Seattle SDCI Tip #220 - Lot Coverage, Height, Yard, and Garage Standards for Homes in Neighborhood Residential Zones

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Seattle, WA 98124-4019

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220

Lot Coverage, Height, Yard,

and Garage Standards for

Homes in Neighborhood

Residential Zones

Updated June 12, 2023

Seattle has three zones in which single family homes are

the predominant type of development: NR3, NR2 and

NR1. The abbreviation “NR” stands for Neighborhood

Residential, and the numbers following the abbreviation

indicates the minimum lot area generally needed to build

a home in that zone.

Other than the differing lot size

requirements, Land Use Code standards that regulate

the size and location of buildings are the same for all

neighborhood residential zones. Development in Neigh-

borhood Residential Small Lot (RSL) zones is subject to

different standards and is beyond the scope of this Tip.

New buildings and modifications to existing homes must

conform to the lot coverage, height and yard standards

described in the Land Use Code. Some examples of,

and exceptions to, the requirements are presented here;

however, you should also review the sections of the

code that might apply to your project before prepar-

ing plans for a permit application. Code references are

included in this Tip for convenience.

In addition to reading this pamphlet and the Land Use

Code, you are welcome to discuss your project with a

planner through the SDCI Applicant Services Center,

www.seattle.gov/sdci/about-us/who-we-are/appli-

cant-services-center or (206) 684-8850.

Some existing lots are smaller than the minimum size, and the code

allows creation of small lots under certain conditions - see Section

23.44.010 of the Land Use Code, which is found in Title 23 of the

Seattle Municipal Code (SMC). The section references used in this

bulletin all begin with the chapter number (23), followed by the section

number (.44) and the subsection (.020).

LOT COVERAGE

Homes (principal structures) and associated struc-

tures (accessory structures) may cover 35 percent of

the lot on lots 5,000 square feet or greater in area. On

lots less than 5,000 square feet in area, these struc-

tures may cover 1,000 square feet plus 15 percent of

the lot (23.44.010C). When calculating lot coverage,

it is important to note that distinct portions or areas

of a lot that have dimensions less than 10 feet will be

excluded when calculating the overall lot area for the

purpose of determining lot coverage.

This calculation is made on the footprint of all structures

on the entire lot. Balconies, bay windows, and architec-

tural projections must be included in calculating the foot-

print even though they do not actually touch the ground.

However, the first 36 inches of eaves and gutters are

exempted from this calculation.

Accessory structures and permitted portions of

principal structures may cover no more than 40

percent of the required rear yard (23.44.016E).

Detached ADUs may cover up to an additional 20

percent (up to 60 percent) of a required rear yard

as long as no exceptional trees or trees over 2 feet

in diameter measured 4.5 feet above the ground

are removed.

Lot Coverage Exceptions (23.44.010D)

If any of your lot lines abut a dedicated alley, you may

add half the area of the alley to your total lot area, up to

a maximum of 10 percent of your lot area, when com-

puting lot coverage.

Certain structures are not counted in lot coverage.

These include:

n Pedestrian access bridges that are 5 feet wide or

less (uncovered and unenclosed).

n Barrier-free access ramps or other access for the dis-

abled or elderly meeting Washington State Building

Code Chapter 11.

n Decks or parts of decks which are not over 36 inches

above the existing grade.

SDCI Tip #220—Lot Coverage, Height, Yard & Garage Standards for Homes in Neighborhood Residential Zones

page 2

LEGAL DISCLAIMER: This Tip should not be used as a substitute for codes and regulations. The applicant is responsible for compliance

with all code and rule requirements, whether or not described in this Tip.

n Freestanding structures such as fences, bulkheads

and freestanding walls, but not arbors.

n Underground structures or the underground portion

of a structure.

n The first 36 inches of eaves and gutters projecting

from principal or accessory structures.

n Solar collectors meeting the provisions of 23.44.046 and

swimming pools meeting the provisions of 23.44.044.

Permit Application Requirements for Lot

Coverage Calculations

As described in Tip 103, Site Plan Requirements and Tip

103A, Site Plan Guidelines, you must calculate the lot

coverage of existing and proposed development on your

lot and show it on the site plan that you are required to

submit with your application. If you are not sure of the

requirements, ask a Permit Specialist in the Applicant

Services Center for help.

HEIGHT

The base height of homes (principal structures) is 30 feet

above average grade (23.44.012).

On lots 30 feet or less in width, the base height is limited

to 25 feet (detailed measurement techniques are found

in Chapter 23.86 of the Land Use Code and in Direc-

tor's Rule 9-2011).

