David Caruso Letter for Structural Assessment Revised 9-1-23Vreeland Design Associates
An integrative approach to design engineering and site planning
116 River Road, Leyden, MA 01337 Phone: (413) 624-0126
Email: dvreeland@verizon.net Fax: (413) 624-3282
Date: September 1, 2023
To: Justin Annis
NorthEast Solar
136 Elm Street
Hatfield, MA 01038
From: David Vreeland, P.E.
Vreeland Design Associates
Re: David Caruso, 66 Franklin Street, Northampton, MA: Structural assessment of existing
house roof to support the proposed PV solar panel array.
I have investigated the existing roof framing in the area of the proposed PV solar panel
installation. The original 2-story, 24’x 32’ house was constructed around 1892. 17 PV solar panels
are to be installed on the south facing roof of the main house. The house roof is framed with full
dimension 2x5 rafters installed 24” on-center, spanning 11’-6” with a 7/12 pitch. A 6x6 purlin
beam located near the mid-span of the rafters span the length of the house supported with a 2x6
post located 17’-8” from a gable end. A 6x6 tie-beam is secured to the top of the purlin beam 16’
in from the gable ends preventing the purlin beams from bowing. 2x6 ceiling joists located 20”
above the top of the exterior walls are secured to the rafters preventing the roof from spreading.
The roofing is composite asphalt shingles.
The purlin beam is undersized to support the solar panels and meet the requirements of the current
building code. I have calculated the maximum load that the existing purlin beam can carrying and
be in compliance with the building code. The existing rafters will need to be reinforced to
adequately support the roof loads and not over load the purling beam. Reinforce the south rafters
supporting the solar panels by sistering 2x6 x 6’ centered over the purlin beam nailed with 2 – 12d
nailgun nails at 6” on-center or 2 – 2-7/8” HeadLok or similar structural screws at 12” on-center
along the length of the 2x6s. Notch the 2x6 as little as possible to be able to rotate the 2x6 into
place over the purlin beam.
I have reviewed the mounting details for the proposed PV solar panel array. Based on my
calculations and a PV solar panel unit weight of 46± lbs, with the attachment points of the array
placed at a maximum of 4’ on center and staggered to minimize the load to any one rafter, the
reinforced house roof framing, as outlined above, is adequate to support the proposed PV solar
panel array and the 40 psf ground and 35 psf roof snow loads and the 117 mph Vult basic wind
speed requirements of the current 9th Edition of the MA State Building Code for the City of
Northampton.
Please contact me if you have any questions or need additional information.
Sincerely,
David Vreeland, PE
Vreeland Design Associates
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