High-R Walls for New 

Construction Structural 

Performance: Integrated Rim 

Header Testing 

A. DeRenzis, V. Kochkin, and J. Wiehagen

NAHB Research Center

January 2013
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iii

High-R Walls for New Construction 

Structural Performance: Integrated Rim Header Testing

Prepared for: 

The National Renewable Energy Laboratory 

On behalf of the U.S. Department of Energy’s Building America Program 

Office of Energy Efficiency and Renewable Energy 

15013 Denver West Parkway 

Golden, CO 80401 

NREL Contract No. DE-AC36-08GO28308 

Prepared by: 

A. DeRenzis, V. Kochkin, and J. Wiehagen

NAHB Research Center

400 Prince George’s Blvd. 

Upper Marlboro, MD 20774 

NREL Technical Monitor: Stacey Rothgeb 

Prepared under Subcontract No. KNDJ-0-40335-00 

January 2013 
iv

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v 

Contents

List of Figures ............................................................................................................................................ vi

List of Tables .............................................................................................................................................. vi

Definitions.................................................................................................................................................. vii

Executive Summary................................................................................................................................. viii

1 Problem Statement............................................................................................................................... 1

1.1 Introduction ..........................................................................................................................1

1.2 Background ..........................................................................................................................2

1.3 Relevance to Building America’s Goals ..............................................................................2

1.4 Cost Effectiveness ................................................................................................................2

1.5 Tradeoffs and Other Benefits ...............................................................................................2

2 Experiment ............................................................................................................................................ 4

2.1 Research Questions—Rim Header ......................................................................................4

2.2 Technical Approach—Rim Header ......................................................................................4

2.2.1 Specimen Construction ............................................................................................6

2.3 Measurements—Rim Header .............................................................................................13

2.3.1 Test Setup and Protocol .........................................................................................13

2.4 Equipment—Rim Header ...................................................................................................14

3 Analysis ............................................................................................................................................... 19

3.1 Analysis of Results ............................................................................................................19

3.1.1 Stage 1 Results .......................................................................................................19

3.1.2 Stage 2 Results .......................................................................................................19

3.1.3 Stage 3 Results .......................................................................................................23

3.1.4 Stage 4 Results .......................................................................................................27

3.2 Example Design Calculation ..............................................................................................27

4 Conclusions ........................................................................................................................................ 28

References................................................................................................................................................. 29

Appendix A ................................................................................................................................................ 30
vi 

List of Figures

Figure 1. Stage 1 specimen construction and test set-up...................................................................... 9

Figure 2. Lower portion of a typical Stage 2, 3 and 4 test specimen................................................... 11

Figure 3. Typical Stage 2 and 4 test specimen ...................................................................................... 12

Figure 4. Typical Stage 2 and 4 test set-up ............................................................................................ 15

Figure 5. Typical Stage 3 test set-up....................................................................................................... 16

Figure 6. Stage 1 test setup ..................................................................................................................... 17

Figure 7. Stage 2 test setup ..................................................................................................................... 18

Figure 8. Stage 1 test results ................................................................................................................... 19

Figure 9. Stage 2 rough opening top member midspan deflections (exterior face) .......................... 20

Figure 10. Stage 2 rough opening top member midspan deflections (interior face)......................... 20

Figure 11. Stage 2 average movement of joist hangers relative to rim header.................................. 21

Figure 12. Stage 2 bearing deformations of top plate (exterior edge)................................................. 22

Figure 13. Stage 2 bearing deformations of top plate (interior edge) ................................................. 22

Figure 14. Bearing deformations and simplified stress distribution at king stud-to-top plate 

interface............................................................................................................................................... 23

Figure 15. Stage 3 rough opening top member midspan deflections (exterior face) ........................ 24

Figure 16. Stage 3 rough opening top member midspan deflections (interior face)......................... 24

Figure 17. Stage 3 average movement of joist hangers relative to rim header.................................. 25

Figure 18. Stage 3 bearing deformations of top plate (exterior edge)................................................. 26

Figure 19. Stage 3 bearing deformations of top plate (interior edge) ................................................. 26

Unless otherwise indicated, all figures were created by NAHB.

List of Tables

Table 1. Individual Hanger Testing Matrix................................................................................................ 5

Table 2. Rim Header System Testing Matrix ............................................................................................ 5

Table 3. Individual Hanger Construction Materials ................................................................................. 7

Table 4. Rim Header System Testing Construction Materials................................................................ 7

Table 5. Nailing Schedule—Rim Header................................................................................................... 8

Table 6. Load Levels for Stage 2 Tests—Rim Header........................................................................... 13

Table 7. Load Levels for Stage 3 Tests—Rim Header........................................................................... 13

Unless otherwise indicated, all tables were created by NAHB.
vii 

Definitions

2 × 4 Nominal 2 in. wide by 4 in. depth framing lumber dimension

2 × 6 Nominal 2 in. wide by 6 in. depth framing lumber dimension

Advanced framing An optimized framing system to reduce extraneous framing members 

while maintaining structural integrity with the goals of increased 

thermal performance and lower cost

Cb Bearing area factor, used in design of wood structural members

Ci Incising factor for dimensional lumber, used in design of wood 

structural members

Cm Wet service factor, used in design of wood structural members

Ct Temperature factor, used in design of wood structural members

DL Dead load

Fcperp Reference compression design value perpendicular to grain

Fcperp ‘ Adjusted compression design value perpendicular to grain

High-R wall Reference to wall systems generally having an R-value of 1.5 to 2.5 

times that of current energy code requirements for a given climate zone

IRC International Residential Code

Joist hanger Steel hardware designed to provide attachment of floor joist to 

perpendicularly framed structural member

King stud Full height structural framing member adjacent to an opening that 

supports the structural rim header member above. 

L/360 Code specified deflection limit for structural members supporting live 

load only, expressed as a fraction of the span length, L. 

