NISTIR 6938 

EXPERIMENTAL TESTING OF ROOF TO WALL 

CONNECTIONS IN WOOD FRAME HOUSES 

Michael A. Riley and Fahim Sadek 

Building and Fire Research Laboratory

Gaithersburg, MD 20899-8611

United States Department of Commerce 

Technology Administration 

National Institute of Standards and Technology

NISTIR 6938 

EXPERIMENTAL TESTING OF ROOF TO WALL 

CONNECTIONS IN WOOD FRAME HOUSES 

Michael A. Riley and Fahim Sadek 

April 2003 

Building and Fire Research Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899-8611

United States Department of Commerce 

Donald L. Evans, Secretary

Technology Administration 

Phillip J. Bond, Under Secretary for Technology

National Institute of Standards and Technology

Arden L. Bement, Jr., Director

Experimental Testing of Roof to Wall Connections in Wood Frame Houses

ABSTRACT

The majority of residential construction in the United States is wood-frame construction.

These buildings perform well under gravity loads, but considerable damage has been observed in such structures after significant earthquakes and major hurricanes. This is due to

weaknesses inherent in current wood-frame construction and underscores the need for improving the structural performance of typical homes. To enhance the resistance of houses to

natural disasters and to reduce the risk to life and property, the behavior of wood-frame buildings subjected to dynamic and lateral loads needs to be better understood. These buildings

are typically constructed from diaphragms that are joined by inter-component connections,

which can greatly influence the overall behavior of the structure. An understanding of the behavior of each of the structural components and connections is essential to accurately predict

the performance of a housing unit under different types of loading. 

While the response of many of the components of wood-frame houses are well documented,

there is a lack of performance data for inter-component connections between intersecting

walls, roofs and walls, and walls and foundations. Since post-event investigations of several

recent disasters indicate that failure of inter-component connections played a large role in the

failure of many structures, the response of such connections needs to be better understood. To

achieve this, experiments are needed to investigate how these connections respond as they are

loaded to failure. The resulting experimental data can be used to develop improved analytical

models of wood-frame structures, which can be used to design houses that are better able to

resist extreme loads. 

This report describes the results of a series of tests on two types of roof to wall connections.

These test results show how the connections are likely to perform when subjected to strong

winds or seismic loads. The results of the tests provide data necessary for the development of

improved analytical models of the connection response, which could in turn lead to improved 

design tools for wood-frame construction, and to stronger and more structurally efficient residential buildings. 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

ACKNOWLEDGEMENTS

This effort was supported by the Materials and Construction Research Division, Building and 

Fire Research Laboratory, National Institute of Standards and Technology, U.S. Department of

Commerce. The authors wish to thank Frank Davis, Andre Witcher, Mark Kile, and Max Peltz

who provided valuable assistance in the laboratory testing. Jason McCormick’s assistance in

analyzing the experimental data is greatly appreciated. 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

CONTENTS

Abstract ......................................................................................................................... iii

Acknowledgements ...................................................................................................... v

Contents ........................................................................................................................vii

List of Figures ...............................................................................................................ix

List of Tables................................................................................................................. xi

1 Introduction............................................................................................................. 1

1.1 Background.............................................................................................................................. 2

1.1.1 Experimental Studies......................................................................................................... 3

1.1.2 Analytical Studies.............................................................................................................. 3

1.2 Research Objectives............................................................................................................... 3

1.3 Scope of Current Effort ......................................................................................................... 4

2 Overview of Test Program.................................................................................... 5

2.1 Test Specimens ....................................................................................................................... 5

2.1.1 Roof to Wall Connections Tested ....................................................................................... 7

2.2 Test Setup ................................................................................................................................ 8

2.3 Instrumentation and Data Acquisition............................................................................ 10

2.4 Test Protocols ........................................................................................................................ 14

3 Results of Uplift Load Tests............................................................................... 17

3.1 Response with Toe-nailed Connections .......................................................................... 17

3.2 Response with Hurricane Clips......................................................................................... 18

3.3 Comparison of Responses .................................................................................................. 18

4 Results of Monotonic Lateral Load Tests ........................................................ 27

4.1 Response with Toe-nailed Connections .......................................................................... 27

4.2 Response with Hurricane Clips......................................................................................... 27

4.3 Comparison of Responses .................................................................................................. 33

5 Results of Cyclic Lateral Load Tests................................................................. 39

5.1 Response with Toe-nailed Connections .......................................................................... 39

5.2 Response with Hurricane Clips......................................................................................... 39

5.3 Comparison of Responses .................................................................................................. 47

6 Results of Combined Uplift and Lateral Load Tests..................................... 49

6.1 Response with Toe-nailed Connections .......................................................................... 49

6.2 Response with Hurricane Clips......................................................................................... 49

6.3 Comparison of Responses .................................................................................................. 55