Pitched Roofs

The ridge of a pitched roof on a principal structure may

extend up to 5 feet above the base height limit as long as

the pitch of the roof is at least 4 to 12 (see Fig. A).

No portion of a roof with only one sloping plane may

extend beyond the base height limit (commonly known as

"shed roof" design").

Exemptions for Rooftop Features

Under certain conditions, radio and television antennas

and flagpoles are exempt from height limits.

Open rails and planters may extend no higher than the

ridge of a pitched roof or four feet above a flat roof. Pro-

jections that accommodate windows, such as dormers,

clerestories, skylights and greenhouses, may extend

no higher than the ridge of a pitched roof or four feet

above a flat roof provided that they are also limited to 30

percent of the area of the roof and meet separation and

setback standards discussed in 23.44.012C.

Chimneys may extend four feet above the ridge of a

pitched roof or above a flat roof. Additional exemptions

can be found in 23.44.012C.

Documenting Compliance with

Height Limits

All projects must demonstrate compliance with

applicable height limits for each structure on the site.

Height limits may vary depending on the location on

the property, and the use of the structure. The following

information should be incorporated into the plan set for

each structure proposed:

Average Grade – project plans need to document

average grade and how it was determined. There are

several options for calculating average grade, please re-

fer to Director’s Rule 9-2011 for a complete description

of the method for determining average grade.

Average Grade for Projects in a Shoreline Zone -

For projects located in a shoreline zone, please refer to

Land Use Code Section 23.60.952 for information about

how to determine average grade for a site.

Site Plan Documentation – Applicants will choose a

method for determining average grade. The site plan

needs to reflect all midpoint elevation grade points,

exterior wall lengths and the related calculations that are

required to fully document the average grade elevation

being used for height measurement purposes, based

on Director’s Rule 9-2011 or Land Use Code section

23.60.952. A stamped topographic survey, prepared

by a licensed surveyor, may be required if grade will be

disturbed for construction of the project and when any

exterior wall of the new structure, in the area where grade

is being disturbed, is within two feet of the allowed height

limit as measured above existing grade. A survey may

also be required if the grade information provided by an

SDCI Tip #220—Lot Coverage, Height, Yard & Garage Standards for Homes in Neighborhood Residential Zones page 3

LEGAL DISCLAIMER: This Tip should not be used as a substitute for codes and regulations. The applicant is responsible for compliance

with all code and rule requirements, whether or not described in this Tip.

applicant is not consistent with general site contours that

are reflected in city GIS systems.

Site plan documentation should also identify the follow-

ing elevation points depending on roof design:

n Roof ridge elevations or topmost elevation of a slop-

ing roof with a shed or butterfly roof

n Top of flat roof elevations

n Top of parapet or guardrail elevations

n Top most elevation of any feature extending above the

base height limit utilizing a height exemption, such as but

not limited to roof planters, clerestories, etc.

n Freestanding structures such as fences, bulkheads,

freestanding walls but not arbors.

Elevation View Documentation – Each building eleva-

tion drawing should incorporate the following elevation

information:

n Existing grade elevations at the “midpoints” used

in calculating the average grade.

n The average grade elevation and a line depicting

where this average grade lies in relation to the height

of the structure.

n Elevations for each floor level.

n Top plate elevations. For structures with a pitched

roof, which qualifies for a height exception, the base

height limit for the structure will be measured from

the average grade elevation to the top plate elevation

of the walls. All portions of roof above the height limit

must qualify for the pitched roof exceptions described

in the code for the zone or in the measurements sec-

tion of the code.

n Top of roof elevations. For structures that are not

utilizing a pitched roof exception, the elevation of the

highest element of the roof must be documented and

must be within the base height limit for the structure

plus exception for the roof.

Figure B

a=72'

D=60'

B EI 107.7

EI 106

106.3

D103

d=60'

Roof Ridge

E1 134

c=72'

126

top plate

fin grd

EI 132

1st Flr

EI 106

Top Plate

EI 126

Ridge

EI 134

Avg

Erd

EI 105.87

2nd Flr

EI 116

EI 132

Basement

EI 96'

28.13'

20.13'

Sample Calculation, Figures B and C

Formula 2: Average grade calculations, least rectangle

(A x a) + (B x b) + (C x c) + (D x d)

a + b + c +d

Figure C

Example:

(106 x 72) + (107.7 x 60) + (106.6 x 72) + (103 x 60)

72 + 60 + 72 + 60

(7632) + (6462) + (7675.2) + (6180)