L/240 Code specified deflection limit for structural members supporting total 

design load, expressed as a fraction of the span length, L 

LL Live load

LMPT Linear motion position transducer

OSB Oriented strand board

Pg Ground snow load

plf Pounds per linear foot

psf Pounds per square foot

SPF Spruce-Pine-Fir—lumber species

TJI Joist Structural wood framing member having an I-shaped cross section, 

manufactured by Weyerhaeuser. 
viii

Executive Summary

The Building America Program takes two prominent approaches to construct higher R-value 

walls: larger dimension framing and exterior rigid foam insulation. These have had some 

success; however, for many production builders the cost of changing framing systems is high, so 

the changes have been slowly realized. Also, recent building code changes have raised some 

performance issues for exterior sheathing and raised heel trusses, for example, that indicates a 

need for continued performance testing of wall systems. Furthermore, some material use survey 

data have shown that often when builders are switching to 2 × 6 framing members, they 

commonly use of 16-in. o.c. spacing. The opportunity to (1) encourage the use of thicker framing 

systems for much higher R-value walls; (2) construct wall systems that optimize the framing use 

to reduce thermal breaks; and (3) extract opportunities to reduce costs, all remain high priorities 

for the Building America program, the NAHB Research Center Industry Partnership, and 

builders. Similarly for the use of exterior rigid sheathing, builders and researchers have 

investigated alternative bracing techniques to eliminate the use of wood structural sheathing in 

lieu of foam board sheathing. Structural characteristics, especially in the direction perpendicular 

to the sheathing, have been reevaluated for the building codes. These include pressure 

equalization issues across multiple layers of the wall system.

The combination of these issues, including limiting cost increases when switching to higher Rvalue wall systems, has prompted the need for structural testing and optimized wall framing 

designs. This report focuses primarily on laboratory testing that evaluates the structural 

performance of rim headers. This research and test activity will help to facilitate the designs of 

load-bearing wall systems that minimize or eliminate the use of traditional headers within the 

wall plane and considers dead and live loads as well as roof and floor loading. Overall goals are

to develop framing system designs based on 2 × 6 framing members that simplify and limit cost 

increases when builders and remodelers switch from traditional 2 × 4 framing methodologies.

The testing methodology presented here evaluates structural rim header designs over openings up 

to 6 ft wide and applicable to one- and two-story homes. Roof loading is also considered, 

including snow depths in cold climate zones. 

The integrated rim header system design successfully maintained window serviceability 

throughout typical residential service load levels from the floor, wall, and roof systems. No 

decrease in window operability was observed at any tested load levels, under either roof or floor 

loading. The rim header system also provided a continuous vertical load path for roof loading 

through the bearing walls above and into the rim member. Approximately 8% of the imposed 

roof load was transposed to the adjacent floor framing and joist hangers attached to the rim 

header. This load can easily be accounted for in the sizing of the joist hangers. 
1 

1 Problem Statement 

1.1 Introduction

The NAHB Research Center Building America industry team high-R wall system research 

focuses primarily on increasing the wall’s thermal performance and maintaining current 

constructability and affordability features. High-R wall system designs for residential 

construction have centered on reducing the framing factor of the wall system to allow more area 

for insulation materials. The ultimate goal is to promote options to substantially increase wall

insulation by cost-effectively upgrading from 2 × 4 to 2 × 6 advanced framing. 

Advanced framing techniques such as turn-stud corners and ladder blocking are the most 

common techniques for decreasing the framing factor, as they maintain the structural 

performance characteristics. More complex methods, such as the use of in-line (or stack) 

framing, facilitate 24-in. o.c. stud spacing. These advanced framing techniques are designed to 

reduce the lumber member count and the overall area of the wall that is made up of solid wood 

components (which have a much lower insulating value) by a factor of three or more. Although 

some of these techniques can apply to 2 × 4 framing, some (such as 24-in. o.c. stack framing) 

may require 2 × 6 framing members. 

The switch to 2 × 6 framing to encourage use of 24-in. o.c. stud spacing has been an important 

part of high performance wall system design. A review of lumber use data for home 

construction1 indicates that the switch to 2 × 6 appears to be increasing; however, advanced 

framing techniques do not appear to be implemented as the increase is primarily with 2 × 6, 16-

in. o.c. framing. The NAHB Research Center recognized this phenomenon, coupled with 

anecdotal evidence that some builders hesitate to switch to advanced 2 × 6 framing, and 

embarked on an effort to achieve a much higher level of optimization when switching to 

advanced framing designs. This effort was undertaken to minimize the cost increase in switching 

to advanced 2 × 6 framing and to increase the wall system’s energy performance level beyond 

new energy code requirements.

As part of the 2 × 6 advanced framing, framing might be reduced and insulation increased via an 

innovative rim header design that uses the rim joist member that is already present in a typical 

home as a structural member to support and transfer vertical loads around openings. This

eliminates the need for structural headers within the wall plane. When combined with 2 × 6 

framing, this advanced detail reduces the framing around openings without increasing the cost of 

framing materials. 

This report summarizes research and technical findings that support advanced framing methods 

to increase opportunities for high-R walls to be used as a much more common construction 

method. It focuses primarily on testing an integrated rim header system for gravity loading, 

which addresses vertical load path and serviceability limits. Integrated rim headers will reduce 

framing factors that degrade the wall system’s thermal performance. 

 

1 NAHB Research Center proprietary Builder Practices Survey based on data analyzed across multiple years for wall framing 

materials and spacing.
2 

1.2 Background

Research has been conducted into increasing wall insulation as a response to high performance

homes and stricter energy codes (NAHBRC 2009-2, Straube 2011). The use and applicability of 

structural rim headers in residential construction are currently limited to individually engineered 

systems for each home, whereby the builder is required to bring a professional designer into the 

building process to design—and approve—the rim header system. This results directly from the 

lack of a prescriptive method in the current building codes for the use of rim header systems. 

