by lot areas. The table shows that, in R-10 and R-20 Districts, large percentages of lots are in a close range to the required minimum square footages for each respective zoning district. In R-10 Districts, 72% of the lots are within a range between 10,000 square feet and 19,999 square feet. In R-20 Districts, 93% of the lots are over 20,000 square feet. However, in R-5, R-6, and R-8 Districts, significant numbers of lots are larger than the required minimum lot areas. In R-5 District, only 24 percent of the lots are in a range between 5,000 and 5,999 square feet, and 79% of the lots are larger than 5,000 square feet. Comparable numbers are 49% and 77% for R-6 District and 45% and 81% for R-8 District.

Lot coverage data from the recent examples of one-family residential developments are as follows:

The lot coverage data based on the diagrams prepared for two prototypical site layouts are as follows. These are for a one-family house with an attached two-car garage and for a one-family house with a detached two-car garage. See the attached diagrams. On a 5000 square-foot lot in R-5 District, if a garage is attached to a main building, only a maximum coverage ratio of 44 percent can be achieved because of building placement regulations, such as front setback, side and rear yard requirements.

Average new one-family houses in 1999: The nation-wide data provided by the National Association of Home Builders (NAHB) shows that new one-family houses contained 2,250 square feet of floor area on average in 1999. A median floor area was 2,030 square feet. There are no comparable data for the Washington Metropolitan Area, but it can safely be assumed that the average floor area for the region was no smaller than the nation-wide figure. Eighty-one percent (81%) of the new houses built in 1999 had garages with a capacity for two or more cars. Fifty-one percent (51%) of the new houses built in 1999 had two or more stories.

According to the NAHB data, an average one-family house would be a two-story house with a floor area of approximately 1,100 square feet per story and a 400-square foot of parking garage. When a 5,000 square-foot, which is a minimum lot area in the R-5 District, is developed with a main building of this size and a detached parking garage, a lot coverage ratio of 50 percent would be required. The table above indicates that, on any of the R-6, R-8, R-10, and R-20 Districts, a house with a ground floor area of approximately 1,100 square feet and a 400-square foot parking garage, either attached or detached, can be placed on minimum size lots under the proposed lot coverage ratios.

Guidance from the County Board and the ZORC: Guidance from the County Board provided at the County Board Work Session on July 26, 1999, and from the ZORC at a series of monthly meetings were:

1. Total coverage should include building footprint, parking areas and driveways. To the extent possible, patios and interior walkways should not be counted.
2. Revise the intent/preamble of the section for coverage, which is outdated, and/or add definition of coverage.
3. Generally support reducing overall maximum lot coverage. Needs to explore establishing maximum lot coverage ratios for buildings, in addition to total lot coverage ratios. But, would like to see effects of separating building coverage from other types of coverage
4. Sliding scale for different R Districts needs to be explored.
5. Needs to explore how reduced coverage would affect properties.
6. No interest in requiring percentage of open space on one-family residential lots.
7. Revised coverage ratios should not interfere with the ability of Arlington builders to compete in the market place.
8. Revised coverage ratios should not interfere with the ability of residents to make reasonable size additions.

Interrelationship of Lot Coverage with Other Issues Being Studied:

All Options A, B and C are revisions to the maximum ratio permitted for lot coverage, and would not change the basic definition of lot coverage, which is currently defined as footprints of all buildings or structures, including accessory buildings, parking pads and driveways. These changes are generally independent from the previous Zoning Ordinance amendments for building height and lot coverage. The fourth amendment proposed for pipestem lots is not finalized yet. There is some possibility that pipestem lot related amendment might interact with the proposed amendment for lot coverage. However, that issue will be resolved at the time when pipestem lots are studied.

Other jurisdictions:

In the Washington Metropolitan Area, some jurisdictions set maximum lot coverage ratios. Some jurisdictions, however, have no lot coverage ratio requirements, and building placement was regulated by setback and yard requirements. Examples of the lot coverage requirements, including definitions are as follows.

Definitions of lot coverage:

Fairfax County: Determined by dividing that area of a lot which is occupied or covered by the total horizontal projected surface of all buildings, including covered porches and accessory buildings, by the gross area of that lot.
Prince William County: The area of a lot occupied by structures, off-street parking, driveways, outside storage, or any other improvements not considered open space.
City of Falls Church: Lot coverage will be determined by "all buildings" and does not include parking pads or driveways.

