FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
WWW.APAWOOD.ORG | 1
System Report
Use of Wood Structural Panels for Energy-Heel Trusses 1. BASIS OF
THE SYSTEM REPORT:
2012 International Residential Code (IRC): Sections R104.11
Alternative materia ls, design and methods of construc-
tion and equipment, R301.1.3 Engineered design, R602.3.5 Braced
wall panel uplift load path, R602.10.2.1 Braced
wall panel uplift load path, R602.10.8.2 Connections to roof
framing, R604.1 Identification and grade, and R802.11.1
Uplift resistance, and Tables R301.2(2), R301.2(3), and
R802.11
2009 International Residential Code (IRC): Sections R104.11
Alternative materials, design and methods of construc-
tion and equipment, R301.1.3 Engineered design, R604.1
Identification and grade, and R802.11.1 Uplift resistance,
and Tables R301.2(2), R301.2(3), and R802.11
ANSI/AWC WFCM-2012, Wood Frame Construction Manual for One-
and Two-Family Dwellings
US DOC PS 1-09, Structural Plywood
US DOC PS 2-10, Performance Standard for Wood-Based
Structural-Use Panels
NAHB Research Center reports dated August 8, 2011, February
15, 2012, and December 26, 2012
2. SYSTEM DESCRIPTION
As demand grows for energy efficiency in new structures,
ceiling insulation depth is often increased. This has
resulted
in a change in the way roof trusses are constructed. With
traditional rafters or trusses, the depth of attic insulation
is typically reduced above the wall top plates due to the narrow
space between the top plates and the roof sheathing
above. Further compromising this reduced space is the use of
ventilation baffles to maintain the required airflow into
the attic area from the eaves of the house. In addition,
compression of batt insulation at the eaves reduces the
R-value
of the insulation, leading to increased heating and cooling costs.
Recognizing these inefficiencies, the 2012 and 2009
International Energy Conservation Code (IECC) Section R402.2.1
allows for the prescriptive insulation level of the
attic to be reduced when energy-heel trusses are used.
For compliance with the IECC, trusses are increasingly being
constructed as energy-heel or raised-heel trusses, as
shown in Figure 1. Designed with a small vertical truss element at
the bearing locations of the truss, energy-heel trusses
provide sufficient space for full-depth insulation without
compromising the effectiveness of the attic ventilation or
the
insulation R-value. When properly installed, these vertical truss
elements are in alignment with the exterior surface of
the wall framing elements. However, the increased distance between
the roof sheathing and the top plates of the wall
complicates the required lateral support for these trusses. For
conventional trusses, horizontal 2x4 or 2x6 blocking is
used between the trusses to provide lateral support.
SR-103 MARCH 2014
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
WWW.APAWOOD.ORG | 2
When the distance from the bottom of the roof sheath-
ing to the top of the top wall plate is greater than
15-1/4 inches (2012 IRC Section R602.10.8.2(3) or
2009 IRC Section R602.10.6.2), a standard single 2x4
or 2x6 is insufficient to provide the required lateral
support. While the IRC has examples of 2x blocking
methods for energy-heel trusses, the alignment of the
truss heel with the outside surface of the wall framing
provides an opportunity for the use of wood structural
panel wall sheathing to resist lateral loads without
additional blocking.
In addition to the lateral loads acting on the trusses,
wind uplift loads must also be resisted by the struc-
tural system, as required in the 2012 IRC Sections
R602.1.5 and R602.10.2.1 (2009 IRC Section
R602.10.1.2). Just as wood structural panels can be
designed to resist both wind uplift and lateral loads
when used as shear walls and bracing panels, as shown
in APA System Report SR-101, Design for Combined
Shear and Uplift from Wind (APA Form SR-101,
www.apawood.org/publications), continuous wood structural panel
wall sheathing can be used to resist the wind
uplift and lateral loads acting at the truss connection as well.
This APA System Report was developed for the designer
to prescriptively meet the lateral load and wind uplift load
requirements of the IRC with energy-heel trusses of 15-1/4
to 24 inches in depth using wood structural panel wall
sheathing.
2.1 Scope
This report is intended for structures that are subjected to basic
wind speed of 110 mph or less and a wind exposure
category of B or C. It is also applicable to Seismic Design
Category A, B, or C for detached one- and two-family dwell-
ings or Seismic Design Category A or B for townhouses in accordance
with Section R301.2.2 of the 2012 IRC. For other
wind or seismic cases, the structures shall comply with the
pertinent provisions of the IRC or IBC.
