ENG REPORT ON BLDG Roof Assessment for Solar Panel Installation C D R+A
Report Date: March 14, 2018 Structural Engineers(/
Prepared for: Ms. Emma Cowie, Energy Conservation Solutions It 4373/
116 Gasoline Alley, Suite 109, Mooresville, NC 28117
Project Number: 180124 ECS Kosik Metal 26pT
Assessment Date: March 14, 2018
Site Address: 5542 Cokesbury Rd., Fuquay Varina, NC 27526
Purpose: Structural Roof Assessment for installation of 35 panel solar array.
Prepared by: Clay Medlin & Clinton Robertson, PE, NC #032084
NC COL: C-3298, CDR&Assoc., Inc.
p_torn rrrrrrr
•
:CDR & ASSOC.,‘ ?
0: INC.
t No. C-3298 :Q'
�ti•�TfOFAt11 `•. 7?`
wg4uuNpN
CDR &Assoc., Inc. thanks you for the opportunity to provide you with a letter for the
inspection of the roof framing for the installation of solar panel system on the roof of the
foresaid property hereafter referred to as "building". All references to directions or
locations indicated in this report are by facing the front of the building.
Observations and Analysis of Roof
• Roof Construction: A layer of metal roof decking over metal 24 Ga. Trusses spaced at
5-0"on center.
• Roof Pitch: 3 in 12 pitch (approximately).
• Solar Panel Array: 35 panels.
• Total Array Square Footage: The panels are approximately 39.37"x 64.57" or 17.65 sf
each, round up to 18 sf x 35 panels=total surface area of 630 sf.
• Total weight of Array: Panel weighs approximately 40 lbs. ea. X 35 = 1400 lbs. for the
Array.
• Total Additional Weight on Roof: 1400 lbs/630 sf= 2.22 psf add for rail mount
system, assume 3 psf additional load on roof structure.
• Rail Mount System: The panels are mounted on aluminum rails(UNIRAC
SOLARMOUNT or Renusol PV)at top and bottom of the panels for each row of panels.
CDR+A I Structural Engineering 18611 Concord Mills Blvd. I Suite 1601 Concord.NC 280271(980)224-2237 I wwa'.CDR-A.com
Energy Conservation Solutions CDR+A
Roof Structural Assessment
Structural Engineers
• Analysis of Roof Structure:
o Additional dead load (12 psf roof framing + 3 psf array= 15 psf)
o Roof Live Load or equivalent snow load-20 psf. (Allowable Residential Code
w/o reductions)
o The loads mentioned above are less than or equal to the design loads provided
in the construction documents for the metal building.
• Wind Speed: Components and cladding 90 mph wind load uplift of-18 psf.
• Total Wind Load Uplift: -18 psf x 630 sf= 11,340 lbs total uplift for solar array.
• Number of Attachment Anchors: Use a minimum of one S-5! Versa-Bracket with three
Simpson Strong Drive XL Large Head Metal Screws#12x1 '/a" (or equvilent), per 5'-0"; 6
per rail x 4 rails(top and bottom)= 24 total attachment brackets.
• Wind Load Uplift per Anchor: 11,340 lbs total uplift/24 =473 lbs for solar array.
• Strength of Hold-down Anchors: The S-5! Versa-Bracket and three Simpson Strong
Drive XL Large Head Metal Screws#12x1 Y:' should be placed into the top of the metal
truss members. The load testing results determined an average pullout failure load of
1485 lbs. Using a safety factor of 2.5 the maximum allowable load on the bracket is
1485 lbs/2.5 = 742 lbs exceeding the required 473 lbs per bracket.
Conclusions & Recommendations
By analysis the roof truss members were determined to be able to support the additional loads
imposed by the solar panel array. I do not recommend any other remedial actions for the roof
structural framing system at this time.
The installation of the solar panel array using UNIRAC SOLARMOUNT or Renusol PV
aluminum rails and 5.51 Versa-Bracket and three Simpson Strong Drive XL Large Head
Metal Screws#12x1 1/i" is adequate for the loads imposed on them. Please see attached
documentation.
Closure
We appreciate the opportunity to provide structural assessment services to you. Please contact
us should you have any questions.
Sincerely,
Clinton D. Robertson, PE, LEEDS AP
R9 I=