Low/Moderate Density Residential

This subject area will deal with issues relating to lower density residential neighborhoods.  Areas that would fit into the traditional R-1 through R-4 zones with largely single family and two-family housing stock are the focus.  This group will look at a very wide variety of issues including alley lots, accessory dwellings, corner retail stores, related non-residential uses, bulk and setback requirements, and many others.  This group will also be examining the existing residential zoning categories and overlays to determine if these are sufficient to meet the needs of the city's neighborhoods.

Working Group
This working group met on the following dates:

March 24, 2008
March 31, 2008
April 21, 2008
May 7, 2008
May 14, 2008
May 21, 2008
June 4, 2008
June 11, 2008
June 26, 2008

UPDATE: A final meeting of the Working Group will be held on November 19, 2008 to discuss updates and changes to the preliminary recommendations before going to the Task Force meeting in December. The meeting will be held at 441 4th St. NW, 11th Floor.

To sign up for notification or to participate in this group click here.

Questions? Click here. 

Low to Moderate Building Study: Preliminary Results

As part of the overall study of Low and Moderate Density Residential areas, the Office of Planning conducted an empirical study of residential buildings and lots in the District of Columbia. The purpose of the study was to gather information that would aid in the selection and application of tools to regulate future development in the District.

The Data Information Outline and Building Study Documents section includes:

• A Power Point presentation which provides a summary of the information, analysis of the data and key conclusions;
  
  Direct Link to Mtg. 7 Presentation Slides
  Direct Link to Mtg. 7 Presentation Outline Notes
   

• Background information related to the preparation of the study, including the sampling methodology and the data collected;
  
  Direct Link to Building Study Methodology

• A map of the sampled properties; and
  
  Sampled Lots Map

• Summary tables of the data.

It is recommended that the PowerPoint presentation be reviewed first in order to understand the context for the information collected and its intended purpose. In addition, the background information related to the preparation of the study is helpful in understanding how the representative lots were identified, what information was collected, how it was collected, and why it was collected.

The Data Information Outline identifies the documents posted, provides a summary of the information contained within each document, and provides  hyperlinks to view the documents. Further information regarding the data and its collection is available upon request, by directly contacting the Development Review Division. Please forward any questions or requests to:

Michael Giulioni

Development Review Specialist, Development Review

Office of Planning, District of Columbia

801 N. Capitol St. NE, Suite 3000

Washington DC, 20002

PH: 202-442-8813

michael.giulioni@dc.gov

Lastly: the results of this study are to be considered preliminary in nature. The results of the study have been useful in identifying general trends, upon which the Office of Planning’s preliminary recommendations were based. More research is essential to establishing firm standards. This study and the associated discussion will provide important direction for future work planning.

Building Study Data Information Outline:

Introduction:

The building study data includes a wide variety of measurements from the lots sampled in the study. For ease of reference the information has been categorized into different packages based on the building typology. The presentation of the data in these packages allows users to analyze each measure gathered in relation to the building type, both within the different zones and relative to the entire population. Additional data summary packages are also provided to enable macro-level or city-wide analysis.

It is important to note that as the data in the overall sample set are segmented into different categories (by zone and building type) the sample sizes become smaller. This is a key deficiency of the data set, and puts limitations on the conclusions that can be drawn for the smaller subsets of data.. Further detail regarding each data package and associated summary tables is provided below.

Lastly, data has been collected regarding certain subject matter that has yet to be distilled into a presentation format (e.g., information on accessory buildings and information regarding building types with a density of two units or more per lot).   Due to time considerations and the quantity of data available, there have been limitations on the amount of information that could be presented at this time. 

Lot Data Summary Package:

The Lot Data Summary Package provides five summary tables with information regarding two main areas. The first three tables (LD-1 through LD-3) provide a comparison of lots based on the different types that were identified.    The remaining two tables (LD-4 and LD-5) provide a comparison of non-conforming lots to conforming lots with respect to the minimum lot area and the minimum lot width standards of the current zoning regulations.

The comparisons based on lot type include:

• An analysis of regular lots (those that fit the general shape of a rectangle or square) and irregular lots (all other lots).
• A breakdown of all the irregular lots in relation to the proportion they represented of the total sample. Three main lot types are identified, as well as an ‘other’ category (generally, any lot with roughly parallel lot lines).
• A comparison of corner lots vs. interior lots.

