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Home My WebLink AboutLETTER Solar 727 Birdie Ln 2021-04-13___________________________________________________________________________________________ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530-864-7055 Domusstructural@gmail.com To: Namastѐ Solar 6707 Winchester Circle, Suite 700 Boulder, CO. 80301 Subject: Certification Letter Forschmiedt Residence 727 Birdie Ln Estes Park, CO. 80517 To Whom It May Concern, Design Criteria: ●Applicable Codes = 2015 IBC/IRC, ASCE 7‐10 ●Roof Dead Load = 8 psf (Roof 1) ●Roof Live Load = 20 psf ●Wind Speed = 175 mph (Vult), Exposure C, Risk Category II ● ● Sincerely, John Calvert, P.E. Project Engineer April 13, 2021 The roof structure of (Roof 1) consists of composition shingle on roof plywood that is supported by pre‐manufactured trusses that are spaced at @ 24"o.c.. The top chords, sloped at 23 degrees, are 2x6 sections, the bottom chords are 2x6 sections and the web members are 2x4 sections. The truss members are connected by steel gusset plates. The max unsupported projected horizontal top chord span is approximately 6'‐6''. The existing roof framing system of (Roof 1) is judged to be adequate to withstand the loading imposed by the installation of the solar panels. No reinforcement is necessary. Roof Snow Load = 67 psf The spacing of the solar standoffs should be kept at 48" o.c. for landscape and 24" o.c. for portrait orientation, with a staggered pattern to ensure proper distribution of loads. A jobsite observation of the condition of the existing framing system was performed by an audit team of Namastѐ Solar as a request from Domus Structural Engineering. All review is based on these observations and the design criteria listed below and only deemed valid if provided information is true and accurate. On the above referenced project, the roof structural framing has been reviewed for additional loading due to the installation of the solar PV addition to the roof. The structural review only applies to the section of the roof that is directly supporting the solar PV system and its supporting elements. The observed roof framing is described below. If field conditions differ, contractor to notify engineer prior to starting construction. The scope of this report is strictly limited to an evaluation of the fastener attachment, underlying framing and supporting structure only. The attachment's to the existing structure are required to be in a staggered pattern to ensure proper distribution of loading. All panels, racking and hardware shall be installed per manufacturer specifications and within specified design limitations. All waterproofing shall be provided by the manufacturer. Domus Structural Engineering assumes no responsibility for misuse or improper installation of the solar PV panels or racking. Please contact me with any further questions or concerns regarding this project. Note: Seismic check is not required since Ss<.4g and Seismic Design Category (SDC) < B Attachment: 1 ‐ 5/16 dia. lag screw with 2.5 inch min. embedment depth, at spacing shown above. Forschmiedt Residence Estes Park CO.xlsm 1 APPROVED by SAFEbuilt; 2015 International Codes Subject to inspection and compliance to all Relevant, adopted Building & Municipal Codes 05/06/2021 ____________________________________________________________________________________ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530-864-7055 Domusstructural@gmail.com 67 psf (ASCE7 - Eq 7-1) 1 (ASCE7 - Table 7-2) 1 (ASCE7 - Table 7-3) 1 67.0 psf (ASCE7 - Eq 7-2) 1 67.0 psf 3.26 psf 3.0 psf 2.00 ft 2.75 ft 5.50 sft 17 lb 4.00 2.00 1.15 0.00 (Ceiling Not Vaulted) 0.85 8.0 psf 8.7 psf Gravity Loading PV System Weight Weight of PV System (Per Namaste Solar) X Standoff Spacing = Y Standoff Spacing = Note: