HomeMy WebLinkAboutE - King County Density Worksheet.pdf S27 Web date: 11/26/2012
SubdivDensityDimensionCalcFORM-doc.doc lc-cal-subden.pdf S27 111/26/2012 Page 1 of 6
Department of Permitting
and Environmental Review
35030 SE Douglas Street, Suite 210
Snoqualmie, WA 98065-9266
206-296-6600 TTY Relay: 711
www.kingcounty.gov
Preliminary Subdivision Worksheet Relating to Density and Dimensions
Several development regulations play a role in the creation of a subdivision within King County. Determining
the allowable density, minimum density, and a lot width on a piece of property can be confusing. This
worksheet will assist you in correctly applying specific portions of the code and will be used to determine if a
proposed subdivision or short subdivision meets the density and dimensions provisions of the King County
Zoning Code (Title 21A). This worksheet is designed to assist applicants and does not replace compliance with
adopted local, state and federal laws.
Pre-application conferences are required prior to submittal of a subdivision or short subdivision. These
conferences help to clarify issues and answer questions. They may save you both time and money by
eliminating delays resulting from requests for additional information and revisions. You may call 206-296-6600
to find out how to arrange for a pre-application conference.
Worksheet Prepared By: Wayne Potter, Barghausen Consulting Engineers, Inc. Date: 9-13-2016
(Print Name)
Subdivision Name: Canyon Terrace
Comprehensive Plan Land Use Designation: Urban Residential - 6-12 DU Per Acre
Zoning: R-6
If more than one Comprehensive Plan Land Use designation or zone classification exists for the property, show
the boundary between the land uses or zones and the area within each on the preliminary plat map. If a single
lot is divided by a zone boundary, transferring density across zones on that lot may be permitted subject to the
provisions of King County Code (KCC) 21A.12.200.
PLEASE COMPLETE ONLY THE APPLICABLE PORTIONS OF THIS FORM
I. Site Area (KCC 21A.06.1172) also see (KCC 21A.12.080):
Site area (in square feet) is the TOTAL horizontal area of the project site.
Subdivision Density and
Dimension Calculations
_______________________________
File Number
(To be filled in by Permitting Staff)
For alternate formats, call 206-296-6600.
CITY OF RENTON FILE NO:
LUA13-000840PLAT OF CANYON
TERRACE
DATE: 9-13-2016
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Calculation:
574,768.9 sf Gross horizontal area of the project site
574,768.9 sf Site area in square feet
NOTE: To continue calculations, convert site area in square feet to acres by
dividing by 43,560
13.19 acres Site area in acres
NOTE: When calculating the site area for parcels in the RA Zone, if the site
area should result in a fraction of an acre, the following shall apply:
Fractions of .50 or above shall be rounded up to the next whole
number and fractions below .50 shall be rounded down. Example: If
the site area in acres is 19.5 acres (less the submerged land and
less the area that is required to be dedicated on the perimeter of a
project site for public right-of-way) the site area can be rounded up to
20 acres. No further rounding is allowed. (See KCC 21A.12.080)
II. Base Density (KCC 21A.12.030 - .040 tables):
The base density is determined by the zone designations(s) for the lot.
6 du/acre
III. Allowable Dwelling Units and Rounding (KCC 21A.12.070):
The base number of dwelling units is calculated by multiplying the site area by the base density in dwelling
units per acre (from KCC 21A.12.030 - .040 tables).
13.19 site area in acres (see Section 1.) X 6 base density (see Section II)
= 79 allowable dwelling units
Except as noted below, when calculations result in a fraction, the fraction is rounded to the nearest whole
number as follows:
A. Fractions of .50 or above shall be rounded up; and
B. Fractions below .50 shall be rounded down.
NOTE: For parcels in the RA Zone, no rounding is allowed when calculating the allowable number of dwelling
units. For example, if the calculation of the number of dwelling units equaled 2.75, the result would be 2
dwelling units. Rounding up to 3 is not allowed. (See KCC 21A.12.070(E).)
IV. Required On-site Recreation Space (KCC 21A.14.180):
This section must be completed only if the proposal is a residential development if more than four dwelling
units in the UR and R zones, stand-alone townhouses in the NB zone on property designated Commercial
Outside of Center if more than four units, or any mixed use development if more than four units. Recreation
space must be computed by multiplying the recreation space requirement per unit type by the proposed
number of such dwelling units (KCC 21A.14.180). Note: King County has the discretion to accept a fee in lieu
of all or a portion of the required recreation space per KCC 21A.14.185.