7 Conclusions ........................................................................................................... 61

8 References.............................................................................................................. 65

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LIST OF FIGURES

Figure 2.1. Sketch of a typical test specimen. ..................................................................................... 5

Figure 2.2. Typical test specimen before instrumentation................................................................ 6

Figure 2.3. Side view of specimen........................................................................................................ 7

Figure 2.4. Front view of specimen...................................................................................................... 7

Figure 2.5. Hurricane clip of the type used. ....................................................................................... 8

Figure 2.6. Dimensions of hurricane clips. ......................................................................................... 8

Figure 2.7. Sketch of specimen for lateral load test ......................................................................... 10

Figure 2.8. Sketch of specimen for uplift load test............................................................................. 9

Figure 2.9. Sketch of specimen for combined vertical and lateral load test................................. 11

Figure 2.10. Locations of displacement sensors and load cells on the specimens. ..................... 13

Figure 2.11. Generic lateral displacement curve for cyclic lateral load tests. .............................. 16

Figure 3.1. Failure of toe-nailed truss to wall connection............................................................... 17

Figure 3.2. Vertical displacement applied to specimen with toe-nailed connections.................. 19

Figure 3.3. Vertical load applied to specimen with toe-nailed connections. ................................ 19

Figure 3.4. Connection deformation response of specimen with toe-nailed connections. ......... 20

Figure 3.5. Load-deformation response of specimen with toe-nailed connections. ................... 20

Figure 3.6. Failure of hurricane clip connection............................................................................... 21

Figure 3.7. Vertical displacement applied to specimen with hurricane clips............................... 22

Figure 3.8. Vertical load applied to specimen with hurricane clips............................................... 22

Figure 3.9. Connection deformation response of first test with hurricane clips. ......................... 23

Figure 3.10. Load-deformation response of first test with hurricane clips. .................................. 23

Figure 3.11. Connection deformation response of second test with hurricane clips. .................. 24

Figure 3.12. Load-deformation response of second test with hurricane clips.............................. 24

Figure 3.13. Comparison of responses with toe-nailed connections and hurricane clips.......... 25

Figure 4.1. Failure of toe-nailed connection with lateral load. ....................................................... 28

Figure 4.2. Lateral displacement applied to specimen with toe-nailed connections................... 29

Figure 4.3. Lateral load applied to specimen with toe-nailed connections................................... 29

Figure 4.4. Lateral displacement responses for trusses with toe-nailed connections.................. 30

Figure 4.5. Uplift displacement responses for trusses with toe-nailed connections.................... 30

Figure 4.6. Lateral force-displacement responses for trusses with toe-nailed connections........ 31

Figure 4.7. Uplift force-displacement responses for trusses with toe-nailed connections.......... 31

Figure 4.8. Comparison of lateral and vertical responses for inner truss with toe-nailed 

connections................................................................................................................... 32

Figure 4.9. Comparison of lateral and vertical responses for outer truss with toe-nailed 

connections................................................................................................................... 32

Figure 4.10. Failure of hurricane clip connection with lateral load................................................ 33

Figure 4.11. Lateral displacement applied to specimen with hurricane clips .............................. 34

Figure 4.12. Lateral load applied to specimen with hurricane clips .............................................. 34

Figure 4.13. Lateral displacement responses for trusses with hurricane clips. ............................ 35

Figure 4.14. Uplift displacement responses for trusses with hurricane clips. .............................. 35

Figure 4.15. Lateral force-displacement responses for trusses with hurricane clips. .................. 36

Figure 4.16. Uplift force-displacement responses for trusses with hurricane clips. .................... 36

Figure 4.17. Lateral and vertical responses for inner truss with hurricane clips. ........................ 37

Figure 4.18. Lateral and vertical responses for outer truss with hurricane clips. ........................ 37

Figure 4.19. Comparison of responses of inner trusses. .................................................................. 38

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

Figure 4.20. Comparison of responses of outer trusses. .................................................................. 38

Figure 5.1. Failure of toe-nailed connection with cyclic load.......................................................... 40

Figure 5.2. Lateral displacement applied to specimen with toe-nailed connections................... 41

Figure 5.3. Lateral load applied to specimen with toe-nailed connections................................... 41

Figure 5.4. Lateral displacement responses for trusses with toe-nailed connections.................. 42

Figure 5.5. Uplift displacement responses for trusses with toe-nailed connections.................... 42

Figure 5.6. Lateral force-displacement responses for trusses with toe-nailed connections........ 43

Figure 5.7. Uplift force-displacement responses for trusses with toe-nailed connections.......... 43

Figure 5.8. Lateral displacement applied to specimen with hurricane clips. ............................... 44

Figure 5.9. Lateral load applied to specimen with hurricane clips. ............................................... 44

Figure 5.10. Lateral displacement responses for trusses with hurricane clips. ............................ 45