Therefore, the NAHB Research Center, through the Building America program, embarked on an 

effort to validate design calculations to transfer the design loads without negative effects on the 

window opening. The evaluation was performed in conjunction with a national builder, K. 

Hovnanian, to incorporate the advanced header design option for one of its models. The results 

are summarized in a previous Building America deliverable (NAHB 2009-1). However, the 

initial evaluation focused primarily on the structural capacities of the rim member in the design 

of the specific prototype home. 

1.3 Relevance to Building America’s Goals

By providing the necessary testing and research to ultimately develop a prescriptive Builders’ 

Guide to Advanced Framing for 2 × 6 frame walls, the results of this research will provide 

necessary inroads to reducing the barriers to more energy-efficient, high-R wall systems that are 

available in the residential building industry. Rather than the typical engineered system approach 

that is common when optimizing framing designs, this testing will lead to more standardized 

approaches that can be prescriptively used in building codes. It is envisioned that the guide will 

facilitate and accelerate the adoption of 2 × 6 wall framing packages by builders across all types 

of homes and climate zones. The use of 2 × 6 wall framing packages will provide opportunities 

for increasing insulation from reduced framing materials within and reduced framing factors for 

the walls, both of which lead directly to higher R-value wall systems. 

1.4 Cost Effectiveness

The current trend of advanced framing toward the use of 2 × 6 framing at 16-in. o.c. inevitably 

results in a higher material cost of construction than that of 2 × 4 framing. This research will 

provide an alternative framing system with 24-in. o.c. stud spacing, headers in rim areas only, 

reduced jack and cripple members, and offset interior wall framing that will reduce the framing 

cost of the current 2 × 6 framing techniques by reducing the lumber count and eliminating header 

material. Perhaps more importantly, this research will reduce design and labor costs associated 

with switching to, and implementing, current advanced framing methods. Reductions in design 

costs will result from the builder’s ability to apply prescriptive solutions without hiring 

additional design professionals, and labor costs will decrease because framing will decrease, both 

in the greater stud spacing and in the removal of the headers in the wall framing. 

1.5 Tradeoffs and Other Benefits

This research focuses primarily on providing builders and remodelers with a more robust 

opportunity to construct higher R-value walls and to provide a basis for a range of wall system 

performance levels when various types of insulation are considered. This effort seeks to combine 

an increase in wall cavity thermal values with a decrease in thermal shorts that degrade the 

thermal performance. Consistent with Building America goals, this research also includes 

opportunities to reduce construction costs through material and labor savings. Labor savings

result as much from the reduced structural elements that must be handled as from simplifying the 
3 

installation of products such as insulation and wiring. This research is also intended to result in a 

wall design that can be implemented with minimal additional training and has a strong 

connection to prescriptive methodologies already established in the building codes. 
4 

2 Experiment 

This individual measure laboratory testing focused on integrating rim header designs into 

standard framing methodologies. Specific results detail the laboratory testing that measured the 

performance of integrated rim header system under gravity loading with a specific focus on (1) 

the load path through the members of the assembly and (2) the window serviceability limit states. 

The results address areas where engineering design principles are ambiguous or non-applicable 

to the integrated rim header system (e.g., system-effect contributions to deflection performance) 

and are intended to be used to develop prescriptive designs and details for the integrated rim 

header system. 

2.1 Research Questions—Rim Header 

This testing is intended to provide results of rim header performance spanning a window opening 

to as much as 6 ft, and that may be applicable to a broad range of design parameters. 

Specifically, it addresses the following questions pertaining to the use of an integrated rim 

header system at the floor and spanning a 6-ft opening with 2 × 6 wall stud framing: 

• What proportion of roof gravity load is imposed on the adjacent floor framing and joist 

hangers and what is the magnitude of the additional deflection, if any, on the top sill plate 

of the opening? 

• How much deflection occurs in the top sill plate of the window opening as a result of 

floor gravity load at service load levels?

• How much can the top sill plate of the opening deflect before causing serviceability 

issues in the window? 

• What is the bearing behavior at the king stud to top plate interface with a single top plate? 

2.2 Technical Approach—Rim Header

The testing methodology is organized by component and system and was conducted in four 

stages:

• Stage 1: Component testing of the floor joist/floor truss hangers. This was designed 

to isolate and evaluate the stiffness behavior of different types of hangers that can be used 

to connect floor framing members to rim member connections. The deflection behavior 

of each hanger type was evaluated and the hanger with the lowest stiffness (worst case) 

was selected for subsequent system testing (Stages 2–4). 

• Stage 2: System testing of integrated rim header assembly with windows installed 

under roof/wall load. This evaluated the vertical load path from roof and walls 

supported by the integrated rim header, including the effect of the eccentricity in the load 

path at the second story wall-to-rim header interface. The distribution of the bearing load 

through the top plate and into the supporting king studs below was also evaluated. 

Finally, service load deflections were benchmarked and the window functionality under 

service loads was evaluated.
5 

• Stage 3: System testing of integrated rim header assembly with windows installed 

under floor load. This established the deflection behavior of the joist hangers and rough 

opening top member subjected to floor gravity loads only. Combining the results from 

Stage 2 and Stage 3 testing provides the expected behavior of an in-situ rim header 

system (see Section 3). Again, the functionality of installed windows was evaluated at 

various service load levels.

• Stage 4: System testing of integrated rim header assembly under roof/wall load to 

failure. This provided the ultimate load capacity of the tested system. 

Table 1 and Table 2 summarize the testing matrices. 

Table 1. Individual Hanger Testing Matrix

Stage Joist Hanger Hanger 

Type

No. of Nails 

per Hanger

No. of 

Tests Purpose

1 IUS 

2.06/11.88 

Facemounted 10 2 Compare stiffness 

characteristics for different 

hanger types connecting floor 

joists to the rim member. 

Results used to select hangers 

for system testing.

