HomeMy WebLinkAboutCAP 2011-10-10 Item 2B - Discussion - Low Density Residential Zone Development StandardsCity of Tukwila
Jim Haggerton, Mayor
INFORMATIONAL MEMORANDUM
TO: Mayor Haggerton
Community Affairs and Parks Committee
FROM: Jack Pace, Department of Community Development Director
DATE: October 5, 2011
SUBJECT: Low Density Residential Zone Development Standards
ISSUE
Should the City change residential development standards such as height, setbacks or building
footprint to increase the compatibility of infill development with existing structures?
BACKGROUND
This issue was reviewed by the City Council in 2007, when the Council asked staff to review the way
building height was calculated after receiving complaints about a new house that the neighbors felt was
out of scale with the surrounding development. The Community Affairs and Parks Committee reviewed
the issue and asked staff to look at increasing the rear yard setbacks. Based on the research at that
time it was determined that there was no easy fix to regulating the compatibility of infill development
and just increasing the setback would not have prevented the house in question to be built. However it
was decided to review the height issue with an overall look at the single family standards. An overall
look at the policies for residential neighborhoods is usually done as part of the Comprehensive Plan
update. At this time Tukwila is mandated by State Law to update its Comprehensive Plan by 2015. The
resident who raised this issue in 2007 has asked that this issue be revisited. Staff has prepared some
options for the Committee to review in order to address this issue.
DISCUSSION
There are a number of ways that the bulk or the building envelope of a structure can be regulated, such
as building height, lot coverage, setbacks, and in some jurisdictions floor area ratio (FAR). The current
development standards in the LDR zone that regulate single family development are listed in
Attachment A. Also, Attachment B is the comparison of common development standards of the
neighboring jurisdictions. Different development standards that apply to a single family home are
discussed below along with some options for revising the standard in order to address the compatibility
of infill housing with the existing homes.
Building Height
Building height is only one element of the development regulations that controls the bulk or the building
envelope of a structure. At this time the building height is calculated by the method laid out in the
Washington State Building Code. It is measured from the grade plane, which is the average of the
finished ground level adjoining the exterior walls of the structure. On a sloping lot the height of the
structure on one side can be more than the maximum height allowed on a flat lot. Attachment B
discusses the alternate ways of calculating the building height on a sloping lot. One option is to
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establish the grade plane from the lowest ground level around the building. Another option is to allow
the grade plane to be stepped to allow the structures to better respond to the topography of sloping
sites. Either of these options will result in slightly lowering the maximum height of a structure on a
sloping lot. In the case of the house that sparked this discussion changing the building height
measuring point from average grade plane to lowest elevation would have lowered the house by about
five feet. It would not necessarily prevent the construction of a third story.
Setbacks
Increasing the side and rear setback distance for the second and third story of a house would be
another way to reduce the impact of a house on the adjacent properties. The current LDR setbacks are
20' in the front, 10' on the second front (for corner lots), 5' on the sides and 10' in the rear. Tiered side
and rear setbacks that increase by 5' per story would modulate the side elevations of the houses and
reduce their bulk. The increases could have the effect of limiting the development potential of smaller
or oddly shaped lots and preclude the use of stock plans by developers. Another option instead of a
tiered setback is to increase the rear and side yard setbacks for the entire structure and have an even
larger setback for a three story house. Under this option the rear yard setback in LDR for all houses
could be increased to 15 feet and to 25 feet if the house has a third story (with a possible exception for
alley accessed garages or accessory structures). The house that triggered this discussion is set back 5
to 7' from one side, 8' from the other and 65' in the back.
Building Footprint
The LDR zone (TMC 18.10.057) currently limits the footprint of all of the structures on a site to roughly
35% (the percentage decreases as the lot size increases). The building size can be maximized by
building that footprint straight up three stories. For substandard sized lots (under 6,500 sf) there is no
percentage limit, only the required structure setbacks. There have been some concerns expressed with
the formula in the code. Also, there have been some concerns that the formula penalizes development
on larger lots or encourages square footage to be added as another story instead of expansion of the
footprint. One option may be to allow administrative approval to allow variances up to 10% of the
building footprint if certain standards are met such as compatibility in scale with the adjoining homes;
modulation of the fapade; and /or larger than required setbacks are provided.
Floor Area Ratio (FAR)
Tukwila does not currently have FAR standard, which is expressed as the total square footage of the
building(s) divided by the square footage of the lot. This links the size of the building to the size of the
lot regardless of the number of stories. So you can choose to have a larger single story structure or a
taller structure with a smaller footprint. Common single family residential FARs range from .45 to .65,
which would limit a house on a 6,500 sf lot to between 2,925 and 4,225 sf. Tukwila's Comprehensive
Plan suggests a maximum FAR of .5 not including the basement area (CP 7.6.4). The house that
triggered this discussion was on a 13,500 sf lot and had a FAR of .34. One option in lieu of having a
building footprint standard is to have a graduated FAR standard similar to the building footprint
standard, where the percentage decreases as the lot size increases.
