For Snohomish County, the roof snow load may be greater than or equal to 25 pounds per square foot (psf) depending on the elevation of the site location. Applicants for building permits must account for the ground snow load calculations, as verified by the Plans Examiner. Map algebra and raster calculations derived the Snow Load by multiplying the elevation times the Snow Load factor. These pixel-values represent the actual Snow Load calculation in psf at that spot.

[ Snow Load Calculation {psf} = (Snow Load Factor {pixel-value}) x (Elevation {ft.}) ]

As the American Society of Civil Engineers states that "in civil engineering, design loads are defined as the maximum amount that a structure can handle". Since the International Code Council (ICC), as with the historical Universal Building Codes (UBC), indicates in section 1608.2 that "Ground snow loads" for the area of Snohomish County falls under a Case Study (CS). The Washington Association of Building Officials (WABO) and Structural Engineers Association of Washington (SEAW) organizations have a White Paper which provides more detailed information. During the early 2000's, PDS Engineers and Plans Examiners decided on the iso-lines for the Snow Load factor. Further interpolations and vector-to-raster transformations occurred. In 2007, the Snohomish County Code (SCC) 30.52F.300TableR 301.2(1) was amended in to establish a Minimum Roof Snow Load of 25 psf. In 2015, the PDS created a web application (PDS Map Portal) that allows users to find Snow Loads at any given location as compiled in a PDS Property Report.