Insulation
Energy-heel truss height
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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3. METHODOLOGY
Structures must meet all of the following conditions before using
the method prescribed in this report:
a. The building shall be designed in accordance with the 2012 or
2009 IRC;
b. Other sheathing methods covered by the IRC besides CS-WSP
are not applicable;
c. The trusses must be raised-heel trusses with a depth
between 15-1/4 and 24 inches;
d. The outside edge of the raised heel of the truss shall be in
alignment with the outside surface of the wall
framing below;
e. The aspect ratio (L/S) of the roof must be between 1/2:1
and 2:1 or greater;
f. Roof slope must be between 0:12 and 12:12;
g. Top-story stud wall height shall be 9 feet or less;
h. Mean roof height shall be 33 feet or less;
i. Roof span (S) shall be 36 feet or less;
j. Wall length (L) shall be 18 feet or longer;
k. Roof overhang shall be 24 inches or less;
l. Roof eave-to-ridge height shall be 15 feet or less;
m. Interior finish of exterior walls shall be as required in
the 2012 or 2009 IRC;
n. Wood structural panel sheathing shall be a minimum of 7/16
Performance Category with a Span Rating of 24/16.
3.1 Sheathing Installation
Wood structural panel sheathing, used as Method CS-WSP wall
bracing in accordance with the 2012 or 2009 IRC
Sections R602.10 through R602.12, shall be used to anchor the heels
of the energy-heel trusses. The uplift require-
ments of the 2012 IRC Sections R602.3.5 and R802.11 (2009 IRC
Sections R602.10.1.2.1 and R802.11) as well as the
wind-bracing attachment requirements of the 2012 IRC Section
R602.10.8.2 (2009 IRC Section R602.10.6.2) shall be
deemed to be satisfied by simply overlapping wood structural panel
sheathing over the truss heel with connection
in accordance with Figure 2 and wall anchor bolt installation in
accordance with Figure 3 and Tables 1 through 3 of
this report.
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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(7) 8d common nails (2-1/2" x 0.131") at each 24" raised-heel
truss
2 4 "
A 15-1/4-INCH AND 24-INCH ENERGY-HEEL TRUSS ATTACHMENT USING
WOOD STRUCTURAL PANEL SHEATHING
(5) 8d common nails (2-1/2" x 0.131") at each 15-1/4" raised-heel
truss
1 5
- 1
Wood structural panel sheathing
Trusses attached to top plate with (2) 16d (3-1/2" x 0.135") toe
nails (not shown for clarity)
Sheathing to top plate with 8d common nails (2-1/2" x 0.131") at 4"
o.c. (typical)
24-inch Raised-Heel Truss 15-1/4-inch Raised-Heel Truss
Sheathing attached to panel vertical edges and field, 8d common
nails (2-1/2" x 0.131") at 6" o.c. and 12" o.c. respectively.
Sheathing attached to top plate with 8d common nails (2-1/2" x
0.131") at 4" o.c. Normal panel nailing not shown for
clarity.
2 rows of 8d nails at min. 4" o.c. staggered
(1) 8d nail each bottom chord
2 rows of 8d nails at min. 4" o.c. staggered
(1) 8d nail each bottom chord
Wall length (ft) = L
Roof trusses (A maximum roof overhang of 24 inches outside of the
truss span is permitted)
T r u s
s s p a
n
( f t )
=
FIGURE 3
DEFINITION OF TERMS FOR TABLES 1 THROUGH 3 (PLAN VIEW OF ROOF
FRAMING MEMBERS)
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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TABLE 1
L/S ≥ 2:1 – unadjuSted anchor BoLt Spacing (incheS) for Wood
StructuraL paneL Sheathing
overLapping 15-1/4- to 24-inch energy-heeL roof truSSeS to provide
Shear and Wind upLift ()(b)()()
r S ()
r S ()
12 42 42 36 42 36 36 36 36
18 36 36 36 36 36 36 36 36
24 36 36 36 36 36 36 32 36
28 36 36 36 36 36 36 32 32
32 36 36 36 36 32 36 24 32
36 36 36 36 36 32 36 24 32
(a) Anchor bolts shall be ½-inch-diameter or larger with 3- x 3- x
0.229-inch square-plate washers spaced as shown in the table above.
See Section 3.5.1 for optional anchor bolt spacing
adjustment.
(b) See Figure 3 for wall configuration.
(c) Wall shall be installed and attached in accordance with Figure
2. Conditions beyond assumptions listed in Section 3 are outside
the scope of this report.
