23.86.006

A. In all zones except downtown zones, and except for the Living Building Pilot Program authorized by Section 23.40.060 , unless otherwise specified, the height of structures shall be measured according to this subsection 23.86.006.A. 1. General rule. Except as otherwise specified, the height of a structure is the difference between the elevation of the highest point of the structure not excepted from applicable height limits and the average grade level. In this subsection 23.86.006.A, "average grade level" means the average of the elevation of existing lot grades. Except as provided in subsection 23.86.006.A.2, average grade level is calculated, at the discretion of the applicant, as follows: a. at the midpoint, measured horizontally, of each exterior wall of the structure, or b. at the midpoint of each side of the smallest rectangle that can be drawn to enclose the structure. 2. Option for calculating average grade level to measure height. The calculation of structure height in subsection 23.86.006.A.1 may be modified, at the discretion of the applicant, as follows to permit the structure to respond to the topography of the lot: a. Draw the smallest rectangle that encloses the principal structure. b. Divide one side of the rectangle, chosen by the applicant, into sections at least 15 feet in length using lines that are perpendicular to the chosen side of the rectangle. c. The sections delineated in subsection 23.86.006.A.2.b are considered to extend vertically from the ground to the sky. d. The maximum height for each section of the structure is measured from the average grade level for that section of the structure, which is calculated as the average elevation of existing lot grades at the midpoints of the two opposing exterior sides of the rectangle for each section of the structure. B. Within the South Lake Union Regional Center, at the applicant's option, structure height shall be measured either as provided for in subsection 23.86.006.A or 23.86.006.D, or under provisions of this subsection 23.86.006.B. Structure height shall be measured for all portions of the structure. All measurements shall be taken vertically from existing or finished grade, whichever is lower, to the highest point of the structure located directly above each point of measurement. Existing or finished grade shall be established by drawing straight lines between the corresponding elevations at the perimeter of the structure. The straight lines will be existing or finished grade for the purpose of height measurement. When a contour line crosses a facade more than once, that contour line will be disregarded when establishing existing or finished grade. C. Stories or portions of stories of a structure that are underground are not analyzed for purposes of structure height measurement. D. Height measurement techniques in downtown zones and in the South Lake Union Urban Center 1. Determine the major street lot line, which shall be the lot's longest street lot line. When the lot has two or more street lot lines of equal length, the applicant shall choose the major street lot line. 2. Determine the slope of the lot along the entire length of the major street lot line. 3. Measure the maximum height as follows: a. When the slope of the major street lot line is less than or equal to 7.5 percent, the elevation of maximum height shall be determined by adding the maximum permitted height to the existing grade elevation at the midpoint of the major street lot line. On a through-lot, the elevation of maximum height shall apply only to the half of the lot nearest the major street lot line. On the other half of a through-lot, the elevation of maximum height shall be determined by the above method using the street lot line opposite and parallel to the major street lot line as depicted in Exhibit A for 23.86.006 . Exhibit A for 23.86.006 Maximum height Slope Less than or equal to 7-1/2 percent b. When the slope of the major street lot line exceeds 7.5 percent, the major street lot line shall be divided into four or fewer equal segments no longer than 120 feet in length. The elevation of maximum height shall be determined by adding the maximum permitted height to the existing grade elevation at the midpoint of each segment. On a through-lot, the elevation of maximum height shall apply only to the half of the lot nearest the major street lot line. On the other half of a through-lot, the elevation of maximum height shall be determined by the above method using the street lot line opposite and parallel to the major street lot line, as depicted in Exhibit B for 23.86.006 . Exhibit B for 23.86.006 Maximum height Slope greater than 7-1/2 percent c. For lots with more than one street frontage, where there is no street lot line that is essentially parallel to the major street lot line, when a measurement has been made for the portion of the block containing the major street lot line, the next measurement shall be taken from the remaining street lot line that is opposite and most distant from the major street lot line. E. Determining the height of existing public school structures. When the height of the existing public school structure is measured for purposes of determining the permitted height or lot coverage of a public school structure, either of the following measurement methods may be used: 1. If all parts of the new roof are pitched at a rate of not less than 4:12, the ridge of the new roof may extend to the highest point of the existing roof. A shed roof does not qualify for this option; or 2. If all parts of the new roof are not pitched at a rate of not less than 4:12, then the elevation of the new construction may extend to the average height of the existing structure. The average height shall be determined by measuring the area of each portion of the building at each height and averaging those areas, as depicted in Exhibit C for 23.86.006 . Exhibit C for 23.86.006 Maximum elevations for additions to public schools F. Height measurement technique for structures located partially within the Shoreline District. When any portion of the structure falls within the Shoreline District, structure height for the entire structure shall be measured according to Section 23.60A.952 . G. For projects accepted into the Living Building Pilot Program authorized pursuant to Section 23.40.060 , the applicant may choose either the height definition of Chapter 2 of the Seattle Building Code or the height measurement method described in this Section 23.86.006 . (Ord. 127376 , § 92, 2025; Ord. 127375 , § 110, 2025; Ord. 126685 , § 64, 2022 [cross-reference update]; Ord. 126509 , § 93, 2022 [zone name change]; Ord. 125603 , § 80, 2018; Ord. 125272 , § 68, 2017; Ord. 124843 , § 65, 2015; Ord. 124172, § 66, 2013; Ord. 123649, § 64, 2011; Ord. 123564, § 12, 2011; Ord. 123495, § 94, 2011; Ord. 123206, § 7, 2009; Ord. 122823, § 12, 2008; Ord. 122582 , § 3, 2007; Ord. 121476, § 24, 2004; Ord. 121359, § 10, 2003; Ord. 112971, § 1, 1986; Ord. 112539, § 13, 1985; Ord. 112519, § 51, 1985; Ord. 112303, § 24, 1985; Ord. 111926, § 25, 1984; Ord. 110669, § 26, 1982; Ord. 110570, § 21, 1982; Ord. 110381, § 1, 1982.)