Structural Letter - Ashton, Joseph - Leeds, MA - 10421531___________________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
To: RGS Energy
420 Woodland Ave. Unit A
Bloomfield, CT. 06002
Subject: Certification Letter
Ashton Residence
1 Bernache St
Leeds, MA. 01053
To Whom It May Concern,
The scope of this report is strictly limited to an evaluation of the fastener attachment, underlying framing and supporting
structure only. The attachment's to the existing structure are required to be in a staggered pattern to ensure proper distribution
of loading. All panels, racking and hardware shall be installed per manufacturer specifications and within specified design
limitations. All waterproofing shall be provided by the manufacturer. Domus Structural Engineering assumes no responsibility for
misuse or improper installation of the solar PV panels or racking.
March 18, 2019
The roof structure of (Roof 1) consists of composition shingle on roof plywood that is supported by 2x8 rafters @ 24"o.c., paired
with nominal 2x8 ceiling joists @ 24"o.c.. The rafters are suported by veritcal struts which transfer gravity loads to the ceiling
joists below. The rafters have a max projected horizontal span of 8'‐6", with a slope of 37 degrees. The rafters are connected at
the ridge to a ridge board and are supported at the eave by a load bearing wall.
The roof structure of (Roof 2) consists of composition shingle on roof plywood that is supported by nominal 2x6 rafters @ 24"o.c.
paired with 2x6 ceiling joists @ 48"o.c.. The rafters have a max projected horizontal span of 13'‐0", with a slope of 16 degrees.
The rafters are connected at the ridge to a ridge board and are supported at the eave by a load bearing wall.
The existing roof framing system of (Roof 1) is judged to be adequate to withstand the loading imposed by the installation of the
solar panels. No reinforcement is necessary.
The existing roof framing system of (Roof 2) is judged to be inadequate to withstand the loading imposed by the installation of the
solar panels. Structural reinforcement is required. Sister upgrade is required for (Roof 2) on all rafters that directly support solar
PV. Stitch new 2x8 DF#2 (min) to existing member with Simpson SDW 22300 screws @ 16''o.c. or 10d nails @ 6''o.c.. Lap as
needed with 4'‐0'' lap per attached detail.
The spacing of the solar standoffs should be kept at 48" o.c. for landscape and 48" o.c. for portrait orientation, with a staggered
pattern to ensure proper distribution of loads.
A jobsite observation of the condition of the existing framing system was performed by an audit team of RGS Energy as a request
from Domus Structural Engineering. All review is based on these observations and the design criteria listed below and only
deemed valid if provided information is true and accurate.
On the above referenced project, the roof structural framing has been reviewed for additional loading due to the installation of
the solar PV addition to the roof. The structural review only applies to the section of the roof that is directly supporting the solar
PV system and its supporting elements. The observed roof framing is described below. If field conditions differ, contractor to
notify engineer prior to starting construction.
Ashton Residence, Leeds, MA 1
___________________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
Design Criteria:
● Applicable Codes = Massachusetts Residential Code, 9th Edition, ASCE 7‐10
● Roof Dead Load = 12 psf (Roof 1) ‐‐ 9 psf (Roof 2)
● Roof Live Load = 20 psf
● Wind Speed = 117 mph (Vult), Exposure B, Risk Category II
●
● Attachments: 1 ‐ 5/16" dia. lag screw with 2.5 inch min embedment depth, at spacing shown above.
Sincerely,
John Calvert, P.E.
Project Engineer
Please contact me with any further questions or concerns regarding this project.