CONCLUSION
Tukwila's single family house regulations are similar to those of nearby, similarly situated communities
as seen in the table in Attachment B. The common challenges with infill development are compatibility
of the size /bulk with the existing homes; the street layout and orientation of the homes where not all
homes face the public street; and the architecture /style of the new homes.
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As part of the Comprehensive Plan update the City of Tukwila will review the policies in the residential
neighborhoods chapter. The policies related to neighborhood quality; density requirements; accessory
dwelling units; street layout and sidewalk requirements; orientation of the home; accessory structures
and other broader policies will be reviewed and discussed as part of that process. However if the
Committee decides to review development standards such as building height, setbacks, building
footprint and floor area ratio at this time then staff has laid out some options to consider for further
discussion.
OPTIONS
If the Community Affairs and Parks Committee would like to review the development standards in the
LDR zone then listed below are some options:
1) Change the Zoning Code to require a different method of calculating the building height on
sloping lots;
2) Amend the standards that regulate bulk by:
a) Increasing the rear yard setback in LDR for all houses from 10 to 15 feet and to
25 feet if the house has a third story (with a possible exception for alley accessed
garages or accessory structures); and /or
b) Choose either i) or ii) listed below:
i) Allow administrative approval to allow variances up to 10% of the building
footprint standard if certain standards are met such as compatibility in
scale with the adjoining homes; modulation of the fagade; and /or larger
than required setbacks are provided; or
ii) Adopt a graduated FAR standard similar to the building footprint standard,
where the percentage decreases as the lot size increases.
3) No Action.
RECOMMENDATION
The options listed above under #1 and #2 will result in slightly reducing the size and the bulk of the
homes that could be built in Tukwila. However none of the changes to the building standards would
make a significant difference in the bulk of the house that was the source of the neighborhood
complaint. Staff recommends that at a minimum the method of calculating building height on sloping
lots be revised. If the Committee wishes to look at options 1 and 2, staff recommends that this item be
forwarded to the Planning Commission for further review. Staff would bring back the Planning
Commission's recommendation to the City Council for final action.
ATTACHMENTS
Attachment A: Tukwila's Single Family Development Standards
Attachment B: Comparison of development standards of the neighboring jurisdictions
Attachment C: Methods of calculating building height
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Attachment A
Development Standards in the Low Density Residential (LDR) Zone
Minimum lot size 6500 sq. ft.
Average Lot Width (minimum) 50 feet
Setbacks:
Front 120 feet
Front, decks or porches 15 feet
Second Front 10 feet
Sides 5 feet
Rear 10 feet
Height 30 feet maximum and is measured per
Washington State Building Code (from the
average grade plane to the mid -point of the
highest roof)
Parking Two spaces for each dwelling unit up to 3
bedrooms and then one additional space for
every two bedrooms in excess of 3 bedrooms
in a dwelling unit.
In addition to the standards listed above the following sections regulate accessory dwelling
units, building footprint and the design of the dwelling units:
18.10.030 Accessory dwelling units
Accessory dwelling units are permitted in LDR zone, provided the following criteria are met:
a. minimum lot of 7,200 square feet;
b. accessory dwelling unit is no more than 33% of the square footage of the primary residence and a maximum
of 1,000 square feet, whichever is less;
c. one of the residences is the primary residence of a person who owns at least 50% of the property,
d. dwelling unit is incorporated into the primary detached single family residence, not a separate unit, so that
both units appear to be of the same design as if constructed at the same time;
e. minimum of three parking spaces on the property with units less than 600 square feet, and a minimum of
four spaces for units over 600 square feet; and
f. the units are not sold as condominiums.
18.10.057 Maximum Building Footprint
The maximum total footprint of all residential structures located on a lot in the Low Density Residential District shall
be limited to 35% of the lot area, provided:
1. The maximum footprint is reduced by 0.125% for each 100 square feet of lot area in excess of 6,500 square feet
and less than 19,000 square feet;
2. The maximum footprint shall be 4,000 square feet for lots between 19,000 square feet and 32,670 square feet;
3. The maximum footprint shall be 5,000 square feet for lots between 32,760 square feet and 43,560 square feet;
4. The maximum footprint shall be 6,000 square feet for lots over 43,560 square feet; and
5. For lots less than 6,500 square feet in size, the maximum total footprint shall be the area defined by the application
of the standard setback requirements set forth in the applicable Basic Development Standards, up to a maximum
of 2,275square feet.
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Attachment A
18.50.050 Single Family Dwelling Design Standards
All new single family dwellings, except those that are part of an approved Housing Options Demonstration Program,
constructed under building permits submitted to the City after August 19, 2005, must:
1. be set upon a permanent foundation, with the space from the bottom of the home to the ground enclosed by
concrete or an approved concrete product that can be either load bearing or decorative;
2. if a manufactured home, be comprised of at least two fully enclosed parallel sections, each of not less than 12
feet wide by 36 feet long;
3. be thermally equivalent to the State's energy code;
4. have exterior siding that is residential in appearance including, but not limited to, wood clapboards, shingles or
shakes, brick, conventional vinyl siding, fiber cement siding, wood composite panels, aluminum siding or similar
materials. Materials such as smooth, ribbed or corrugated metal or plastic panels are not acceptable;
5. have the front door facing the front or second front yard, if the lot is at least 40 feet wide; and
6. have a roofing material that is residential in appearance including, but not limited to, wood shakes or shingles,
standing seam metal, asphalt composition shingles or tile, with a minimum roof pitch of 5:12.
