Bushey, Matthew - UPDATED STRUCTURAL LETTERNorthampton, MA
212 Main St.
Northampton, MA 01060
984 Park Hill Road
Northampton, MA 01062
RE: BUSHEY, MATTHEW R
Trinity Solar | 4 Open Square Way, Suite 410 | Holyoke, MA | (413) 203-9088
Regards,
Ihor Bojcun, PE
Structural Engineer - Trinity Solar
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.
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 - "Sister" existing rafters with new 2x6 rafters extending the full length of the existing
rafters and terminated before the existing rafter support connection. Alternatively, provide 2x4 (@16" o.c.) "knee wall"
reinforcing to limit the maximum span of the existing rafter to 10'-8". Locate bottom of "knee wall" within one foot of
existing bearing wall below.
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.
July 7, 2022
Trinity Solar No.
2022-01-664504
Existing roof framing at R1 and R3:
Conventional roof framing is 2x6 at 16 o.c.; existing rafter span= 12' 0"; (horizontal projection)