These comparisons are intended to develop an understanding of the potential need for standards that adequately regulate irregular lots within the zoning review process.

Direct Link to Lot Data Summary Package

Unit Data Summary Package:

The Unit Data Summary Package provides information in three main areas. The first set of three tables provides some aggregate analysis regarding building types and the associated number of units located within them.   The first table provides a breakdown of the distribution of the overall number of lots relative to building type and the number of dwelling units relative to the lot. The remaining two tables provide the average unit size and the average building size associated with a particular unit to lot ratio and building type. The numbers represented are ‘gross’ in nature and include building area that is considered common space outside of units (e.g.: hallways and service space). 

The second set of tables (Tables UD-5 through UD-11) provides an overview of lots in the sample, stratified by the number of units per lot. Each table is based first upon the unit to lot ratio. Each table is then further broken down by zone district and building type. All percentages in these tables are based on the total number of sampled lots in relation to the population identified in UD - 4. 

The final table provides an extrapolation of the number and relative proportion of units based on the unit to lot ratio, building type and the average number of units per building based on the defined classifications. The proportional distribution is presented relative to the overall number of units extrapolated.   These distributions are based on the total number of lots extrapolated in each unit to lot ratio table (UD-5 through UD-11).  The total number of lots has been identified and then multiplied by the number of units per lot to determine the relative proportion of units based on building type and density.

This table is intended to provide information regarding the estimated distribution of units based on the types of buildings (single unit vs. multi-unit) in low to moderate density residential areas.

Direct Link to Unit Data Summary Package

Porch and Roof Data Summary Package:

The Porch and Roof Data Summary Package provides information on two main areas: the number of sampled buildings that have a porch, and a breakdown of the distribution of roof types by both zone district and building type.

The Porch Summary Table shows, broken down by building type and zone district, the number of buildings in each category that have porches. Each number is also reported as a percentage of the total sample of buildings. The final two columns in this table sum the results across all zone districts for each building type, to arrive at citywide totals. .   The Roof Type Summary Table – City Wide and by Zoning Category represents the data related to roof type in the same manner.   The Roof Type Summary Table provides the distribution of buildings based on both the type of roof and the building type relative to the overall sample.

Direct Link to Porch and Roof Data Summary Package

Data Summary Packages by Building Type for Single Household Buildings:

The Data Summary Packages are divided into three packages based on the three main building types. These packages include only data for lots with a single dwelling unit .   Within each package, data is presented in individual tables based on the specific measure that was recorded (e.g., lot area). Each package consists of 18 tables, with each table reporting data collected on a single measure (e.g., lot area). Each table presents the average of the measure, the standard deviation, (the measurement of the variety of the data relative to the average) and the sample counts upon which the average and standard deviation are based. The lowest and highest values for each measure are presented.  Data is presented for the city as a whole, and broken down by zone districts.  For futher information regarding standard deviation the following overview is recommended: http://en.wikipedia.org/wiki/Standard_deviation

The data summary packages for each building type are divided into two sections. The first section in each package consists of tables which report “non-lot relative” data. The second section reports “lot relative” data. Non-lot relative measures are those that are unrelated to the shape of the lot, whereas those that are relative measures are directly related to the shape of the lot. The lot relative measures have been filtered to remove irregular lots that would result in more irregularity to the data. The non-lot relative measures present the full sample without filtering.  

 
Direct Link to Detached - Single Household - Data Summary Package

Direct Link to Semi-Detached - Single Household - Data Summary Package

Direct Link to Row - Single Household - Data Summary Package

 
Measurement Standards Comparison Charts Package:

The Measurement Standards Correlation Charts Package provides scatter plots that display the relative correlation of different measures to one another. 

Three charts are presented for each building type: 

•  the building’s footprint is compared to its coverage;
• the building’s Floor Area Ratio is compared to its Gross Floor Area (GFA); and
• the lot area is compared to the building’s Gross Floor Area. 

The intent of these charts is to establish whether there is a direct relationship between each of these pairs of variables. The charts suggest that there is a correlation between the area of a lot and its building’s GFA, but little or no correlation between the other pairs of variables.

Direct Link to Measurement Standards Comparison Charts Package