Page, Kathleen- EL REVNorthampton, MA
212 Main St.
Northampton, MA 01060
10 Laurel Street
Northampton, MA 01060
RE: STLAURENCE, JANICE; DELUE, CHRISZEL
Trinity Solar | 4 Open Square Way, Suite 410 | Holyoke, MA | (413) 203-9088
MA License No. 56687
To the Building Official:
The following information constitutes a summary of the relevant design criteria and recommendations for the support of a
new photovoltaic [PV] system on the existing roof framing components at the above-referenced location.
Criteria is as follows:
1.Existing roof framing:
Conventional roof framing at R1 is 2x6 at 20 o.c.; existing rafter span= 12' 6"; (horizontal projection)
Conventional roof framing at R3 is 2x6 at 20 o.c.; existing rafter span= 8' 0"; (horizontal projection)
2.Roof Loading:
• 3.0psf dead load (pounds per square foot - PV panels, mounting rails & hardware)
• 5.7psf - existing roof loads (1.7 psf - 2x6 framing, 1.5psf roof sheathing, 2.5 psf shingles)
• Ground Snow Load - 40psf - per AHJ (Authority Having Jurisdiction)
• Wind criteria - Exposure Category B, 117 mph wind
3. Existing roof modification at R1 only - provide 2x4 (@16" o.c.) "knee wall" reinforcing to limit the maximum span of
the existing rafter to 9'-9". Locate bottom of "knee wall" within one foot of existing bearing wall below. Alternatively, "
sister" existing rafters with new 2x6 rafters extending the full length of the existing rafters and terminated before the
existing rafter support connection. Non-full-length rafter sisters must "overlap" its accompanied sister a minimum of 24"
with nailing from each side in the overlap.
This installation design is in general conformance with the manufacturers’ specifications and complies with all
applicable laws, codes, and ordinances – specifically the International Building Code (2015 edition) and the
International Residential Code (2015 edition), including all Massachusetts regulations and amendments.
The spacing and fastening of the mounting brackets is a maximum of 48” o.c. between mounting brackets (staggered)
and is secured using 5/16” diameter corrosive-resistant steel lag bolts. A minimum of 2½” of penetration (embedment)
per lag bolt is required, which will resist all stated loads above – including wind shear. Per NDS Section 12.1.4,
clearance holes - equal to the diameter of the shank - need to be bored into a primary framing member for the
full-length of the threaded portion of the bolt to avoid splitting of the framing member.
Regards,
Ihor Bojcun, PE
Structural Engineer - Trinity Solar
April 15, 2022
Trinity Solar No.
2022-02-670740