Note: Seismic check is not required since Ss<.4g and Seismic Design Category (SDC) < B
Ground Snow Load = 40 psf ‐ Roof Snow Load = 35 psf
Ashton Residence, Leeds, MA 2
____________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
Address: 1 Bernache St, Leeds, MA. 01053
Exposure: B
Wind Speed: 117 mph
Risk Category: II
Aerial Image
Ashton Residence, Leeds, MA 3
____________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
40 psf
(ASCE7 - Eq 7-1)
1 (ASCE7 - Table 7-2)
1 (ASCE7 - Table 7-3)
1
40.0 psf
(ASCE7 - Eq 7-2)
1
40.0 psf
4.03 psf
3.2 psf
4.00 ft
2.75 ft
11.00 sft
35 lb
4.00
2.00
1.52
4.00 (Enclosed Attic)
0.48
12.0 psf
15.0 psf
4.00
2.00
2.30
0.00 (Ceiling Not Vaulted)
0.70
9.0 psf
9.36
PV Dead Load = 3.22 psf (Per RGS Energy)
DL Adjusted to 37 Degree Slope
Point Loads of Standoffs
DL Adjusted to 16 Degree Slope
Miscellaneous
Vaulted Ceiling
Miscellaneous
Total Roof DL (Roof 2)
Total Roof DL (Roof 1)
Roof Dead Load (Roof 2)
Composition Shingle
Roof Live Load = 20 psf
Roof Plywood
Roof Dead Load (Roof 1)
Composition Shingle
Note: Roof live load is removed in area's covered by PV array.
Roof Snow Load Calculations
pg = Ground Snow Load =
Ce = Exposure Factor =
pf = 0.7 Ce Ct I pg
Ct = Thermal Factor =
I = Importance Factor =
Cs = Slope Factor =
Standoff Tributary Area =
ps = Cspf
ps = Sloped Roof Snow Load =
pf = Flat Roof Snow Load =
DL Adjusted to 37 Degree Slope
Gravity Loading
PV System Weight
Weight of PV System (Per RGS Energy)
X Standoff Spacing =
Y Standoff Spacing =
Note: PV standoffs are staggered to ensure proper distribution of loading
Roof Plywood
Vaulted Ceiling
2x8 Rafters @ 24"o.c.
Sistered Rafters
Ashton Residence, Leeds, MA 4
___________________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
117 mph
B
Hip/Gable
16 degrees
25 ft
19.3 ft
(Eq. 30.3-1)
0.7 (Table 30.3-1)
1 (Fig. 26.8-1)
0.85 (Table 26.6-1)
117 mph (Fig. 26.5-1A)
II (Table 1.5-1)
qh = 20.85
12.51
Zone 1 Zone 2 Zone 3 Positive
GCp = -0.84 -1.39 -2.23 0.38 (Fig. 30.4-1)
Uplift Pressure = -10.48 psf -17.39 psf -27.87 psf 10.0 psf (Minimum)
X Standoff Spacing = 4.00 4.00 2.67
Y Standoff Spacing = 2.75 2.75 2.75
Tributary Area = 11.00 11.00 7.33
Footing Uplift = -115 lb -191 lb -204 lb
Zone 1 Zone 2 Zone 3 Positive
GCp = -0.84 -1.39 -2.23 0.38 (Fig. 30.4-1)
Uplift Pressure = -10.48 psf -17.39 psf -27.87 psf 10.0 psf (Minimum)
X Standoff Spacing = 4.00 4.00 2.67
Y Standoff Spacing = 1.67 1.67 1.67
Tributary Area = 6.68 6.68 4.45
Footing Uplift = -70 lb -116 lb -124 lb
-204 lb
450 lb
Therefore, OK
Fastener =1 - 5/16" dia. lag
Number of Fasteners = 1
Embedment Depth = 2.5
Pullout Capacity Per Inch = 250 lb
Fastener Capacity = 625 lb
w/ F.S. of 1.5 & DOL of 1.6= 667 lb
Therefore, OK
Input Variables
Wind Speed
Effective Wind Area
Design Wind Pressure Calculations
Roof Shape
Standoff Uplift Calculations-Portrait
Mean Roof Height
Roof Slope
667.2 lb capacity > 204 lb demand
0.6 * qh =