1 ITS 

2.37/11.88

Topmounted 4 2 

1 ITS 

3.56/11.88

Topmounted 4 2 

1 MIU 3.56/11 Facemounted 10 2 

Table 2. Rim Header System Testing Matrix

Stage Load Test 

Label

Sample 

Size

Previous 

Load to 

Specimen

Interior 

Gypsum

Max 

Test 

Loads 

Purpose

2 

Roof 

and 

wall 

load 

A 1 

Only 

preload 

level

No Service

Evaluate load path 

between integrated 

rim header and 2 × 6 

wall framing. Also, 

observe serviceability 

limits for windows in 

combination with 

integrated rim header 

system. 

B 2 

Full 

loading 

protocol 

No Service

Same as above but 

with previously tested 

specimen to evaluate 

the effects of repeated 

loading 

C 1 Full 

loading Yes Service Same as above but 

with gypsum installed 
6 

Stage Load Test 

Label

Sample 

Size

Previous 

Load to 

Specimen

Interior 

Gypsum

Max 

Test 

Loads

Purpose

protocol

3 Floor 

load 

A 2 

Only 

preload 

level

No Service

Evaluate deflection of 

sill plate under floor 

loading. Also, 

observe serviceability 

limits for windows in 

combination with 

integrated rim header 

system. 

B 2 

Full 

loading 

protocol 

No Service

Same as above but 

with previously tested 

specimen to evaluate 

the effects of repeated 

loading 

C 1 

Full 

loading 

protocol 

Yes Service Same as above but 

with gypsum installed 

4 

Roof 

and 

wall 

load 

C 1 

Full 

loading 

protocol 

Yes Failure

Determine the 

ultimate capacity of 

the integrated rim 

header system

2.2.1 Specimen Construction

Table 3 and Table 4 summarize the materials used in specimen construction; Table 5 provides 

the nailing and connections schedule. The integrated rim member and supporting wall framing 

were designed to resist the loads at the first floor level of a 20-ft wide, 2-story home with a 

center bearing wall and a ground snow load (Pg) of 50 psf. This configuration represents the 

maximum loading scenario that an integrated rim header system with a single 11⁄4-in. by 117⁄8-in. 

The TimberStrand LSL rim member can support over a span of 6 ft. A double rim member is 

required for greater roof/floor spans and/or greater. For this testing, a single rim header member 

configuration (versus a double member) was selected because the smaller associated reaction 

load-bearing area, along with the greater eccentricity of the single rim relative to the 2 × 6

framing above, create a conservative situation for evaluating the distribution of vertical roof and 

wall loads and deflection performance of the integrated rim header system. The results of this 

testing, however, will be applicable to the design of both the single and double rim member 

systems in terms of deflection and reaction load-bearing behavior. 
7 

Table 3. Individual Hanger Construction Materials 

Member Construction Materials

Rim Joist 11⁄4-in. × 117⁄8-in. TimberStrand LSL 

(1.3E product) 

Joist Hangers 

Simpson IUS 2.06/11.88 face-mounted hangers 

Simpson ITS 2.37/11.88 top-mounted hangers 

Simpson ITS 3.56/11.88 top-mounted hangers 

Simpson MIU 3.56/11 face-mounted hangers 

Floor Framing Members

TJI 210 × 117⁄8-in. I-joist

TJI 230 × 117⁄8-in. I-joist

TJI 560 × 117⁄8-in. I-joist

12 in. Deep floor truss with 2 × 4 SPF* #2 members

Joist Hangers to Rim 

Member Nailing

10d common (1.5 in. × 0.148 in.) installed per the test 

matrix and Simpson Strong-Tie Wood Construction 

Connectors Catalogue

Table 4. Rim Header System Testing Construction Materials 

Member Construction Materials

Rim Joist 11⁄4-in. × 117⁄8-in. TimberStrand LSL (1.3E product) 

Floor Joists TJI 560 × 117⁄8 I-joists, spaced 24-in. on center 

Joist Hangers Simpson ITS 3.56/11.88 top-mounted hangers 

Floor Sheathing 3⁄4-in. T&G OSB, split down the center with a T&G joint

Wall Framing

2 × 6 SPF stud grade in-line framing at 24-in. o.c. 

2 × 6 SPF #2 grade plate material, single top plate 

(2) king studs at each end of opening 

Single member at top of rough opening with infill 

framing above 

Interior Wall Sheathing 

(Stage 4 Only) 1⁄2-in. gypsum 

Windows (2) Double-hung, vinyl windows for a rough opening of 

6 ft wide × 3 ft tall, premulled together by manufacturer 
8 

Table 5. Nailing Schedule—Rim Header

Location Nailing Schedule

Floor Sheathing to 

Framing

To rim: 8d (2.5-in. × 0.131-in.) nails at 6 in. o.c. 

To floor joist: 8d (2.5-in. × 0.131-in.) nails at 12 in. o.c. 

Interior Wall Sheathing to 

Framing (Stage 4 Only)

#6 drywall screws at 12 in. o.c., first row of screws started 

8 in. from top of wall, no screw to top plate (floating joint 

at top)

Joist Hangers to Rim 

Member

(4) 10d common (1.5-in. × 0.148-in.) per Simpson StrongTie Wood Construction Connectors Catalogue

Floor Joist to Wall Top 

Plate

(2) 8d (2.5-in. × 0.113-in.) face nails through bottom 

flange (per iLEVEL Rim Board Specifier’s Guide TJ8000) 

Wall Bottom Plate to Rim 

Member Below 16d (3.5-in. × 0.135-in.) nails at 12 in. o.c. 

Rim Member to Top Plate 10d (3-in. × 0.128-in. toe nails at 6 in. o.c. 