Apartments and town houses developed at a density greater than eight units per acre, and mixed use must
provide recreational space as follows:
90 square feet X proposed number of studio and one bedroom units
170 square feet X proposed number of two bedroom units +
170 square feet X proposed number of three or more bedroom units +
Recreation space requirement =
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Required On-site Recreation Space Continued
Residential subdivisions, townhouses and apartments developed at a density of eight units or less per acre
must provide recreational space as follows:
390 square feet X proposed number of units =
Mobile home parks shall provide recreational space as follows:
260 square feet X proposed number of units =
V. Net Buildable Area (KCC 21A.06.797):
This section is used for computing minimum density and must be completed only if the site is located in the R-4
through R-48 zones and designated Urban by the King County Comprehensive Plan. The net buildable area is
the site area (see Section I) less the following areas:
0 areas within a project site which are required to be dedicated for public rights-of-way in
excess of sixty (60') of width
+ 32,134 sf critical areas and their buffers, to the extent they are required by King County to
remain undeveloped
+ 26,512 sf areas required for above ground stormwater control facilities including, but not limited to,
retention/detention ponds, biofiltration swales and setbacks from such ponds and swales
+ 54,230 sf areas required by King County to be dedicated or reserved as on-site recreation areas.
Deduct area within stormwater control facility if requesting recreation space credit as allowed by KCC
21A.14.180 (see Section IV)
+ 0 regional utility corridors, and
+ 0 other areas, excluding setbacks, required by King County to remain undeveloped
= 112,876 sf Total reductions
Calculation:
574,768.9 sf site area in square feet (see Section1)
– 112,876 sf Total reductions
= 461,892.9 sf Net buildable area in square feet NOTE: convert site area is square feet to
acres by dividing by 43,560
= 10.60 acres Net buildable area in acres
VI. Minimum Urban Residential Density (KCC 21A.12.060):
The minimum density requirement applies only to the R-4 through R-48 zones. Minimum density is determined
by multiplying the base density in dwelling units per acre (see Section II) by the net buildable area of the site in
acres (see Section V) and then multiplying the resulting product by the minimum density percentage from the
KCC 21A.12.030 table. The minimum density requirements may be phased or waived by King County in
certain cases. (See KCC 21A.12.060.) Also, the minimum density requirement does not apply to properties
zoned R-4 located within the rural town of Fall City. (See KCC 21A.12.030(B)12.)
Calculation:
6 base density in du/ac (see Section II) X 10.60 acres Net buildable area in acres (see Section V)
= 85% X minimum density % set forth in KCC 21A.12.030 or as adjusted in Section VII
= 54 minimum dwelling units required
72 28,080 sf
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VII. Minimum Density Adjustments for Moderate Slopes (KCC 21A.12.087):
Residential developments in the R-4, R-6 and R-8 zones may modify the minimum density factor in KCC
21A.12.030 based on the weighted average slope of the net buildable area of the site (see Section V). To
determine the weighted average slope, a topographic survey is required to calculate the net buildable area(s)
within each of the following slope increments and then multiplying the number of square feet in each slope
increment by the median slope value of each slope increment as follows:
sq. ft 0-5% slope increment X 2.5% median slope value =
+ sq. ft 5-10% slope increment X 7.5% median slope value = +
+ sq. ft 10-15% slope increment X 12.5% median slope value = +
+ sq. ft 15-20% slope increment X 17.5% median slope value = +
+ sq. ft 20-25% slope increment X 22.5% median slope value = +
+ sq. ft 25-30% slope increment X 27.5% median slope value = +
+ sq. ft 30-35% slope increment X 32.5% median slope value = +
+ sq. ft 35-40% slope increment X 37.5% median slope value = +
Total square feet Total square feet
in net buildable area adjusted for slope
Calculation:
total square feet adjusted for slope divided by total square feet in net buildable area
= weighted average slope of net buildable area
= % (Note: multiply by 100 to convert to percent – round up to nearest whole percent)
Use the table below to determine the minimum density factor. This density is substituted for the minimum density
factor in KCC 21A.12.030 table when calculating the minimum density as shown in Section VI of this worksheet.