Zoning Ordinance Review Committee:

The ZORC studied these three maximum lot coverage options at many regular meetings between November 1998 and the present. Their inputs are well incorporated into the descriptions, comments and recommendations concerning these three options. Its final comments for this report would be added later after the February 26, 2001 ZORC meeting.

Community Outreach:

Representatives of the ZORC and staff made several presentations for the proposed infill residential development related Zoning Ordinance amendments at community meetings including the Neighborhood Conservation Advisory Committee (NCAC). The most recent presentation was made at the April 6, 2000 NCAC meeting for building height and average lot width. The ZORC and staff will continue this effort to keep informing the community about the progress of this project and seek their input.

Issues raised by the Community:

1. Size and compatibility of new houses with existing houses. New one-family houses tend to be larger, bulkier and taller relative to their lot sizes and to the sizes of existing houses in the surrounding neighborhoods.
2. Perceived loss of open space.
3. Loss of privacy in surrounding houses.
4. Loss of light, air circulation and planting areas.
5. Water run-off problems caused by too dense or inappropriate site design.

Principles:

Staff developed the following principles based on the discussions held with the County Board and the ZORC.

1. Reasonable smallest coverage ratio: Permit the smallest reasonable coverage ratio to preserve green space, light, air circulation, and privacy, while permitting new construction of or building additions to existing houses of average size houses in the current housing market. Reducing the maximum lot coverage permitted by the Zoning Ordinance should not create large number of nonconforming lots.
2. Control "oversized" houses: Control "oversized" houses relative to other houses in the neighborhood, including the houses located on oversized lots relative to the applicable zoning Ordinance requirements.
3. Minor changes and additions: Leave room to allow minor changes and additions to existing houses.
4. Zoning Administration: The lot coverage regulations should be simple and easy for citizens to understand and for the Zoning Administration staff to administer.

Proposed Options:

The following maximum coverage ratios were discussed at the July 26, 1999 County Board Work Session. Among these options, Options A and C were eliminated because the ZORC and staff agreed that establishing two coverage ratios, one each for a total coverage ratio and for buildings or a main building, would be too cumbersome to administer and too inflexible.

After the July 26, 1999 County Board Work Session, the ZORC and staff further explored potential zoning ordinance amendment options for maximum lot coverage. In the fall of 2000, the ZORC and staff developed the following three options for an upcoming County Board Work Session.

Option A: Set lot coverage ratio by Zoning Districts. The details of this Option are:

Discussion:

• This option will reduce lot coverage ratio, but probably most lenient option among the three proposed options, and it is unlikely to create a potentially large number of nonconforming lots.
• This option will not prevent construction of larger houses on oversized lots. As mentioned before, many lots in R-5, R-6 and R-8 Districts are larger than the required minimum lot areas. Therefore, this option will be least effective among the three proposed options in controlling large houses on oversized lots.

• This option is likely to allow minor additions to existing houses.
• This option would be the easiest to be understood and be administered among the three options because only one criterion is used to review proposed one-family residential development.

Option B: Set lot coverage ratios by Zoning Districts with caps. The caps used in this option are larger than the caps discussed at the ZORC meeting. To accommodate large number of oversized lots in R-5, R-6, and R-8 Districts, staff raised caps as shown on the table below. The caps discussed at the ZORC meeting were 2,250 square feet, 2,700 square feet, 3200 square feet, 3,500 square feet, and 6,000 square feet respectively for five zoning districts. The details of this Option are as follows.

The following table shows how many square feet of covered areas would be allowed under this option.

Discussion:

• This option will be more effective in reducing lot coverage on oversized lots than Options A or C.
• This option might create some nonconforming lots, particularly on significantly oversized lots in R-5, R-6 and R-8 Districts.
• This option might not restrict minor additions to existing houses on standard sized lots, or closer to the standard sized lots. However, on significantly oversized lots in R-5, R-6 or R-8 Districts, or on significantly undersized lots in R-10 or R-20 Districts, this option will be more restrictive among the proposed three Options.
• This option will permit different sizes of covered areas for the same size lots, depending on in which Zoning District the lot is located.
• This option would be more cumbersome than Option A to apply by citizens and to administer by Zoning Office staff.