(d) Interpolation shall be permitted, but extrapolation shall not
be permitted.
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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TABLE 2
2:1 > L/S ≥ 1:1 – unadjuSted anchor BoLt Spacing (incheS) for
Wood StructuraL paneL Sheathing
overLapping 15-1/4- to 24-inch energy-heeL roof truSSeS to provide
Shear and Wind upLift ()(b)()()()
r S ()
r S ()
12 42 42 36 42 36 36 36 36
18 36 36 36 36 36 36 36 36
24 36 36 36 36 36 36 32 36
28 36 36 36 36 36 36 32 32
32 36 36 36 36 32 36 24 32
36 36 36 36 36 32 32 NA NA
(a) Anchor bolts shall be ½-inch-diameter or larger with 3- x 3- x
0.229-inch square-plate washers spaced as shown in the table above.
See Section 3.5.1 for optional anchor bolt spacing
adjustment.
(b) See Figure 3 for wall configuration.
(c) Wall shall be installed and at tached in accordance with Figure
2. Conditions beyond assumptions listed in Section 3 are outside
the scope of this report.
(d) Interpolation shall be permitted, but extrapolation shall not
be permitted.
(e) NA = Not applicable and engineered design required.
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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TABLE 3
1:1 > L/S ≥ 1/2:1 – unadjuSted anchor BoLt Spacing (incheS) for
Wood StructuraL paneL Sheathing
overLapping 15-1/4- to 24-inch energy-heeL roof truSSeS to provide
Shear and Wind upLift ()(b)()()()
r S ()
r S ()
12 32 24 24 19.2 24 19.2 24 19.2
18 24 19.2 24 19.2 24 19.2 24 NA
24 24 19.2 24 19.2 24 19.2 NA NA
28 24 19.2 24 19.2 24 NA NA NA
32 24 19.2 24 19.2 24 NA NA NA
36 24 19.2 24 NA NA NA NA NA
(a) Anchor bolts shall be ½-inch-diameter or larger with 3- x 3- x
0.229-inch square-plate washers spaced as shown in the table above.
See Section 3.5.1 for optional anchor bolt spacing
adjustment.
(b) See Figure 3 for wall configuration.
(c) Wall shall be installed and attached in accordance with Figure
2. Conditions beyond assumptions listed in Section 3 are outside
the scope of this report.
(d) Interpolation shall be permitted, but extrapolation shall not
be permitted.
(e) NA = Not applicable and engineered design required.
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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3.2 Fastener Attachments
Wood structural panel sheathing shall be attached to framing
with 8d common nails (0.131 inch x 2-1/2 inches) at
6 inches o.c. at the panel sides and bottom edges. Wood structural
panel sheathing shall be attached at the top plate
with 8d common nails at 4 inches o.c. Note that this is a deviation
from common practice for wood structural panel
bracing panels, which are typically nailed at 6 inches o.c. around
the perimeter. All panel sheathing field nailing shall
be 8d common nails at 12 inches o.c., except at the raised heel of
trusses, as shown in Figure 2.
Attachment at the raised heel of the trusses shall be with 8d
common nails. A single nail shal l be placed through the
panel into the bottom chord of the truss. The additional nails
required shall be placed in the raised heel of the truss
in two rows, with the nails staggered and spaced at 4 inches o.c.
in each row. The 15-1/4-inch energy-heel truss shall
require a total of 5 nails into the heel of each truss and the
24-inch truss shall require a total of 7 nails in each heel.
For trusses between 15-1/4 and 24 inches, interpolation shall be
permitted for determining the minimum number of
nails required. See Figure 2.
3.3 Design Properties
Wood structural panel sheathing shal l meet the requirements
of PS 1 or PS 2 with the design properties as specified
in Panel Design Specification (APA Form D510,
www.apawood.org/publications). The wood structural panels are
per-
mitted for use in conjunction with 15-1/4- to 24-inch energy-heel
trusses in compliance with the 2012 or 2009 IRC
Method CS-WSP bracing and wind uplift attachment requirements when
the requirements of Tables 1 through 3 of
this report are met.
Heel heights on energy-heel trusses along with corresponding anchor
bolt requirements and sheathing attachment
requirements (other than those described in this report) shall be
permitted to be designed through engineering analysis.
See APA System Report SR-101, Design for Combined Shear and Uplift
from Wind (APA Form SR-101, www.apawood.org/
publications) for more information.
3.5 Use of Design Tables
The following steps illustrate the use of design tables provided in
this report:
Check the building for compliance with all conditions listed
in Section 3 of this report.
