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16-04-500 -- 16-04-506 KING COUNTYPUBLIC RULESDEPARTMENT OF DEVELOPMENT AND ENVIRONMENTAL SERVICESChapter 16-04Rules and Regulations of theDepartment of Development and Environmental ServicesStructural Loading: Minimum Roof Snow Loads Effective Date: October 22, 2001 Sections:16-04-500 Purpose16-04-503 Definitions16-04-506 Application16-04-509 Severability 16-04-500 Purpose. It is the purpose of this rule toimplement the provisions of K.C.C. 16.04.05046 or itssuccessor subsection by establishing the roof snow loadcriteria. The minimum roof snow load in King County is 25psf as defined in K.C.C. 16.04.05046. 16-04-503 Definitions. A. Department. “Department” means the Department ofDevelopment and Environmental Services of King County.B. Roof Snow Load. “Roof Snow Load” means the weightof snow that is used for the design of a building orstructure.C. Ground Snow Load. “Ground Snow Load” means theweight of snow on the ground. 16-04-506 Application. A. Ground Snow Load. The groundsnow load, P g , shall be determined in accordance with thefollowing formula:P g = C g h msl (506-1) WHERE: C g = Ground snow load coefficient determined byinterpolating the isolines established in the “KingCounty Ground Snow Load Map.” For locations listed in KING COUNTYPUBLIC RULESDEPARTMENT OF DEVELOPMENT AND ENVIRONMENTAL SERVICESStructural Loading: Minimum Roof Snow LoadsPage 2Effective Date: October 22, 2001 16-04-506Table 16-V (Unincorporated King County Ground SnowLoads) the isoline values in the table shall be used.h msl = Site elevation, feet above sea level.The building official shall have the authority to establishalternate ground snow loads based on station data or siteexperience.B. Determining “ Roof Snow Loads .” Roof snow loadsshall be calculated in accordance with one of the following: 1.SEAW, Snow Load Analysis for Washington, SecondEdition, provided that the snow exposure factor,C e , shall be determined from Table 16-W. 2.UBC 1997 Vol. II, Appendix Chapter 16 Division I,provided that the snow exposure factor, C e , shallbe determined from Table 16-W. 3.ASCE 7-98 Section 7. For buildings and other structures with a site elevation notgreater than 1000 feet, it shall be permitted to determinethe roof snow load (P f ) in accordance with the followingformula:P f = C e IP g (506-2) WHERE: P g = Ground snow load in accordance with K.C.C.16.04.506 paragraph A.I = Occupancy Importance Factor in accordance withTable 16-X.C e = Snow Exposure Factor in accordance with Table16-W.For all buildings and structures in King County, the roofsnow load shall not be less than 25 psf.C. Drift snow load and sliding snow load shall beconsidered for: KING COUNTYPUBLIC RULESDEPARTMENT OF DEVELOPMENT AND ENVIRONMENTAL SERVICESStructural Loading: Minimum Roof Snow Loads Page 3Effective Date: October 22, 2001 16-04-506 1.Buildings and other structures in OccupancyCategory 1–Essential Facilities. See UBC 1997,Table 16-K. 2.Buildings in Occupancy Group A with an occupantload of 300 or more in one room. 3.Buildings and other structures with a siteelevation greater than 1000 feet. 4.Buildings and other structures with an unusualroof configuration that may result in substantialsnow drift loads.D. Roof snow loads shall be included in the seismicanalysis as follows: 1.For roof snow loads not greater than 30 psf, theseismic gravity load, W, need not include the roofsnow load. 2.For roof snow loads between 30 and 100 psf, theseismic gravity load, W, shall include not lessthan 25% of the roof snow load. 3.For roof snow loads greater than or equal to 100psf, the seismic gravity load, W, shall includenot less than 30% of the roof snow load.The building official shall have the authority to make finaldetermination of snow loads by considering site location,roof configuration, and occupancy. TABLE 16-V: (Unincorporated King County Ground Snow Loads) LOCATIONISOLINE VALUE Auburn0.05Bellevue0.05Bothell0.05Black Diamond0.05Carnation0.057Duvall0.056Enumclaw0.05Fall City0.073Issaquah0.054Kent0.05Kirkland0.05Lester0.072 KING COUNTYPUBLIC RULESDEPARTMENT OF DEVELOPMENT AND ENVIRONMENTAL SERVICESStructural Loading: Minimum Roof Snow LoadsPage 4Effective Date: October 22, 2001 16-04-506North Bend0.075Palmer0.063Renton0.05Seattle0.05Skykomish0.094Snoqualamie Pass0.144Stevens Pass Ski Area0.10Vashon Island0.05 TABLE 16-W: Snow Exposure Coefficient (C e )1. Building located in generally open terrainand with roof slopes of 3 units vertical in12 units horizontal (25% slope) or greater. 0.82. All other structures.1.0 TABLE 16-X: Values for Occupancy Importance Factor II Type of Occupancy SNOW 1. Essential facilities. 1.152. Any building where the primary occupancy isfor assembly use for more than 300 persons(in one room).1.153. Agricultural buildings, productiongreenhouses and other miscellaneousstructures.0.94. All others. 1.0 16-04-509 Severability. If a provision of the rulescontained herein or its applicability to any person orcircumstance is held invalid, the remainder of theprovisions of these rules or the application of theprovision to other persons or circumstances shall not beaffected.