Rough Opening Top 

Member to King Studs (2) 16d (3.5-in. × 0.135-in.) end nails 

Wall Top and Bottom 

Plates to Studs (2) 16d (3.5-in. × 0.135-in.) end nails 

Double King Studs 10d box (3-in. × 0.128-in.) face nails at 6 in. o.c., 

staggered

Figure 1 through Figure 3 provide the specimen construction for the various stages of testing. 

A typical Stage 1 test specimen consisted of 16-in. long sections of rim members, spaced 

approximately 20 in. apart. The two rim sections were connected by a single section of floor joist 

(or floor truss) supported by joist hangers attached to the rim members. 
9 

Figure 1. Stage 1 specimen construction and test set-up 

The lower portions of the Stage 2, 3, and 4 test specimens were identical (see Figure 2), and 

consisted of two side-by-side, 8-ft long × 4-ft, 3-in. high wall sections 24 in. apart. This 

configuration provided symmetrical loading and stability during testing. One of the two wall 

sections in each specimen included a 6-ft wide × 3-ft high rough opening in the center. 

For tests labeled A or B, the wall sections were unsheathed on both the interior and exterior faces

in accordance with the test matrix (see Table 2). For tests with label C, the interior face of the 

wall containing the rough opening was sheathed with a single sheet of gypsum wallboard placed 

horizontally and routed out around the interior edge of the opening. 

All walls were constructed of 2 × 6 lumber spaced at 24 in. o.c. Floor framing was TJI joists also 

spaced at 24 in. o.c. Based on the results of Stage 1 testing (see Section 3), a 31⁄2-in. wide, top-
10 

mounted joist hanger was selected to support the floor joists at either end. Specimens were 

constructed with in-line framing, per the requirements of Section R602.3.2 of the 2009 

International Residential Code for One and Two-Family Dwellings (2009 IRC) for a single top 

plate. Each test specimen also included two, 3-ft wide vinyl windows installed into the 6-ft rough 

opening. The windows were premulled together by the manufacturer. The windows were 

anchored with #10 pan head screws through every hole of the nailing flange, per the 

manufacturer’s instructions.

For the Stage 2 and Stage 4 testing, additional 2-ft high wall sections of 2 × 6 framing at 24 in. 

o.c. were added above the floor framing to provide a realistic in-situ loading mechanism to 

transfer roof load to the rim member (see Figure 3). 
11 

Figure 2. Lower portion of a typical Stage 2, 3 and 4 test specimen
12 

Figure 3. Typical Stage 2 and 4 test specimen
13 

2.3 Measurements—Rim Header

2.3.1 Test Setup and Protocol

Specimens for the integrated rim header system were tested in a Universal Testing Machine with 

an automated programmable computer control. Load was applied at an approximate rate of 0.1 

in./min of displacement. Specimens tested in Stage 1 were loaded continuously to failure. 

Specimens in Stages 2 and 3 were loaded in increments. Table 6 and Table 7 summarize the load 

levels that were applied to the specimen during Stages 2 and 3. The Stage 4 test specimen was 

loaded continuously to failure. 

Load levels for Stage 2 testing represent increments of service roof loads in a typical 20-ft wide, 

2-story house. Load levels for Stage 3 testing represent increments of service floor loads at 

typical floor span lengths in residential construction. The last load level of the Stage 2 and Stage 

3 testing protocols (Load Level 4 and Load Level 3, respectively) exceed the design load levels 

for the tested integrated rim header system, but were included to investigate the deflections at 

loads exceeding service load levels. 

At each load level, the target load was held for 5 min so the specimen could be visually inspected 

and the functionality of the installed windows could be evaluated. Window functionality was 

determined by three separate individuals manually opening and closing the windows while the 

target load was supported by the specimen. 

Table 6. Load Levels for Stage 2 Tests—Rim Header

Load Level Load to Integrated Rim 

Headera

Equivalent Roof/Wall 

Load Condition

Preload 348 plf DL only

1 497 plf 0.5 × Pg = 25 psf

2 645 plf Pg = 30 psf

3 850 plf Pg = 50 psf

4 1,063 plf Pg = 70 psf

DL ≡ dead load 

Pg ≡ ground snow load a Equivalent roof and wall load conditions assume the following: Dead load of roof framing = 

20 psf; Dead load of wall framing = 12 psf; unbalanced snow load condition for Pg as noted; 

Load Combination of D + S

Table 7. Load Levels for Stage 3 Tests—Rim Header

Load Level Load to Integrated Rim 

Headera Floor Span

Preload 50 plf DL only

1 200 plf 10 ft

2 360 plf 18 ft

3 480 plf 24 ft

a Equivalent floor load conditions assume the following: Dead load of floor framing = 10 psf; 

Live load of floor = 30 psf; Load Combination of D + L
14 

2.4 Equipment—Rim Header

A summary of the integrated rim header test locations for deformations measured in each stage 

of testing follows: 

• Stage 1

o Movement of the bottom of joist relative to the rim member 

• Stages 2 and 3

o Movement of the bottom of joist relative to the rim member at each hanger 

o Movement of the wall top plate relative to the rim member at each hanger 

o Movement of the wall top plate relative to the top of the king studs at the bearing 

surface interface (both interior and exterior edges of the plate) 

o Midspan deflection of the rough opening top member (at both the interior and 

exterior faces) relative to the support studs 

• Stage 4

o Midspan deflection of the rough opening top member (at both the interior and 

exterior faces) relative to the support studs

A data acquisition system integrated with the proprietary control software (Partner software by 

Instron) was used to record instrument readings, including load and deflection measurements. 