Figure 5.11. Uplift displacement responses for trusses with hurricane clips. .............................. 45

Figure 5.12. Lateral force-displacement responses for trusses with hurricane clips. .................. 46

Figure 5.13. Uplift force-displacement responses for trusses with hurricane clips. .................... 46

Figure 6.1. Failure of toe-nailed connection with combined load.................................................. 50

Figure 6.2. Displacements applied to specimen with toe-nailed connections. ............................. 51

Figure 6.3. Loads applied to specimen with toe-nailed connections. ............................................ 51

Figure 6.4. Lateral displacement responses for trusses with toe-nailed connections.................. 52

Figure 6.5. Uplift displacement responses for trusses with toe-nailed connections.................... 52

Figure 6.6. Lateral force-displacement responses for trusses with toe-nailed connections........ 53

Figure 6.7. Uplift force-displacement responses for trusses with toe-nailed connections.......... 53

Figure 6.8. Lateral and vertical responses for inner truss with toe-nailed connections.............. 54

Figure 6.9. Lateral and vertical responses for outer truss with toe-nailed connections.............. 54

Figure 6.10. Failure of hurricane clip connection with combined load. ........................................ 55

Figure 6.11. Displacements applied to specimen with hurricane clips. ........................................ 56

Figure 6.12. Loads applied to specimen with hurricane clips......................................................... 56

Figure 6.13. Lateral displacement responses for trusses with hurricane clips. ............................ 57

Figure 6.14. Uplift displacement responses for trusses with hurricane clips. .............................. 57

Figure 6.15. Lateral force-displacement responses for trusses with hurricane clips. .................. 58

Figure 6.16. Uplift force-displacement responses for trusses with hurricane clips. .................... 58

Figure 6.17. Lateral and vertical responses for inner truss with hurricane clips. ........................ 59

Figure 6.18. Lateral and vertical responses for outer truss with hurricane clips. ........................ 59

Figure 6.19. Comparison of responses of inner trusses.................................................................... 60

Figure 6.20. Comparison of responses of outer trusses. .................................................................. 60

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

LIST OF TABLES

Table 2.1. Displacement sensors used to measure the specimen motion..................................... 12

Table 2.2. Load cells used to measure the uplift loads applied to the roof sheathing................ 14

Table 2.3. Additional sensors measured during the tests............................................................... 14

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

1 INTRODUCTION

The majority of residential construction in

the United States is wood-frame buildings.

These buildings perform well under gravity

loads, but considerable damage has been

observed after significant earthquakes and

major hurricanes. Recent natural disasters

have caused major damage to them, which

has resulted in large economic losses. As

examples, the tornado that struck Oklahoma City on 3 May 1999 demolished more

than 2200 homes and damaged over 7000

more, while losses to residential construction represented about 72 % of the $15.3 billion in total insured losses from the 1994

Northridge earthquake. 

Such disasters highlight the weaknesses inherent in current wood-frame construction

and underscore the need for improving the

structural performance of typical homes.

To enhance the resistance of houses to natural disasters and to reduce the risk to life

and property, the behavior of wood-frame

buildings subjected to dynamic and lateral

loads needs to be better understood. 

Wood-frame buildings are constructed from

several diaphragms such as walls, floors,

and roofs; joined by inter-component connections such as nails, anchor bolts, metal

plates, and other proprietary connectors.

The structural performance of these buildings is influenced by the behavior of their

individual components and connections.

Therefore, an understanding of the behavior

of the different structural components and

connections is essential to accurately predict

the performance of a housing unit under

different types of loading. 

Analysis of the structural response of woodframe building components subjected to

lateral loads is a difficult task due to several

sources of nonlinearity, the complex nature

of the connections, and a wide variability in

material properties and construction techniques. Since shear walls are the most important elements for resisting lateral loads,

they have been experimentally and analytically studied since the early 1970s. Simplified methods of wall analysis and finite

element models have been developed to

predict the behavior of the walls under

static and dynamic lateral loading. 

The development of tools for analyzing

complete wood-frame houses started in the

mid-eighties, but few investigators have

attempted to analyze the different structural

components and the inter-component connections in an assembled model. This is

due, in part, to the lack of performance data

for inter-component connections between

intersecting walls, roof and walls, and walls

and foundations. Since post-event investigations of several recent disasters indicated

that in many cases failure of the intercomponent connections played a large role 

in the failure of the structure, such connections need to be incorporated into the performance models. To achieve this, experiments are needed to investigate how these

connections behave, as they are loaded to

failure. 