18.50.055 Single Family Design Standard Exceptions
The design standards required at 18.50.050 (5) and (6) may be modified by the DCD Director as a Type 2 Special
Permission decision.
1. The criteria for approval of a roof pitch flatter than 5:12 are as follows:
a. The proposed roof pitch is consistent with the style of the house (for example modern, southwestern);
b. If a flat roof is proposed, the top of the parapet may not exceed 25 feet in height;
c. If a sloped roof is proposed, it must have at least 24 -inch eaves; and
d. The house exhibits a high degree of design quality, including a mix of exterior materials, detailing, articulation
and modulation.
2. The criteria for approval of a house with a front door that faces the side or rear yard are as follows:
a. The topography of the lot is such that pedestrian access is safer or more convenient from the side or rear
yard;
b. The house will be set back at least twice the minimum front yard setback;
c. The entrance is oriented to take advantage of a site condition such as a significant view; or
d. The entry feature is integral to a unique architectural design.
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Attachment B
Below is a table listing single family development standards in nearby jurisdictions
Building Envelope
1 7 w
vT t
41 1 1 ��s y
t 8Cy L
Rear 10'
Impervious
Surface
Kent
Jurisdiction
Standard
Tukwila
stry /35'
30' to roof
Max. Height
mid -point
Min. Lot
60', 70' 50', 60'
Area
6,500
Lot Width
50'
15', 20'
35%(2,275)
10'
at 6,500 sf,
garage 20'
setbacks
only limit
Max. Lot
below 6,500
Coverage
sf
Setbacks:
20'
Front
20'
Second
Front
10'
Side
5'
Rear 10'
Impervious
Surface
Kent
Renton
2.5
stry /35'
2 stry /35' 2 stry /30'
7,600
8,000 4,500
45%
60', 70' 50', 60'
50'
Corner Corner
SeaTac Burien
30' 35'
5,000 to
15,000 7,200
50'
5' 25' 20' 15' 5'
70%
60%
Seattle
30' 5' for
roof
5,000
None
35% or
1,000+
15%
(1,750) for
lots under
5,000 sf
20'
10'
5'
Smaller of
25' or 20%
lot depth
Greater
Greater
of 2,500sf
of 2,500sf
45%
or 35%
or 35% 35%
35%
15', 20'
10'
30'
garage 20'
20'
15', 20'
10'
20'
garage
20'
15' Total,
5'
5' min.
5' 5'
5'
5' 25' 20' 15' 5'
70%
60%
Seattle
30' 5' for
roof
5,000
None
35% or
1,000+
15%
(1,750) for
lots under
5,000 sf
20'
10'
5'
Smaller of
25' or 20%
lot depth
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Attachment C
Methods of Calculating Building Height
Building Height is defined in the Zoning Code (TMC 18.06. 100) as:
"Building height" means the height of a building as calculated by the method in the Washington
State Building Code.
The Washington State Building Code defines Building Height and the Grade Plane as:
Building Height: The vertical distance from grade plane to the average height of the highest
roof surface.
Grade Plane: A reference plane representing the average of the finished ground level adjoining
the building at all exterior walls. Where the finished ground level slopes away from the exterior
walls, the reference plane shall be established by the lowest points within the area between the
building and the lot line or, where the lot line is more than 6 ft (1829 mm) from the building
between the structure and a point 6 ft (1829 mm) from the building.
Height Limit
s Actual Grade
Average Grade
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Attachment C
In case of a sloping lot the height is measured from the average grade plane and the visual impact
of a structure can be different if it was on a flat lot. This is particularly of importance in
residential zones where the compatibility of existing and new homes becomes an issue. In order
to address sloping lots the City Council has options to amend the building height definition as
follows:
"Building height" means the height of a building as calculated by the method in the Washington
State Building Code, except if the slope of the subject property is 15% or more and the subject
property is zoned residential then building height shall be calculated by either option a) or option
b) listed below:
a) The grade plane shall be established from the lowest finished grade or lowest existing
grade (whichever is lower) adjoining the building at any exterior wall; or
Height Limit
Actual Grade is
greater than
15%
Lov est Grade
it
Attachment C
b) In order to allow the structures to better respond to the topography of sloping sites a
structure will be allowed to adjust the points at which height is measured. This may be
accomplished by establishing separate grade planes at intervals of least 15 feet for
different sections of the structure.
HeightLimit
X 15'
15' Section 3
1 S'
r Section 2
Section 1
El
0
Average Grade or Lowest Grade f o r e ach section
0
Additionally, the city may require a topographic survey from a licensed land surveyor when the
existing grade will be disturbed to accomplish the construction or when the final height of the
new structure in the area where grade is being disturbed is within 2 feet of the allowed height
limit for the structure as measured above the existing or finished grade.
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