Refer to Figure 1 for loading and instrumentation of Stage 1 test specimens. Figure 4 and Figure 

5 provide schematics of the Stage 2 and Stage 3 loading conditions and instrumentation 

locations. The Stage 4 test specimen was tested using the same loading configuration as those 

tested in Stage 2. Figure 6 and Figure 7 provide photos of the Stage 1 and Stage 2 testing setups, 

respectively. 
15 

Figure 4. Typical Stage 2 and 4 test set-up 
16 

Figure 5. Typical Stage 3 test set-up
17 

Figure 6. Stage 1 test setup
18 

Figure 7. Stage 2 test setup
19 

3 Analysis 

3.1 Analysis of Results

3.1.1 Stage 1 Results

Figure 8 shows the load-deformation behavior of the various individual joist or floor truss 

hangers tested. Deflection was calculated as the average movement of the floor joist (or truss)

relative to the rim header at the four measured locations (see Figure 1). Results of the Stage 1 

testing show that the wider, top-mounted joist hanger (ITS3.56-11.88) exhibited the highest 

deformation within the range of design floor loads evaluated during Stage 3 testing (400 

lb/hanger–960 lb/hanger). Therefore, the ITS3.56-11.88 joist hanger was used in the Stage 2, 

Stage 3 and Stage 4 system testing to evaluate the worst-case scenario in terms of deflection 

performance.

Figure 8. Stage 1 test results

3.1.2 Stage 2 Results

Figure 9 and Figure 10 provide the load versus deflection plots for the movement of the rough 

opening top member relative to the king studs during Stage 2 testing (roof loading), measured at 

the exterior and interior faces of the sill, respectively. Figure 11 provides the load versus 

deflection plots for the average movement of the joist hangers relative to the rim during Stage 2 

testing. Figure 12 and Figure 13 provide the load versus deflection plots for the average 

movement at the bearing locations between the supporting king studs and the wall top plates 

exterior and interior faces, respectively. In all cases, load is presented in pounds per linear foot 

(plf) along the opening. 

0

200

400

600

800

1,000

1,200

0 0.05 0.1 0.15 0.2 0.25

Load (lb / hanger)

Deflection (in)

Individual Joist Hanger Tests

ITS3.56-11.88 - 1

ITS3.56-11.88 - 2

ITS2.37-11.88 - 1

ITS2.37-11.88 - 2

IUS2.06-11.88 - 1

IUS2.06-11.88 - 2

MIU3.56-11 - 1

MIU3.56-11 - 2
20 

Figure 9. Stage 2 rough opening top member midspan deflections (exterior face)

Figure 10. Stage 2 rough opening top member midspan deflections (interior face)

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Window Sill Mid-Span Deflection Exterior Face (Stage 2)

Stage 2-1b

Stage 2-2a

Stage 2-2b

Stage 2-2c

Predicted

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Window Sill Mid-Span Deflection Interior Face (Stage 2)

Stage 2-1b

Stage 2-2a

Stage 2-2b

Stage 2-2c

Predicted
21 

The integrated rim header system successfully limited deflections and maintained window 

serviceability throughout all tested load levels. Plots of the midspan deflection of the window top 

sill show that the interior face deflected approximately 2.5 times more than the exterior face. 

This difference is most likely attributable to the support provided by the window flange attached 

to the exterior face of the window top sill. A plot of predicted midspan deflection caused by roof 

load is included in Figure 9 and Figure 10 for comparison with the measured values. This 

predicted deflection plot is calculated using the load applied to the rim member and the rim 

header deflection equation per the manufacturer’s literature, with the addition of the predicted 

movement of the joist hangers relative to the rim header member. Refer to Appendix A for 

further explanation and derivation of deflection design equations. Figure 9 and Figure 10 show 

that all the Stage 2 tests exhibited less deflection than predicted, indicating that the design 

methodology for calculating deflections caused by roof loading proposed herein is conservative. 

Figure 11. Stage 2 average movement of joist hangers relative to rim header

The integrated rim header system also successfully provided a complete vertical load path 

through the rim header member. Some movement of the joist hangers within the system during 

Stage 2 testing (roof loading) was observed (see Figure 11), indicating the load transferred 

slightly between the load-bearing walls above and the floor framing. Comparing the movement 

of the joist hanger in the Stage 2 testing and deformation measured at the same load from the 

individual hanger tests (Stage 1) yields an approximate load of 160 lb being transferred to each 

hanger at the maximum roof design load, or 8% of the total roof load on a per-hanger basis. This 

load can be accounted for in the sizing of the joist hangers and should have no adverse effect on 

the overall design of the system. 

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Movement of Joist Relative to Rim (Stage 2)

Stage 2-1b

Stage 2-2a

Stage 2-2b
22 

Figure 12. Stage 2 bearing deformations of top plate (exterior edge)

Figure 13. Stage 2 bearing deformations of top plate (interior edge)

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Bearing Deformation of Top plate at Exterior Face (Stage 2)

Stage 2-1b

Stage 2-2a

Stage 2-2b

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Bearing Deformation of Top plate at Interior Face (Stage 2)

Stage 2-1b

Stage 2-2a

Stage 2-2b
23 

Test measurements of the wall top plate deformations at the king stud bearing locations show a 

difference in the crushing deformations between the interior and exterior edges of the top plate; 

the crushing at the exterior edge of the top plate is approximately 2.4 times greater than at the 

interior edge. This is the result of the eccentricity between the center of the rim joist and the 

center of the stud. The eccentricity leads to a non-uniform loading distribution at the stud-toplate interface. Based on the magnitudes of the measured deformations, and assuming that 

deformation is proportional to stress, the bearing stress distribution at the stud-to-plate interface 

is trapezoidal (Figure 14a); the interior edge of the plate is at approximately half the stress of the 

exterior edge. For design purposes, this stress distribution can be conservatively reduced to a 

triangular distribution across the king stud (Figure 14b). 

Figure 14. Bearing deformations and simplified stress distribution at 

king stud-to-top plate interface

The tested configuration also performed acceptably in terms of the magnitude of the observed 

bearing deformation; the average deformation was <0.04 in. at the greatest test design load (see 

Table 6). The 0.04-in. threshold is the basis for establishing the referenced design values for 

wood compression perpendicular to the grain (NDS). The NDS also notes that this deformation 

limit “...has been shown by experience to provide adequate service in typical wood frame 

construction” (AF&PF 2005). Therefore, bearing deformations and more specifically any minor 

contribution that they may have to the overall midspan deflections of the system need not be 

included in design. 