264

Average grade = 105.87

SDCI Tip #220—Lot Coverage, Height, Yard & Garage Standards for Homes in Neighborhood Residential Zones

page 4

LEGAL DISCLAIMER: This Tip should not be used as a substitute for codes and regulations. The applicant is responsible for compliance

with all code and rule requirements, whether or not described in this Tip.

n Top of roof features. For portions of structures that

qualify for another type of height exception (such as,

but not limited to, clerestories, solar collectors, open

guardrails or planters), the elevation of the highest el-

ement of the feature must be documented and must

be within the allowable height limit plus exception for

the feature.

n Overall height dimension lines. Show dimension

lines from the average grade line, to the top plate, to

the top of roof and top of highest roof features.

n Exceptions to these height documentation require-

ments may be allowed in consultation with the plan

reviewer responsible for the zoning compliance and

shall be based on the specifics of each project.

YARDS (Land Use Code section 23.44.014)

Required Front Yard: 20 feet or the average of the

front yards of the single family residence on either side of

your lot, whichever is less.

Required Rear Yard: 25 feet, or 20 percent of lot

depth (minimum of 10 feet) whichever is less.

Required Side Yard: 5 feet. 10 feet for street facing

side yard of a reversed corner lot.

The Land Use Code requires that certain portions of your

lot be set aside for front, rear and side yards. In general,

no portion of your house may extend into these required

yards. You may place accessory structures such as

garages, sheds, decks, porches or arbors in these areas

only if certain criteria are met. Exceptions from standard

yard requirements are described in the following sec-

tions. Of course, you may provide more than the required

minimum yard. Yards are measured from the property line

in toward your structure. Property lines are not always

obvious. Do not rely on physical features such as fences

and sidewalks to indicate property lines. They may be on

your neighbor’s property or in the street right-of-way.

The basic yard requirements for neighborhood residential

zones are illustrated on Fig. D.

Additional requirements or exceptions may apply to a

yard that borders an alley, is a corner lot, has an irregular

shape, is a through lot (a lot with two street frontages

opposite of each other), or is on a sloping lot that is

greater than 35 percent. Please check the Land Use

Code or ask an Applicant Services Center staff member

for help if you have one of these conditions on your lot.

Figure D

SIDE YARD = 5'

REAR YARD = 25',

OR 20% OF LOT DEPTH

WHICHEVER IS LESS

FRONT YARD = 20',

OR THE AVERAGE OF

YARDS ON EITHER SIDE

DEPTH

LOT

Figure E

SDCI Tip #220—Lot Coverage, Height, Yard & Garage Standards for Homes in Neighborhood Residential Zones

page 5

LEGAL DISCLAIMER: This Tip should not be used as a substitute for codes and regulations. The applicant is responsible for compliance

with all code and rule requirements, whether or not described in this Tip.

Exceptions to Standard Yard Requirements

Additions to the principal structure in front, side

and rear yards (when the structure is already

built into that yard): If an existing structure is already

“nonconforming” with respect to a required yard, and

the nonconforming wall is at least 60 percent of the total

width of the respective facade, then the existing wall line

may be extended according to Sec. 23.44.014D4.

Additional conditions apply to front and rear yards. The

portion of an existing structure that is non-conforming

with respect to front or rear yard setbacks can be

increased, to a limited extent, in order to accommodate a

habitable basement or attic, per Sec. 23.42.112A1.

Projections into front yard on lots 30 feet or less:

On lots 30 feet or less in width, portions of the front

façade that begin 8 feet or more above finished grade

may project 4 feet into the required front yard. A mini-

mum 5-foot front yard must be provided (see Fig. E).

The chart on page 7 illustrates other possible exceptions

that may be applicable to your lot. Please check the

designated section of the Land Use Code for details.

Additional Information for Yard

Requirements And Exceptions

In addition to the specific references described in the

preceding table on page 7, there may be additional re-

quirements that are applicable to your project. Sections

23.44.016, 23.44.044 and 23.44.048 describe devel-

opment standards for structures that are permitted as

accessories to your home, such as garages, swimming

pools and solar collectors.

Measurement techniques are presented in Sections

23.86.008 and 23.86.010 and definitions of technical

zoning terms are found in Chapter 23.84A.

In addition, you should consult the Seattle Residential

Code and Seattle Building Code, which also regulates

construction close to the property line.

The Seattle Building Code (SBC) and the Seattle Resi-

dential Code (SRC) both regulate the construction of

buildings near property lines to prevent the spread of

fire. SBC Sections 602.1 and 704 and SRC section

R302 regulate the construction of walls, projections from

exterior walls and openings in walls near property lines.

