18C-033 (3) Richard B. Gordon, P.E.
P.O.Box 264.Farmville.VA 23901
Ph: 434.394.2326.E-mail: grichardpe@aol.com
0 June 26, 2017
Northampton Building Department
Northampton, MA Re: Solar Panels Roof Structural Framing Support
To Whom It May Concern:
I hereby certify that I am a Licensed Professional Engineer in the State of Massachusetts. Please note the following
conclusions regarding framing structure,roof loading,and proposed site location of installation:
1. Existing roof framing:
Roof 1: Conventional wood framing is 2x6 at 16"o.c.with 11'-9"span (horizontal rafter projection)
Roof 2: Conventional wood framing is 2x6 at 16"o.c.with 6'span(horizontal rafter projection)
This existing structure is definitely capable to support all of the loads that are indicated below for this
photovoltaic project after sister only roof 1 rafters with a 2x4 using(2)1Od nails 1'c.c. Use of(2)Guard
Dog" FMGD002 screws is approved,or equal shear strength of approx. 120 Ib, 1'c.c.at areas where little
space is available only with remainder of member secured with (2)10d nails 1'c.c. If do not sister,then
install a 2x4 @ 16" o.c. knee wall over an interior bearing wall to limit span of rafters between supports to 10'-
10".
2. Roof Loading
• 4.33 psf dead load(modules plus all mounting hardware)
• 24 psf snow live load (40 psf ground snow live load reference)
• 6.2 psf dead load roof materials with knee wall and 7.3 psf if sister with 2x4(3 psf fiberglass
shingles, 1.5 psf%"wood sheathing, 1.7 psf 2x6,1.1 psf 2x4)
• Exposure Category B, 106 mph wind uplift live load of 16.6 psf(wind resistance)
3. Address of proposed installation: Residence of Constance Bushey, 34 Cooke Ave, Northampton, MA
This installation design will be in general conformance to the manufacturer's specifications,and is in compliance
with all applicable laws,codes,and ordinances, and specifically, International Residential Code/IRC 2009. The
spacing and fastening of the mounting brackets is to have a maximum of 64"o.c.span between mounting brackets
and secured using 5/16"diameter corrosive resistant steel lag bolts. In order to evenly distribute the load across the
roof rafters, there shall be a minimum of 2 mounting brackets per rafter&min. 3" penetration of lag bolt per bracket,
which is adequate to resist all 106 mph wind live loads including wind shear. Per NDS Section 11.1.4 clearance holes
equal to the diameter of the shank need to be bored into primary framing member for the full length to the threaded
portion of the screw to avoid splitting of framing member.
Very truly yours,
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Richard B. G ' P. .
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Massac - .:[7•' .L ense No.49993 •;.
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