17C-004 (2) Optimize Engineering Co., LLC
P.O. Box 264•Farmville•VA 23901
Ph: 434.574.6138.E-mail: grichardpe @aol.com
/
Richard B. Gordon, P.E. Tf
President
August 6, 2015
Florence Building Department
Florence, 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: Conventional framing is 2x6 at 24" o.c.with 12'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 rafters with a 2x6 using(2)10d nails V o.c. Use of(2)
Guard DogTm FMGDO02 screws is approved,or equal shear strength of approx. 120 lb, V o.c.at areas
where little space is available only with remainder of member secured with(2)10d nails V o.c. If do
not sister,then install a 2x4 @ 24"o.c. knee wall over an interior bearing wall to limit span of rafters
between supports to V-9".
2. Roof Loading
• 4.33 psf dead load(modules plus all mounting hardware)
• 33 psf snow live load(55 psf ground snow live load reference)
• 4.5 psf dead load roof materials
• Exposure Category B, 115 mph wind uplift live load of 19.6 psf(wind resistance)
3. Address of proposed installation: Residence of Romney Biddulph, 17 Warren St., Florence,
Massachusetts
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 2009,2011 NEC,and 2012 ICC Energy Code. The spacing and fastening of the Unirac mounting
brackets is to have a maximum of 64" o.c.span along the rail between mounting brackets and secured using
5/16"x 3'/z" length 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.2" penetration of lag bolt per
bracket,which is adequate to resist all 115 mph wind live loads including wind shear. The mounting
brackets shall alternate between adjacent rafters between rail rows for better distribution of roof load.
Penetration of anchors for modules mounted within 18"of ridge and edges of roof is to be a minimum of 3".
Rails may be attached to either of two mounting holes in the L-feet. Mounting in the lower hole for a low
profile, more aesthetically pleasing installation or mount in the upper hole for a higher profile to maximize
airflow under the modules to cool them more.Slide the"-inch mounting bolts into the footing bolt slots.
The rails will be attached to the footings with the flange nuts.
Very truly yours,
Optimize Engineering Co., LLC
Richard B.G dv , P.E. „P,_TH OF���
Massachusetts P.E. Lice se No.49993
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