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SLING <br />CO <br />CONSULTILTI NG <br />Scott E. Wyssling, PE <br />Coleman D. Larsen, SE, PE <br />Gregory T. Elvestad, PE <br />Revolution Solar <br />9981 West 19011 Street <br />Unit K, Mokena, IL <br />To Whom It May Concern: <br />76 North Meadowbrook Drive <br />Alpine, UT 84004 <br />office (201) 874-3483 <br />swyssling@wyssfingconsulting.com <br />October 10, 2022 <br />Revised October 31, 2022 <br />Re: Engineering Services <br />Hollcraft Residence <br />21E East McGill Avenue, Everett, WA <br />14.400 kW System <br />We have received information regarding solar panel installation on the roof of the above referenced <br />structure. Our evaluation of the structure is to verify the existing capacity of the roof system and its ability <br />to support the additional loads imposed by the proposed solar system. <br />A. Site Assessment Information <br />1. Site visit documentation identifying attic information including size and spacing of framing <br />for the existing roof structure. <br />2. Design drawings of the proposed system including a site plan, roof plan and connection <br />details for the solar panels. This information will be utilized for approval and construction <br />of the proposed system. <br />B. Description of Structure: <br />Roof Framing: Prefabricated wood trusses at 16" on center. All truss members are <br />constructed of 2x6 dimensional lumber. <br />Roof Material: Composite Asphalt Shingles <br />Roof Slope: 25 degrees <br />Attic Access: Accessible <br />Foundation: Permanent <br />C. Loading Criteria Used <br />• Dead Load <br />o Existing Roofing and framing = 7 psf <br />o New Solar Panels and Racking = 3 psf <br />o TOTAL = 10 PSF <br />• Live Load = 20 psf (reducible) — 0 psf at locations of solar panels <br />• Ground Snow Load = 15 psf <br />• Wind Load based on ASCE 7-16 <br />o Ultimate Wind Speed = 98 mph (based on Risk Category II) <br />o Exposure Category C <br />Analysis performed of the existing roof structure utilizing the above loading criteria is in accordance <br />with the 2018 Washington State Residential Code (20181RC), including provisions allowing existing <br />structures to not require strengthening if the new loads do not exceed existing design loads by <br />105% for gravity elements and 110% for seismic elements. This analysis indicates that the existing <br />framing will support the additional panel loading without damage, if installed correctly. <br />