HomeMy WebLinkAboutCAP 2007-04-24 Item 2A - Code Amendment - Low Density Residential (LDR) Building Height
City of Tukwila
Steven M. Mullet, Mayor
Department of Community Development
Steve Lancaster, Director
INFORMATION MEMORANDUl\1
To:
Mayor Mullet
Community Affairs and Parks 1~ttee
Jack Pace, Acting DCD Director ~\
April 18, 2007
Code Amendment - LDR Building Height
FROM:
DATE:
SUBJECT:
ISSUE
Should the City change the way building heights are regulated to limit the bulk of new houses?
BACKGROUND
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. Currently the LDR zone allows buildings up to 30 feet in height measured
according to the method in the \Vashington State Building Code (IBC 2003) from the average
ground surface to the midpoint of a pitched roof. At their March 15th meeting the CAP reviewed
a diagram showing how various jurisdictions calculated building height and how that affected the
building envelope.
There was some support for following Kent's approach which is a 35' height limit from "the
lowest point within five feet of the foundation." Some codes specify that the point of
measurement must be from "undisturbed ground". The Kent approach would have the effect of
reducing the allowable height of buildings on slopes by a few feet depending on the steepness of
the slope and whether retaining walls were used to alter the surrounding grades but raising the
height of buildings on flat ground ifthe height limit was changed to 35'.
AL TERNA TIVES/DISCDSSION/ANAL YSIS
Building height is only one element of the zoning regulations that control the bulk or building
envelope of a structure. The others are lot coverage, setbacks and in some jurisdictions floor area
ratio (FAR). Simply lowering building height or changing the way it is calculated may not result
in new buildings that are significantly more compatible with existing development patterns. In
the case of the house that sparked this discussion changing the building height measuring point
from average grade plane to lowest elevation within 5' would only have lowered the house by
about 5 feet and not reduced the bulk. Other ideas would be to control the bulk of houses
through aFAR or use tiered setbacks such as those in the multi-family zones.
NO
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6300 Southcenter Boulevard, Suite #100 · Tukwila, Washington 98188 · Phone: 206-431-3670 · Fax: 206-431-3665
Building Envelope
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Below is a table listing single family development standards in nearby jurisdictions:
Jurisdiction
Standard Tukwila Kent Renton SeaTac Burien
2.5
Height 30' sty/35' 2 sty/35' 2 stry/30' 30' 35'
5,000 to
Lot Area 6,500 7,600 8,000 4,500 15,000 7,200
60', 70' 50', 60'
Lot Width 50' 50' Corner Corner 50'
Greater Greater
Lot 35% at of 2,500sf of 2,500sf
Coverage 6,500 sf 45% or 35% or 35% 35% 35%
Setbacks: 15', 20'
Front 20' 10' 30' garage 20' 20'
Second 15', 20'
Front 10' 10' 20' garage 20'
15' Total,
Side 5' 5' 5' min. 5' 5' 5'
Rear 10' 5' 25' 20' 15' 5'
Impervious
Surface 60% 70%
Lot Coverage
The LDR zone currently limits the lot coverage (footprint) of all of the structures on a site to
roughly 35% (the percentage decreases as the lot size increases) TMC 18.10.057. This
percentage is common among jurisdictions that use this regulation, see table above. However the
building size can be maximized by building that footprint straight up three stories.
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Floor Area Ratio
FARis 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. Common single family residential F ARs range from .45 to .65 which would limit a
house on a 6,500 sflot to between 2,925 and 4,225 sf. The house that triggered this discussion
was on a 13,500 sflot and had a FAR of.34.
Floor Area Ratio (FAR)
1:1 Ratio
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Setbacks
Increasing the side and rear setback distance for the second and third stories 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, 5' on the sides and 10' in the rear. Tiered
side and rear setbacks that increased by 5' per story for lots that are at least 50' wide 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. The house that triggered this discussion is set back 5 to 7' from
one side, 8' from the other and 65' in the back.
RECOl\1MENDATION
Tukwila's single family house regulations are similar to those of nearby, similarly situated
communities as seen in the table above. If the Council wished to modify them staff could
develop recommended changes in one or more ofthe following areas:
1) Change the defInition of building height (this would affect development throughout the
City);
2) Reduce the allowed building height in LDR;
3) Reduce the lot coverage standard in LDR;
4) Replace the lot coverage standard with a FAR limitation in LDR;
5) Require tiered side and rear setbacks in LDR.
None of these changes would have made a signifIcant difference in the bulk of the house that was
the source ofthe neighborhood complaint. No action is recommended by staff.
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