Martin, Sophie- EL REVNorthampton, MA
212 Main St.
Northampton, MA 01060
58 Autumn Drive
Northampton, MA 01062
Trinity Solar | 4 Open Square Way, Suite 410 | Holyoke, MA | (413) 203-9088
MA License No. 56687
RE: MARTIN, BRUCE S; MARTIN, SOPIE H
October 11, 2021
Trinity Solar No.
2021-08-610797
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 is 2x6 at 16 o.c.; existing rafter span= 12' 0"; (horizontal projection)
2.Roof Loading:
• 4.33psf dead load (pounds per square foot - PV panels, mounting rails & hardware)
• 5.7 psf - 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 equivalent to 23.09psf wind pressure
3. Existing roof modification - provide 2x4 (@16" o.c.) "knee wall" reinforcing to limit the maximum span of the
existing rafter to 10'-10". Locate bottom of "knee wall" within one foot of existing bearing wall below. Where no existing
bearing wall exists, provide triple 2x6 header spanning 6'-0" between header support locations to support the 4-5 rafters,
as required.
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 11.1.4,
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