Weighted Average Slope of Net
Buildable Area(s) of Site:
Minimum Density Factor
0% -- less than 5% 85%
5% -- less than 15% 83%, less 1.5% each 1% of
average slope in excess of 5%
15% -- less than 40% 66%, less 2.0% for each 1% of
average slope in excess of 15%
EXAMPLE CALCULATION FOR MINIMUM DENSITY ADJUSTMENTS FOR MODERATE SLOPES:
sq. ft 0-5% slope increment X 2.5% median slope value =
+ 10,000 sq. ft 5-10% slope increment X 7.5% median slope value = 750 +
+ 20,000 sq. ft 10-15% slope increment X 12.5% median slope value = 2,500 +
+ sq. ft 15-20% slope increment X 17.5% median slope value = +
+ sq. ft 20-25% slope increment X 22.5% median slope value = +
+ sq. ft 25-30% slope increment X 27.5% median slope value = +
+ sq. ft 30-35% slope increment X 32.5% median slope value = +
+ sq. ft. 35-40% slope increment X 37.5 % median slope value = +
30,000 Total square feet 3,250 Total square feet
in net buildable area adjusted for slope
3,250 Total square feet adjusted for slope divided by 30,000 Total square feet in net buildable area
= .108333 Weighted average slope of net buildable area
= 11% (Note: multiply by 100 to convert to percent – round up to nearest whole percent)
Using the table above, an 11% weighted average slope of net buildable area falls within the 5% -- less than 15%
range which has a minimum density factor of 83%, less 1.5% for each 1% of average slope in excess of 5%. Since
11% is 6% above 5%, multiply 6 times 1.5 which would equal 9%. Subtract 9% from 83% for an adjusted minimum
density factor of 74%. This replaces the minimum density factor in KCC 21A.12.030 table. - NOT
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VIII. Maximum Dwelling Units Allowed (KCC 21A.12.030 - .040):
This section should be completed only if the proposal includes application of residential density incentives
(KCC 21A.34) or transfer of density rights (KCC 21A.37). Maximum density is calculated by adding the bonus
or transfer units authorized to the base units calculated in Section III of this worksheet. The maximum density
permitted through residential density incentives is 150 percent of the base density (see Section II) of the
underlying zoning of the development or 200 percent of the base density for proposals with 100 percent
affordable units. The maximum density permitted through transfer of density rights is 150 percent of the base
density (see Section II) of the underlying zoning of the development.
base density in dwelling units per acre see (Section II) X 150% = maximum density
maximum density in dwelling units per acre X site area in acres =
maximum dwelling units allowed utilizing density incentives (KCC 21A.34)
base density in dwelling units per acre (see Section II) X 200% = maximum density
maximum density in dwelling units per acre X site area in acres =
maximum dwelling units allowed utilizing density incentives with 100 percent affordable units (KCC 21A.34)
base density in dwelling units per acre (see Section II) X 150% = maximum density
maximum density in dwelling units per acre X site area in acres =
maximum dwelling units allowed utilizing density transfers (KCC 21A.37)
Calculation:
base allowable dwelling units calculated in Section III
+ bonus units authorized by KCC 21A.34
+ transfer units authorized by KCC 21A.37
total dwelling units (cannot exceed maximum calculated above)
IX. Minimum Lot Area For Construction (KCC 21A.12.100):
Except as provided for non-conformances in KCC 21A.32:
A. In the UR and R zones, no construction shall be permitted on a lot that contains an area of less than
2,500 square feet or that does not comply with the applicable minimum lot width, except for townhouse
developments, zero-lot-line subdivisions, or lots created prior to February 2, 1995, in a recorded
subdivision or short subdivision which complied with applicable laws, and;
B. In the A, F, or RA Zones:
1. Construction shall not be permitted on a lot containing less than 5,000 square feet; and
2. Construction shall be limited to one dwelling unit and residential accessory uses for lots containing
greater than 5,000 square feet, but less than 12,500 square feet. (KCC 21A.12.100)
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X. Lot Width (KCC 21A.12.050(B)):
Lot widths shall be measured by scaling a circle of the applicable diameter within the boundaries of the lot as
shown below, provided than an access easement shall not be included within the circle. (See KCC
21A.12.050).
Check out the Permitting Web site at www.kingcounty.gov/permits
Lot Width Circle
30 Feet
Lot Width Measurement