Option C: Set lot coverage ratio by lot sizes. Examples are:

Discussion:

• This option is more likely to reduce lot coverage ratio without creating a large number of nonconforming lots than Option B.
• This option will be relatively ineffective in controlling construction of large houses than Option B, if lots are oversized by the applicable zoning district standards. This option will allow construction of larger houses on oversized lots in a controlled manner than Option A would do, because the size of the footprint of a house would be proportional to lot sizes.
• This option is more likely to allow minor additions to existing houses than Option B.
• This option does not conform to the basic concept of the Zoning Ordinance. The Zoning Ordinance regulations are primarily built on "district" based concept. The criteria in this option, however, do not follow any zoning district boundaries.
• One drawback mentioned by ZORC members, concerning this option, is a lack of continuity or substantial jump on permitted covered areas between thresholds. See the examples below.

• This option would be more cumbersome than Option A to administer.

Preliminary Staff Recommendation:

• Staff recommend Option B for the following reasons.

1. This option will reduce lot coverage ratio much more than Options A and C will do, while allowing "average" size houses on standard minimum size lots.
2. This option is most effective among three options in controlling "oversized" houses on oversized lots.
3. This option conforms to the current district-based concept of the Zoning Ordinance.
4. This option might create some nonconforming lots, particularly on oversized lots in R-5, R-6 and R-8 Districts, but revised caps will mitigate these situations.
5. This option would be relatively more cumbersome than Option A to apply by citizens and to administer by Zoning Office staff, but this problem would be in a surmountable level.

• In addition, staff recommends adding a definition of lot coverage to Section 1. Definitions of the Zoning Ordinance.
• Also, staff agrees with the ZORC's recommendation to amend the preamble of the Zoning Ordinance for lot coverage and clarify the intent of lot coverage requirement in the Zoning Ordinance.
  

PRELIMINARY PROPOSAL FOR ZONING ORDINANCE AMENDMENT LANGUAGE:

Section 1. Definitions

Lot Coverage. Determined by dividing that area of a lot occupied by all structures, including covered porches, accessory buildings, off-street parking, and driveways, by the gross area of that lot.

Note: Staff prepared Zoning Ordinance amendment language for Option C. After a Work Session with the County Board, staff will prepare final language for the advertisement of the proposed Zoning Ordinance amendment

Option A.

Section 32. Bulk, Coverage and Placement Requirements

C. Coverage

For the purpose of securing open space for the exclusive use of pedestrians, and/or to provide for light, air circulation, privacy, and landscaped area, except for the lot coverage ratios specified for particular zoning districts, maximum lot coverage ratios shall be established as follows:

a. E except by site plan or use permit approval, no any building or structure in "R," District that are not one-family dwellings, and any building or structure in "RA," and "C-1-O" Districts, including accessory buildings and all areas for parking, driveways, maneuver and loading space, shall cover more than fifty-six (56) percent of the area of the lot, except as may be specified in the various district classifications.

b. Any one-family dwellings in "R" District, including accessory buildings and all areas for parking, driveways, maneuver and loading space, shall be established as follows:

Zoning Districts	R-5	R-6	R-8	R-10	R-20
Lot Coverage Ratios	45%	45%	40%	35%	30%

OPTION B.

Section 32. Bulk, Coverage and Placement Requirements

C. Coverage

For the purpose of securing open space for the exclusive use of pedestrians, and/or to provide for light, air circulation, privacy, and landscaped area, except for the lot coverage ratios specified for particular zoning districts, maximum lot coverage ratios shall be established as follows:

a. E except by site plan or use permit approval, no any building or structure in "R," District that are not one-family dwellings, and any building or structure in "RA," and "C-1-O" Districts, including accessory buildings and all areas for parking, driveways, maneuver and loading space, shall cover more than fifty-six (56) percent of the area of the lot, except as may be specified in the various district classifications.

b. Any one-family dwellings in "R" District, including accessory buildings and all areas for parking, driveways, maneuver and loading space, shall be established as follows:

Option C.

Section 32. Bulk, Coverage and Placement Requirements

C. Coverage

For the purpose of securing open space for the exclusive use of pedestrians, and/or to provide for light, air circulation, privacy, and landscaped area, except for the lot coverage ratios specified for particular zoning districts, maximum lot coverage ratios shall be established as follows:

a. E except by site plan or use permit approval, no any building or structure in "R," District that are not one-family dwellings, and any building or structure in "RA," and "C-1-O" Districts, including accessory buildings and all areas for parking, driveways, maneuver and loading space, shall cover more than fifty-six (56) percent of the area of the lot, except as may be specified in the various district classifications.

b. Any one-family dwellings in "R" District, including accessory buildings and all areas for parking, driveways, maneuver and loading space, shall be established as follows:

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