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Home My WebLink AboutROOF EVALUATION - 18-00665 - 618 Vale Ln - Roof Mounted Solar Panels/Main Service Panel Upgrade 55 WEST 500 SOUTH, HEBER CITY, UT 84032 T 925.787.3067 U RIGHTANGLEENG.COM November 26, 2018 Power Co 12227 Business Park Drive #100 Draper, UT 84020 RE: Structural Roof Evaluation for the Pheonix Residence: 618 Vale Lane, Rexburg, Idaho As per your request, we have evaluated the roof structure under the proposed solar panel array. The information used to evaluate this structure was gathered during a field visit by Power Co on behalf of Right Angle Engineering. The roof structure consists of pre-manufactured trusses spaced at 24” on center. The roof material consists of asphalt shingles. The design criteria used to analyze this structure are included with this letter. The adopted building codes in this jurisdiction are: the 2015 International Building Code, the 2015 International Existing Building Code, and ASCE 7-10. International Existing Building Code (IEBC) 2015 section 807.4 indicates that alterations to an existing building that results in less than a 5% increase in the total stress may be performed without a structural evaluation of the existing building. As demonstrated in the attached calculations, the additional weight of the solar panels will be less than 5% increase in the gravity loading and the stress on the existing roof framing. Based on our assessment we have determined that the existing roof framing will safely and adequately support the additional loads imposed by the solar panels. In order for the loads to be evenly distributed, the roof attachments should be staggered and spread evenly throughout the panel array. Attachment points vary from 24”-74”. The racking system should be installed per the manufacture’s specifications. There should be a minimum of 80 attachment points to the roof. Each attachment should have a 5/16” or 18/8 SS lag screw with 2.5” minimum penetration centered on each truss top chord. Waterproofing around the roof penetrations is the responsibility of others. Right Angle Engineering assumes no responsibility for improper installation of the solar panels. Regards, Robert D Smythe, P.E. Right Angle Engineering 11/26/18 2 Design Criteria: Design Wind Speed (3 second gust) 115 mph Exposure Category C Risk Category 2 Mean Roof Height 30 ft Roof Type Gable Roof Building Type enclosed Roof Dead Load- ASCE Table C3-1 asphalt shingles 2 psf 7/16" Plywood Sheathing 1.5 psf Roof Framing 4 psf Insulation 3.85 psf Gypsum sheathing 2 psf Solar Panel Array 3 psf Dead Load Without Panels 13.35 psf Dead Load With Solar panels 16.35 psf Roof Live Load Existing Roof Live Load 20 psf ASCE 7-10 Table 4-1 Roof Live Load with Solar Panels 0 psf 2015 IBC 1607.12.5 Roof Snow Load-ASCE 7-10 Ground Snow Load (pg) 50 psf Section 7.2 Exposure Factor (Ce) 0.9 Table 7-2 Thermal Factor (Ct) 1.1 Table 7-3 Importance Factor (Is) 1 Table 1.5-2 Flat Roof Snow Load (Pf) 35 Equation 7.3-1 Slippery surface Slope Factor (Cs) 0.75 Figure 7-2 Nonslippery Surface Slope Factor (Cs) 1 Figure 7-2 Snow Load Without Solar Panels 35 psf Equation 7.4-1 Snow Load With Solar Panels 26 psf Equation 7.4-2 Load Combinations - ASCE 7-10 Section 2.4-1 Without Solar Panels With Solar panels D + Lr 33.4 psf 16.4 psf D + S 48 psf 42.3 psf 3 Solar Array 1- Roof Slope 25 degrees Number of panels 40 Panel Area 700 ft^2 Wind Calculations- ASCE 7-10 GCp Zone 1 -0.9 Figure 30.4-(2A-5B) GCp Zone 2 -1.7 Figure 30.4-(2A-5B) GCp Zone 3 -2.6 Figure 30.4-(2A-5B) Gcpi 0.18 Table 26.11-1 Velocity Pressure (qh) 28.2 psf qh= .00256KhKhtKdV^2 Equation 30.3-1 Kh 0.98 Table 30.3-1 Kht 1 Equation26.8-1 Kd 0.85 Table 26.6-1 Designed wind pressure (P) psf Equation 30.9-1 P= qh(GCh) - (GChi)) Zone 1 Pressure (P) -30.5 psf Zone 2 Pressure (P) -53 psf Zone 3 Pressure (P) -78.4 psf Lag Screw Connection 5/16" Lag Screw Shear Capacity 190 lbs NDS 2015 Table 12K Shear max tributary area 15.5 ft^2 5/16" lag screw pullout capacity 266 lbs/in NDS 2015 Table 12.2A Lag screw embedment 2.5 in Total pullout capacity 665 lbs Pullout max tributary area 12.5 ft^2 Factor of safety 1.58 Minimum number of connections 80 Beam Stress IEBC 2015 Section 807.4 Beam Span 23 ft Spacing 2 ft Roof Framing type pre-manufactured trusses Number of Panels per rafter 4 Without Solar Panels With Solar Panels Percent Increase Bending Moment 6348 ft-lbs 3350.8 ft-lbs 52.8% Less than 105% Vertical Reaction (V1) 1104 lbs 676.5 lbs 61.3% Less than 105% Vertical Reaction (V2) 1104 lbs 444.9 lbs 40.3% Less than 105%