3.1.3 Stage 3 Results

Figure 15 and Figure 16 provide the load versus deflection plots for the window top sill relative 

to the king studs under floor loading (Stage 3) measured at the exterior and interior faces of the 

sill, respectively. Figure 17 provides the load versus deflection plots for the average movement 

of the joist hangers relative to the rim during Stage 3 testing. Figure 18 and Figure 19 provide the 

load versus deflection plots for the average movement at the bearing locations between the 
24 

supporting king studs and the wall top plates exterior and interior faces, respectively. In all cases,

load is presented in pounds plf along the opening. 

Figure 15. Stage 3 rough opening top member midspan deflections (exterior face)

Figure 16. Stage 3 rough opening top member midspan deflections (interior face)

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Window Sill Mid-Span Deflection Exterior Face (Stage 3)

Stage 3-1a

Stage 3-1b

Stage 3-2a

Stage 3-2b 

Stage 3-2c

Predicted

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Window Sill Mid-Span Deflection Interior Face (Stage 3)

Stage 3-1a

Stage 3-1b

Stage 3-2a

Stage 3-2b 

Stage 3-2c

Predicted
25 

Midspan deflection results for the rough opening top member in Stage 3 testing show an even 

greater disparity between the interior and exterior faces; the interior face exhibits on average 4 

times more deflection. This increase is attributable to the load transfer through the floor joists, 

which leads to greater joist hanger deformations (see Figure 17). The midspan deflection at 

either face is again lower than that predicted by design calculations. Figure 15 and Figure 16

include the predicted deflection behavior plot for comparison. Predicted deflections are 

calculated using the same methodology that was used in the Stage 2 results analysis, except that 

the full floor loading (which is being transferred to the rim header member through the joist 

hangers) is now used in conjunction with the individual hanger test results to determine 

additional hanger movement relative to the rim. The better-than-predicted performance of the 

integrated rim header system again indicates that the proposed deflection calculation 

methodology is conservative and appropriate for use in further design methodologies. 

Figure 17. Stage 3 average movement of joist hangers relative to rim header

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Movement of Joist Relative to Rim (Stage 3 Loading)

Stage 3-1

Stage 3-1b

Stage 3-2

Stage 3-2b
26 

Figure 18. Stage 3 bearing deformations of top plate (exterior edge)

Figure 19. Stage 3 bearing deformations of top plate (interior edge)

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Bearing Deformation of Top plate at Exterior Face (Stage 3)

Stage 3-1a

Stage 3-1b

Stage 3-2a

Stage 3-2b

0

200

400

600

800

1,000

1,200

-0.01 0.04 0.09 0.14 0.19 0.24

Load (lb / ft)

Deflection (in)

Bearing Deformation of Top plate at Interior Face (Stage 3)

Stage 3-1a

Stage 3-1b

Stage 3-2a

Stage 3-2b
27 

The crushing deformations of the wall top plate also correspondingly changed (see Figure 18 and 

Figure 19). The movement of the interior and exterior faces of the plate was nearly equal, 

indicating that the full bearing surface (i.e., the full 11⁄2-in. × 51⁄2-in.) of the king stud was 

engaged and equally loaded. This result further confirms that the use of a simplified triangular

stress distribution in the bearing capacity design of the king stud-to-top plate interface is 

conservative. 

3.1.4 Stage 4 Results 

Stage 4 testing concluded with the integrated rim header specimen tested to failure under the roof 

load case. The specimen failed at 4,540 plf of load applied to the integrated rim header, with no 

damage to the integrated rim header system or window. The primary failure mode was the walls 

supported by the rim header assembly (capacity of the integrated rim header was not reached)

lost stability. After the load was released, the installed windows showed little to no decrease in 

operability, even though the rough opening top member was subjected to a >3⁄4-in. midspan 

deflection, further indicating the integrated rim header system exceeds the minimal acceptable 

performance.

3.2 Example Design Calculation

Provided is an example design calculation of midspan rough opening top member deflections of 

the integrated rim header system configuration tested during this research project. Deflections 

caused by the roof and floor loadings are calculated separately in accordance with the design 

methodologies previously outlined that account for the additional deflections caused by joist 

hanger movement relative to the rim. Deflections from each loading are additive and are summed 

to calculate total deflections within the system. 

The deflections were calculated for live load only and live plus dead load, and total load 

deflections when supporting the loads at the first floor level of a typical 20-ft wide, 2-story home 

with a center bearing wall and a ground snow load of 50 psf. Refer to Appendix A for the 

specific design equations and calculations.

The predicted midspan deflection of the system at the rough opening top member when resisting 

live load only was 0.1275 in. The predicted deflection of the system when resisting the total 

design load was 0.2211 in. These correspond to L/565 and L/326 deflections, respectively, given 

the 6-ft opening, and both exceed the code specified deflection limits of L/360 and L/240 for 

header members. 
28 

4 Conclusions

Based on the results of this testing, the following conclusions can be drawn about the 

performance of the integrated rim header system:

1. The integrated rim header system successfully maintains window serviceability 

throughout typical residential service load levels. No decrease in window operability was 

observed at any tested load levels, under either roof or floor loading. 

2. The rim header system also successfully provides a continuous vertical load path for roof 

loading through the bearing walls above and into the rim member. Approximately 8% of 

the imposed roof load is imposed on the adjacent floor framing and joist hangers. This 

load can be accounted for in the sizing of the joist hangers. 

3. The joist hangers moved relative to the rim header member under both load scenarios 

(albeit significantly less under roof loads) and contributed to deflection of the top sill 

plate of the opening. 

