Ouimet, Diane- EL REVNorthampton, MA
212 Main St.
Northampton, MA 01060
31 Nutting Avenue
Florence, MA 01062
MA License No. 56687
RE: OUIMET, DIANE L
Trinity Solar | 4 Open Square Way, Suite 410 | Holyoke, MA | (413) 203-9088
October 27, 2023
Trinity Solar No.
2023-06-895286
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 2x8 at 24 o.c.; existing rafter span= 19' 0" supported by a load bearing wall with an existing 11' 4"
long triple 2x10 header in basement supporting the wall. Load wall and header limits rafter span to 10'; (horizontal projection)
Conventional roof framing at R3 is 2x6 at 24 o.c.; existing rafter span= 11' 6"; (horizontal projection)
2.Roof Loading:
• 3.0psf dead load (pounds per square foot - PV panels, mounting rails & hardware)
• 6.3psf - existing roof loads (2.3 psf - 2x8 framing, 1.5psf roof sheathing, 2.5 psf shingles)
• 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 modification at R1 basement header - existing triple 2x10 header to be "sistered" with (2) new 2x10s extending the full length
of the existing header and terminated before the existing header support connections. Sisters to use (2) 10d nails, one top and one bottom
(staggered) at 8" o.c the length of the sister rafter and (6) 10d nails at each end.
3. Existing roof modification at R3 - provide 2x4 (@16" o.c.) "knee wall" reinforcing to limit the maximum span of the existing rafter to 10'-
2". Locate bottom of "knee wall" within one foot of existing bearing wall below. Alternatively, existing roof rafters may be "sistered" with the
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. Typical sister nailing
consists of 10d nails top and bottom at 12" o.c. Within overlap, same nailing at 6"o.c.
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