Determine the aspect ratio of the roof using Figure 3.
From the aspect ratio (L/S) determined above, go to the
appropriate table:
L/S ≥ 2:1, use Table 1
2:1 > L/S ≥ 1:1, use Table 2
1:1 > L/S ≥ 1/2:1, use Table 3
Enter the appropriate table with the wind speed, exposure
classification, roof pitch, and roof span. If a number is
provided in the corresponding table cell, overlapping the
energy-heel truss with the sheathing in accordance with
Section 3.1 and attaching it in accordance with Section 3.2 will
meet wind uplift loads required in the 2012 or 2009
IRC Sections R802.11, as well as the lateral loads required by the
load path. The number provided in the cell is the
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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3.5.1 Optional Step
The above calculation presupposes that each foot of the wall has
both the lateral load component and the uplift com-
ponent. In most cases, especially in cases limited to low seismic
areas, the wall bracing is only a fraction of the braced
wall line. In a given braced wall line segment, a wall line w ith a
continuous bottom plate – that is, one that is not
interrupted by door openings or bump-outs – a simple calculation
can be used to adjust the unadjusted anchor bolt
spacing up to the maximum permitted by the 2012 or 2009 IRC (60
inches o.c. maximum for low seismic areas). The
calculation is as follows:
Go through the steps in Section 3.4 above to determine if
overlapping the energy-heel truss with the wood structural
panel wall sheathing is acceptable. If so, record the anchor bolt
spacing from Table 1, 2 or 3.
Determine the ratio of the uninterrupted braced wall line
segment length over the actual amount of bracing in that
segment.
Multiply the maximum anchor bolt spacing by this ratio,
remembering that the adjusted anchor bolt spacing cannot
exceed 60 inches.
Optional Step Example:
Assuming an unadjusted anchor bolt spacing of 32 inches o.c.
is specified in Table 2.
The braced wall line length in question is 23 feet, measured
between door openings or bump-outs (uninterrupted
bottom plate).
Only 6 feet of this braced wall line is required to be
braced.
The ratio of the braced wall line length (23 feet) over the
required wall bracing length (6 feet) is 23/6 = 3.83.
The adjusted anchor bolt spacing is 32 x 3.83 = 122.6
inches.
Use the code required maximum anchor bolt spacing of 60
inches o.c.
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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4. LIMITATIONS
a. Buildings shall meet all conditions specified in Section 3
of this report.
b. Energy-heel trusses shall be l imited to 15-1/4 to 24 inches in
depth.
c. Wood structural panel sheathing shall be designed and
installed in accordance with Sections 3.1 and 3.2
of this report.
d. Wood structural panel sheathing for use in this
application shall meet PS 1 or PS 2 requirements with the
design properties as specified in Panel Design
Specification (APA Form D510,
www.apawood.org/publications).
e. Wood structural panel sheathing shall be of sufficient
capacity to resist applied wind loads. SeeTechnical Topics:
Wind Resistance of Wood Structural Panel Sheathed Wall (APA
Form TT-110, www.apawood.org/publications).
f. This report is subject to periodic review. The latest copy of
this report is available for free download at
FORM NO. SR-103 © 2014 APA – THE ENGINEERED WOOD ASSOCIATION
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APPENDIX A
Design Example
Given: A building is designed with a roof length (L) of 88 feet and
a truss span (S) of 32 feet. 18-inch energy-heel trusses
will be used. Wood structural panel sheathing meeting PS 1 or PS 2
requirements is designed for blocking the trusses
to resist lateral and wind uplift loads. What is the anchor bolt
spacing that will meet the 2012 IRC requirements?
Other information:
Solution steps:
a. The building meets all of the requirements of Sections 3 and
4.
b. The L/S ratio = 88/32 = 2.75. Use Table 1 for L/S >
2:1.
c. Enter Table 1 with Exposure B, 100 mph, roof slope < 5:12,
and roof span (S) 32 feet.
d. The anchor bolt spacing provided in the corresponding table cell
can be used to design blocking for the
trusses to resist lateral and wind uplift loads. In this case, the
anchor bolt spacing is 36 inches. Note that
this is the unadjusted anchor bolt spacing that may be used to
anchor the braced wall panels to the founda-
tion at the first story.
e. The permitted anchor bolt spacing may be adjusted for each
un-interrupted braced wall line segment as
described in Section 3.5.1.
Use of Wood Structural Panels for Energy-Heel Trusses
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Form No. SR-103/Issued March 2014/0100