HomeMy WebLinkAbout114 Clear Brook STRUCTURAL REVIEW LETTER
Structural Group
J. Matthew Walsh, PE Kirk M. Nelson, SE Samuel Brown, PE - Civil
Director of Engineering Structural Engineering Structural Engineering
james.walsh@vivintsolar.com kirk.nelson@vivintsolar.com sam.brown@vivintsolar.com
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1800 W Ashton Blvd.
Lehi, UT 84043
January 29, 2020
Re: Structural Engineering Services
Frasier Residence
114 Clear Brook Rd, Yarmouth, MA
S-6298037; MA-03
To Whom It May Concern:
We have reviewed the following information regarding solar panel installation on the roof of the above referenced
home:
1. Site Visit by a representative from our office under my supervision identifying specific interior and
exterior site information including the condition of the existing roof system and the size, spacing, and
condition of existing structural framing members. Information gathered during the site visit includes
photographs, sketches, and verification forms.
2. Design drawings of the proposed PV System layout, including details to mount the new solar panels to
the existing roof.
Based on the above information, we have evaluated the structural capacity of the existing roof system to support the
additional loads imposed by the solar panels and have the following comments related to our review and evaluation:
A. Description of Residence:
The existing residence has typical wood framing construction with a maximum of two layers of composite shingle
roofing. All wood material utilized for the roof system is assumed to be Spruce-Pine-Fir #2 or better with standard
construction components. The designed areas of the home consist of the following framing methods:
• Roof Section 1: Prefabricated trusses at 24" on center. Survey photos indicate that there was free
access to verify the framing size and spacing.
• Roof Section 2: Prefabricated trusses at 24" on center. Survey photos indicate that there was free
access to verify the framing size and spacing.
B. Loading Criteria
10.02 PSF = Dead Load (roofing/framing)
3.00 PSF = Dead Load (solar panels/mounting hardware)
13.02 PSF = Total Dead Load
20 PSF = Roof Live Load
30 PSF = Ground Snow Load (based on local requirements)
Wind speed of 140 mph (based on Exposure Category B - the total area subject to wind uplift is calculated for the
Interior, Edge, and Corner Zones of the dwelling.)
C. Solar Panel Anchorage
1. Installation shall proceed in accordance with the applicable guidelines and recommendations indicated below.
If, during solar panel installation, the roof framing members appear unstable or deflect non-uniformly, our office
should be notified before proceeding with the installation.
• EcoFasten Solar Installation Manual, which can be found on the EcoFasten Solar website
(www.ecofastensolar.com).
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2. The solar panels are 1½" thick. At no time will the panels be mounted higher than 10" above the existing
surface of the roof.
3. The following mounting types shall be used. Please refer to the mounting details for the associated required
penetration depth. Based on our evaluation, the pullout demand is less than the maximum allowable per
connection and therefore is adequate.
• EcoFasten with Rock-It: (1) 5/16" lag screw. Pullout capacity based on National Design Specifications
(NDS) of timber construction specifications for Spruce-Pine-Fir is 235 lbs/inch penetration.
4. Fasteners are installed to meet industry standards and this document satisfies requirements in 2015 IBC
2303.4.5 verifying that the fasteners will not adversely affect the roof framing.
5. The maximum allowed spacing was calculated for the Wind Speed shown in paragraph B above, using the wind
load uplift procedures of ASCE 7-10 and is specified below. These spacing requirements apply to all mount
types indicated above. The following values have been verified by in-house testing and the mounting hardware
manufacturers' data, which are available upon request. Panel support connections should be staggered, where
possible, to distribute load to adjacent members.
Modules in Landscape Modules in Portrait
Roof Zone Interior Edge Corner Interior Edge Corner
Max Vertical Spacing (in) 40 40 40 66 66 66
Max Horizontal Spacing (in) 48 48 48 48 48 48
Max Uplift Load (lbs) 202 164 154 341 277 260
D. Summary
Based on the above evaluation, with appropriate panel anchors being utilized the roof system designed on will
adequately support the additional loading imposed by the solar panels, if installed correctly. This evaluation has
been performed for the structural elements only and verifies that they are in conformance with the 2015 International
Residential Code with Massachusetts Amendments, current industry standards and practice, and the information
supplied to us at the time of this report.
If there are any questions regarding the above, or if more information is required, please contact me.
Regards,
J. Matthew Walsh, PE
MA License No. 54057
01/29/2020