Standoff Uplift Calculations-Landscape
Wind Calculations
Maximum Design Uplift =
Standoff Uplift Capacity =
450 lb capacity > 204 lb demand
Fastener Capacity Check
Standoff Uplift Check
Kz (Exposure Coefficient) =
Kzt (topographic factor) =
Kd (Wind Directionality Factor) =
V (Design Wind Speed) =
Risk Category =
qh = 0.00256 * Kz * Kzt * Kd * V^2
Wind Pressure P = qh*G*Cn
Exposure Category
Per ASCE 7‐10 Components and Cladding
Ashton Residence, Leeds, MA 5
____________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
Framing Information & Site Specific Pictures
Ashton Residence, Leeds, MA 6
____________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
DLroof =9 psf
SLroof =35 psf
PV = 4 psf
Name Size Grade Base Depth E (psi) I EI (lb/in.2)*(in.4)
(E) Rafter 2x6 DF2 1.50'' 5.50'' 1600000 20.80 in^4 33275000
(N) Sister 2x8 DF2 1.50'' 7.25'' 1600000 47.63 in^4 76215625
33275000
109490625
DLroof = 9 psf x 0.304 = 2.74 psf
SLroof = 35 psf x 0.304 = 10.64 psf
PV = 4 psf x 0.304 = 1.23 psf
76215625
109490625
DLroof = 9 psf x 0.696 = 6.26 psf
SLroof =35 psf x 0.696 = 24.36 psf
PV = 4 psf x 0.696 = 2.81 psf
Member Stiffness Check
Loading Summary
Methodology: As new and existing members are sistered and joined together, they will deflect the same
amount. The following calculations show how loading is distributed between the two members.
Member Stiffness
Loading to Existing Member
Loading to (E) Member =
Based on relative member stiffness, 69.6 percent of total load goes to (E) member
=EL(E)
EL(E) + EL(N)= 30.4%
Loading to (N) Member = EL(N)= = 69.6%EL(N) + EL(E)
Based on relative member stiffness, 30.4 percent of total load goes to (E) member
Loading to New Member
Ashton Residence, Leeds, MA 7
___________________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
(Roof 1)PASS
Dead Load 15.0 psf
PV Load 4.0 psf
Snow Load 35.0 psf
Governing Load Combo = DL + SL
Total Load 54.1 psf
Fb (psi) = f'b x Cd x Cf x Cr (NDS Table 4.3.1)
900 x 1.15 x 1.2 x 1.15
Allowed Bending Stress = 1428.3 psi
(wL^2) / 8
= 976.4137 ft#
= 11716.96 in#
Actual Bending Stress = (Maximum Moment) / S
= 891.7 psi
L/180 (E = 1600000 psi Per NDS)
= 0.566 in
Deflection Criteria Based on =
(5*w*L^4) / (384*E*I)
=
= L/611 > L/180 Therefore OK
Allowed Deflection (Live Load) =L/240
0.425 in
(5*w*L^4) / (384*E*I)
L/945 > L/240 Therefore OK
Member Area = Fv (psi) = 180 psi (NDS Table 4A)
Allowed Shear = Fv * A = Max Shear (V) = w * L / 2 = 459 lb
Check Bending Stress
(True Dimensions)
Simple Span
0.167 in
0.108 in
Member Properties
Member Size
2x8
S (in^3)
13.14 DF#2
Member Spacing
@ 24"o.c.
Maximum Moment =
Check Deflection
I (in^4)
47.63
Lumber Sp/Gr
Actual Deflection (Live Load) =
Allowed Deflection (Total Load) =
Actual Deflection (Total Load) =
Allowed > Actual -- 62.5% Stressed -- Therefore, OK
1958 lb
Allowed > Actual -- 23.5% Stressed -- Therefore, OK
10.9 in^2
Check Shear
w = 108 plf
2x8 Rafters @ 24"o.c.