4. Appropriate design calculations for the rough opening top member within the rim header 

system encompass the published deflection equations for the rim member as well as 

additional deflections caused by the movement of the joist hangers. Comparison between 

test results and predicted deflection behavior using this methodology shows that the 

integrated rim header system consistently exhibits better than expected deflection 

performance, indicating the presence of a system effect factor. Results indicate that it is 

appropriate to use published rim header deflection equations in conjunction with the 

hanger deflection contribution methods described in this report to design an integrated 

rim header system. 

5. Wood-bearing capacity design assumes uniform stress distribution calculating bearing 

area of the king stud to top plate interface. Crushing deformations measured during 

testing indicated that although the entire face of the king stud was engaged in bearing, the 

stress distribution was not uniform and varied by approximately 50% from inside face to 

outside face of the top plate. For simplicity, a triangular stress distribution is suggested 

when evaluating the bearing capacity of the king stud to top plate interface. Crushing 

deformations were also less than the 0.04-in. threshold used to establish referenced wood 

bearing design values. 

6. Testing of the system to failure yielded an ultimate test load of 4,540 plf and a primary 

failure mode of loss of stability of the walls supported by the rim header assembly. 

Therefore, the ultimate capacity of the integrated rim header system is greater than the 

observed ultimate test load. Also, the installed windows showed little to no decrease in 

operability after the test load was released, even though the rough opening top member 

underwent a >3⁄4-in. midspan deflection. 
29 

References 

AF&PF 2005, National Design Specification for Wood Construction (NDS)—2005 Edition, 

ANSI / AF&PS NDS-2005, January 2005. 

IRC 2009, 2009 International Residential Code for One- and Two-family Dwellings, 

International Code Council, Inc., 2009. 

NAHB Research Center (2009-1), “Gate 1B - System Evaluations & Specifications: Advanced 

Header Framing Design for High-R Wall Systems”, Deliverable Number 4.2.1.2, NREL 

Subcontract Number AXL-9-99208-01, December 2009. 

NAHB Research Center (2009-2), “Summary of Code and Standard Barriers to the 

Implementation of High Performance Home Systems Designs”, Deliverable Number 4.2.2.1, 

NREL Subcontract Number AXL-9-99208-01, December 2009. 

Straube, J. (2011). “High R-value Enclosures for High Performance Residential Buildings in All 

Climate Zones.” Research Report 1005. Building Science Corporation, Sommerville, MA. 
30 

Appendix A 

Example Design Calculation

20-foot wide house, Pg = 50-psf, 2-story house, center bearing wall 

Span Length: 6 ft 

Rim Member Properties:

 b: 1.25 in. 

 d: 11.875 in. 

 E: 1,300,000 psi 

Loads to the Integrated Rim Header System

Applicable Load Combo: D+0.75L+0.75S 

Roof Dead Load + Wall Dead Load (Droof): 348 plf 

Floor Dead Load (Dfloor): 50 plf 

Roof Snow Load (S): 502 plf 

Floor Live Load (L): 150 plf 

Midspan Deflection Equations:

Δ = Δrim + Δhanger-rim (Eq. 1) 

Δrim = per iLevel ESR Report (ESR 1387) 

= [(270 wL4) / (Ebd3)] [(28.8wL2) / (Ebd)] (Eq. 2) 

Where:

 w: Load to member (plf) 

 L: Span length (ft)

 E: Material modulus of elasticity (psi)

 b: Member width (in)
31 

 d: Member depth (in) 

Δhanger-rim = P × M (Eq. 3) 

Where:

Proof = w × A × 8% (Eq. 4a) 

Where:

 w: Load to member (plf) 

 A: Trib. area to single hanger 

8%: is the amount of roof load transferred to a single hanger, derived from results of Stage 2 

testing in this report 

OR

Pfloor = w × A (Eq. 4b) 

Where:

 w: Load to member (plf) 

 A: Trib. area to single hanger

M: 0.000135 in./lb (The slope of the load versus deflection behavior from the individual hanger 

testing) 

Live Load Deflection at Top Sill Plate

Roof Loading Condition 

Δroof = Δrim + Δhanger-rim

= [(270)(0.75 × 502 plf)(6’)4 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)3] 

+ [(28.8)(0.75 × 502 plf)(6’)2 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)] 

+ [(0.75 × 502 plf)(2’)(0.08)(0.000135-in./lb)

= 0.0768 in. 
32 

Floor Loading Condition 

Δfloor = Δrim + Δhanger-rim

= [(270)(0.75 × 150 plf)(6’)4 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)3] 

+ [(28.8)(0.75 × 150 plf)(6’)2 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)] 

+ [(0.75 × 150 plf)(2’)(0.000135-in./lb)

= 0.0508 in. 

System Deflection

Δsystem = Δroof + Δfloor

 = 0.0768 in. + 0.0508 in. 

 = 0.1276 in. or L/565 

Total Load Deflection at Top Sill Plate

Roof Loading Condition 

Δroof = Δrim + Δhanger-rim

= [(270)(348 plf + 0.75 × 502 plf)(6’)4 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)

3

] 

+ [(28.8)(348 plf + 0.75 × 502 plf)(6’)2

 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)] 

+ [(348 plf + 0.75 × 502 plf)(2’)(0.08)(0.000135-in./lb)

= 0.1477” 

Floor Loading Condition 

Δfloor = Δrim + Δhanger-rim

= [(270)(50 plf + 0.75 × 150 plf)(6’)4 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)3] 

+ [(28.8)(50 plf + 0.75 × 150 plf)(6’)2

 / (1.3 × 106 psi)(1.25-in.)(11.875-in.)] 

+ [(50 plf + 0.75 × 150 plf)(2’)(0.000135-in./lb)

= 0.0734 in. 
33 

System Deflection

Δsystem = Δroof + Δfloor

 = 0.1477 in. + 0.0734 in. 

 = 0.2211 in. or L/326 
DOE/GO-102013-3595 ▪ January 2013

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