Permit Application Requirements for

Yard Calculations

Your basic site plan will give the SDCI staff most of the

information it needs to check your plans for compliance

with yard requirements. Provide front yard information

(graphically show the dimensions on your plans) of

adjacent properties if you are averaging to determine your

required front yard. If your lot is sloping, you may need to

provide additional topographic information.

If you wish to take advantage of exceptions to yard

requirements that require an agreement or easement, you

must bring the agreement or easement with you.

Garages (23.44.016F)

Garage entrances on corner lots may be located on only

one street front. Garage width standards will be mea-

sured based on the width of the facade facing the same

street as the garage entrance.

The size and location of garages are regulated to reduce

their visual impact. The combined width of garage en-

trances on a street-facing façade may not be more than

50 percent of the structure width or 10 feet, whichever

is greater (see Fig. F). This standard does not apply to

detached garages located behind the principal home or

garages that face alleys.

SDCI Tip #220—Lot Coverage, Height, Yard & Garage Standards for Homes in Neighborhood Residential Zones page 6

LEGAL DISCLAIMER: This Tip should not be used as a substitute for codes and regulations. The applicant is responsible for compliance

with all code and rule requirements, whether or not described in this Tip.

Garages may not project beyond the front of a home.

Specifically, no attached garage wall may be closer to the

street lot line than 80 percent of the street-level façade

that is not a garage (see Fig G). If the entire street-level

façade is garage, no portion of the garage may be closer

to the street lot line than 80 percent of the façade of the

story above the street-level façade. The façade of a

building is measured from the outside of the exterior wall

and does not include eaves. Where the façade includes a

covered porch or deck, the façade will be measured from

exterior of the covered porch or deck.

Limited exemptions to the garage entrance standards are

allowed for sites with irregular lot shape, topography, or

structure configuration and are listed in 23.44.016 F3.

Figure F - Allowed Width of Garage

Allowed NOT AllowedNOT Allowed

Figure G - Garage Projections

SDCI Tip #220—Lot Coverage, Height, Yard & Garage Standards for Homes in Neighborhood Residential Zones page 7

LEGAL DISCLAIMER: This Tip should not be used as a substitute for codes and regulations. The applicant is responsible for compliance

with all code and rule requirements, whether or not described in this Tip.

Exception for: Permitted in: Features Code Section

Non-conforming principal

structure

Front or rear yard May be extended in order to ac-

commodate habitable basement

or attic

23.42.112A1

Principal structure Side yard Zero lot line with side yard ease-

ment

23.44.014C3

Detached accessory struc-

ture

Side yard Zero lot line with side yard agree-

ment with neighbor

23.44.014C2

Uncovered porches no higher

than 4 feet

Front, side or rear yards Various provisions

23.44.014C5

Chimneys, cornices, col-

umns, and eaves

Front, side or rear yards May project no more than 18

inches

23.44.014C6a

Bay windows Front, rear and street side

yards

May project no more than 2 feet;

limited to 8 feet in width

23.44.014C6b

(see also 6d)

Garden windows Front, side or rear yards Minimum of 30 inches above

floor, 6 feet tall and 8 feet wide

23.44.014C6c

(see also 6d)

Attached, covered and unen-

closed deck

Rear yard Various provisions

23.44.014C7

Garages Front, side or rear yard Various provisions

23.44.016D

(see also 016E, 016F)

Pedestrian access bridges Front, side or rear yard 5 feet in width, no less than 3

feet to the side lot line

23.44.014C8

Barrier-free access Front, side or rear yard Meeting WA State Building Code

C31

23.44.014C9

Fences, free-standing struc-

tures, bulkheads

Front, side or rear yard 6-foot height with additional

height with special conditions

23.44.014C10

Decks Front, side or rear yard No higher than 18 inches

23.44.014C11

Heat pumps Front, side or rear yard No closer than 3 feet to any lot

line

23.44.014C12

Solar collectors Front, side or rear yard 3 feet from side yard, 15 feet

from rear yard and 6 feet into

front

23.44.014C13 and

23.44.046

Critical areas Front and rear yards 25 percent reduction, up to a

maximum of 5 feet

23.44.014C15

Arbors Front, side or rear yards 40 sq. feet coverage with maxi-

mum 8 feet height, 50 percent

open

23.44.014C16a

Arbors Yards abutting a street 30 square feet coverage over

pedestrian walkway, 40 square

fee coverage with maximum 8

feet height, 50% open

23.44.014C16b

Arbors

Accessory Dwelling Units

Backyard Cottages

Yards abutting a street pedestrian walkway, 40 square

fee coverage with maximum 8

feet height, 50 percent open

23.44.014C16b

23.44.041