Member Span = 8' - 6"
Framing Check
Ashton Residence, Leeds, MA 8
___________________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
(Roof 2)PASS - With Framing Upgrades
Dead Load 2.7 psf
PV Load 1.2 psf
Snow Load 10.6 psf
Governing Load Combo = DL + LL
Total Load 24.0 psf
Fb (psi) = f'b x Cd x Cf x Cr (NDS Table 4.3.1)
900 x 1.25 x 1.3 x 1.15
Allowed Bending Stress = 1681.8 psi
(wL^2) / 8
= 1012.33 ft#
= 12147.96 in#
Actual Bending Stress = (Maximum Moment) / S
= 1606.4 psi
L/120 (E = 1600000 psi Per NDS)
= 1.3 in
Deflection Criteria Based on =
(5*w*L^4) / (384*E*I)
=
= L/169 > L/120 Therefore OK
Allowed Deflection (Live Load) =L/180
0.866 in
(5*w*L^4) / (384*E*I)
L/202 > L/180 Therefore OK
Member Area = Fv (psi) = 180 psi (NDS Table 4A)
Allowed Shear = Fv * A = Max Shear (V) = w * L / 2 = 311 lb
Framing Check
Simple Span
0.773 in
0.926 in
(True Dimensions)
1485 lb
Allowed > Actual -- 21% Stressed -- Therefore, OK
Check Bending Stress
Maximum Moment =
Allowed > Actual - 95.6% Stressed -- Therefore, OK
Check Deflection
Allowed Deflection (Total Load) =
Actual Deflection (Total Load) =
Actual Deflection (Live Load) =
w = 48 plf
2x6 Rafters @ 24"o.c.
Member Span = 13' - 0"
Member Properties - Based on Upgraded Section
Member Size S (in^3) I (in^4) Lumber Sp/Gr Member Spacing
2x6 7.56 20.80 DF#2 @ 24"o.c.
Check Shear
8.3 in^2
Ashton Residence, Leeds, MA 9
___________________________________________________________________________________________
Domus Structural Engineering, LLC
P.O. Box 6986
Broomfield, CO 80021
530-864-7055
Domusstructural@gmail.com
--(Roof 1)PASS
Dead Load 6.3 psf
PV Load 2.8 psf
Snow Load 24.4 psf
Governing Load Combo = DL + SL
Total Load 33.4 psf
Fb (psi) = f'b x Cd x Cf x Cr (NDS Table 4.3.1)
900 x 1.15 x 1.2 x 1.15
Allowed Bending Stress = 1428.3 psi
(wL^2) / 8
= 603.9132 ft#
= 7246.958 in#
Actual Bending Stress = (Maximum Moment) / S
= 551.5 psi
L/120 (E = 1700000 psi Per NDS)
= 0.85 in
Deflection Criteria Based on =
(5*w*L^4) / (384*E*I)
=
= L/981 > L/120 Therefore OK
Allowed Deflection (Live Load) =L/180
0.566 in
(5*w*L^4) / (384*E*I)
L/1343 > L/180 Therefore OK
Member Area = Fv (psi) = 180 psi (NDS Table 4A)
Allowed Shear = Fv * A = Max Shear (V) = w * L / 2 = 284 lb
Framing Check (N) 2x8 Sister
Simple Span
0.104 in
Maximum Moment =
Allowed > Actual -- 38.7% Stressed -- Therefore, OK
Check Deflection
Allowed Deflection (Total Load) =
Actual Deflection (Total Load) =
w = 67 plf
2x8 Rafters @ 24"o.c.
Member Span = 8' - 6"
Member Properties
Member Size S (in^3) I (in^4) Lumber Sp/Gr Member Spacing
DF#2 @ 24"o.c.2x8 13.14 47.63
(True Dimensions)
Check Bending Stress
Actual Deflection (Live Load) =
Check Shear
10.9 in^2
1958 lb
Allowed > Actual -- 14.6% Stressed -- Therefore, OK
0.076 in
Ashton Residence, Leeds, MA 10