PV standoffs are staggered to ensure proper distribution of loading 2x6 Top Chords @ 24"o.c. I = Importance Factor = Cs = Slope Factor = Standoff Tributary Area = ps = Cspf ps = Sloped Roof Snow Load = pf = Flat Roof Snow Load = DL Adjusted to 23 Degree Slope Roof Snow Load Calculations pg = Ground Snow Load = Ce = Exposure Factor = pf = 0.7 Ce Ct I pg Ct = Thermal Factor = Roof Live Load = 20 psf Roof Plywood Roof Dead Load (Roof 1) Composition Shingle Note: Roof live load is removed in area's covered by PV array. DL Adjusted to 23 Degree Slope Point Loads of Standoffs Miscellaneous Vaulted Ceiling Total Roof DL (Roof 1) PV Dead Load = 3 psf (Per Namaste Solar) Forschmiedt Residence Estes Park CO.xlsm 2 Reviewed by SAFEbuilt 05/06/2021 ___________________________________________________________________________________________ Domus Structural Engineering, LLC P.O. Box 6986 Broomfield, CO 80021 530-864-7055 Domusstructural@gmail.com 175 mph C Hip/Gable 23 degrees 20 ft 19.3 ft (Eq. 30.3-1) 0.9 (Table 30.3-1) 1 (Fig. 26.8-1) 0.85 (Table 26.6-1) 175 mph (Fig. 26.5-1A) II (Table 1.5-1) qh = 59.98 35.99 Zone 1 Zone 2 Zone 3 Positive GCp = -0.84 -1.39 -2.23 0.38 (Fig. 30.4-1) Uplift Pressure = -30.16 psf -50.02 psf -80.18 psf 22.6 psf X Standoff Spacing = 2.00 2.00 1.33 Y Standoff Spacing = 2.75 2.75 2.75 Tributary Area = 5.50 5.50 3.67 Footing Uplift = -166 lb -275 lb -294 lb Zone 1 Zone 2 Zone 3 Positive GCp = -0.84 -1.39 -2.23 0.38 (Fig. 30.4-1) Uplift Pressure = -30.16 psf -50.02 psf -80.18 psf 10.0 psf (Minimum) X Standoff Spacing = 4.00 4.00 2.67 Y Standoff Spacing = 1.75 1.75 1.75 Tributary Area = 7.00 7.00 4.67 Footing Uplift = -211 lb -350 lb -374 lb -374 lb 450 lb Therefore, OK Fastener =1 - 5/16" dia. lag Number of Fasteners = 1 Embedment Depth = 2.5 Pullout Capacity Per Inch = 250 lb Fastener Capacity = 625 lb w/ F.S. of 1.5 & DOL of 1.6= 667 lb Therefore, OK Wind Calculations Maximum Design Uplift = Standoff Uplift Capacity = 450 lb capacity > 374 lb demand Fastener Capacity Check Standoff Uplift Check Kz (Exposure Coefficient) = Kzt (topographic factor) = Kd (Wind Directionality Factor) = V (Design Wind Speed) = Risk Category = qh = 0.00256 * Kz * Kzt * Kd * V^2 Wind Pressure P = qh*G*Cn Exposure Category Per ASCE 7‐10 Components and Cladding Mean Roof Height Roof Slope 667.2 lb capacity > 374 lb demand 0.6 * qh = Standoff Uplift Calculations-Landscape Input Variables Wind Speed Effective Wind Area Design Wind Pressure Calculations Roof Shape Standoff Uplift Calculations-Portrait Forschmiedt Residence Estes Park CO.xlsm 3 Reviewed by SAFEbuilt 05/06/2021 Lateral Capacity of Standoffs - Portrait 364 lb 250 lb (Z parralel using SPF lumber with 1/4" side plate) 250 lb 250 lb 67 psf 23 deg 26.18 psf 2 39.10 in 250 lbs 35.17 in 24 in Lateral Capacity of Standoffs - Landscape 364 lb 250 lb (Z parralel using SPF lumber with 1/4" side plate) 250 lb 250 lb 67 psf 23 deg 26.18 psf 2 22.00 in 250 lbs 62.51 in 48 in Maximum Standoff Capacity Number of Rails = Y Standoff Spacing = Nominal Lateral Lag Capacity (NDS) = Snow Load = Allowable Lateral load per standoff = Snow Load = Roof slope = Maximum Standoff Spacing Lateral Snow Load on Standoff Standoff Shear Capacity (Manufacturer) = Nominal Lateral Lag Capacity (NDS) = Actual Lateral Lag Capacity (NDS) = Governing Lateral Capacity = Number of Rails = Maximum Standoff Spacing Actual Lateral Lag Capacity (NDS) = Governing Lateral Capacity = Max Allowable Standoff Spacing = Actual Spacing = Actual < Allowed, Therfore OK Maximum Standoff Capacity Standoff Shear Capacity (Manufacturer) = Lateral Snow Load on Standoff Roof slope = Y Standoff Spacing = Allowable Lateral load per standoff = Max Allowable Standoff Spacing = Actual Spacing = Actual < Allowed, Therfore OK Reviewed by SAFEbuilt 05/06/2021