The NIST research plan is to develop experimentally validated, three-dimensional,

analytical models to predict the performance of housing units during natural disasters. Such models can be used to establish

performance characteristics of conventional

and innovative housing systems. The current effort consisted of testing the intercomponent connections between roof 

trusses and walls, in a full-scale roof and

wall assembly. The intent is to determine

the performance of the connections when

they are part of a complete system. The results of these tests can be combined with the

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

o Inadequate bracing (cripple walls, total

absence of shear walls, large wall openings, inadequate let-in bracing). 

results of sub-component tests to develop

more accurate analytical models. 

1.1 Background 

o Component separation (masonry fireplaces and chimneys, masonry veneers,

porch roofs and other overhangs, different house sections). 

Although recent earthquakes and hurricanes in the United States have resulted in

few casualties, they have caused substantial

damage, significant economic loss, and disruption of social and commercial activities.

The performance of residential housing during such events has shown that wood-frame

construction generally meets the life safety

objective. Many houses, however, have experienced structural and nonstructural 

damage that prevented immediate occupancy, and resulted in expensive repairs. 

o Non-uniform or irregular distribution of 

stiffness, due to irregular plans and elevations (split level house, setbacks),

which leads to torsional movements. 

o Poor detailing or quality of construction. 

o Lack of continuous load path from roof

to foundation. 

Post-earthquake investigations have indicated that much of the seismic damage can 

be attributed to construction flaws or inadequate quality assurance, including missing fasteners, overdriving of nails, improper

placement of anchor bolts, and misplaced

nails. The preference for more open interior 

spaces, hillside homes, soft stories due to

garage openings, and more irregularly 

shaped structures may also be contributing

factors. Poor soil conditions (liquefaction,

excessive settlement) and location (building

on a hill-side) have been also cited as causes

of damage. Houses built in accordance with

seismic codes were generally found to perform well. 

In past hurricanes, the main cause of severe

damage to wood-frame houses has been 

roof damage, due to inadequate anchorage

of the roof framing to the wall, damage to 

the shingles and other roof coverings, and

loss of roof sheathing. Foundation failure

and inadequate anchorage of the structure

to the foundation have also caused failures.

Similar to earthquake performance, issues

such as continuous load path and structural

integrity are crucial for hurricane resistance,

particularly because water damage from

roof failures is a major contributor toward

the economic losses. In addition to water

damage, the internal pressure in a house is

increased due to breaches in the building

envelope from missiles, thereby contributing to roof failures. Properly installed plywood boards over windows or storm shutters, doors, and garage doors can alleviate

this problem, but improperly installed

boards and shutters can contribute to the

damage from wind-borne debris. 

In general, poor seismic performance of 

wood-frame houses has been observed

when the house did not respond as a unit,

due to discontinuous load paths. Common 

practices that lead to a lack of integrity include: 

o Insufficient or poorly detailed intercomponent connections (anchorage to

foundation, wall-to-wall connections,

wall-to-roof or floor connections). 

NIST has published a comprehensive stateof-the-art report on the structural performance of single-family, wood-frame housing

(Yancey et al., 1998), which includes a detailed literature review of experimental and

2 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

analytical studies conducted on complete

houses, in addition to wood subassemblies,

such as shear wall diaphragms, and various

connections. While some of the salient findings are summarized below, greater detail

may be found in the NIST report. 

1.1.1 Experimental Studies 

Shear wall behavior under lateral loads has

been the focus of a significant number of

studies. Tests have been conducted under

monotonic, cyclic, and dynamic loads to

investigate the response characteristics of

the walls. Several additional studies have

tested the sheathing-to-framing connections

to determine their response characteristics,

determine their resistance, and provide data

for analytical modeling, since they have

been shown to be a critical element in the

wall performance. 

A relatively small number of full-scale

houses have been tested. Tests have been

performed on single- and two-story houses

under field and laboratory conditions. 

Very few experimental studies have been

conducted on inter-component connections.

See, for example, Rosowsky et al. (1998) and

Reed et al. (1996, 1997). Testing of these

connections is important, since they are key

elements for the wood-frame buildings, and

they must perform well for the structure to 

respond in an integrated fashion. An invitational workshop on seismic testing, analysis, and design of wood-frame construction

(Seible et al., 1999) recognized that the behavior of inter-component connections is

not well understood and recommended further testing of such connections. 

1.1.2 Analytical Studies 

Analyzing the structural components of a

wood-frame building subjected to lateral

loads is essential to understand their performance during natural disasters. Since

shear walls are the most important elements

in resisting lateral loads, several investigators have extensively studied them since the

early 1970s. Simplified analysis methods

and finite element models were developed

to predict the nonlinear behavior of the

walls under static lateral loading. A few

researchers also attempted to predict the

dynamic behavior of the walls subjected to

earthquake ground motion. 

The development of analytical tools for analyzing complete wood-frame houses started

in the mid 1980s. This work included analyzing the different structural components,

as well as the inter-component connections

in an assembled model. Comparisons with 

experimental studies were performed to

assess the validity of the proposed models 

and analyses. To date, only limited research

has been directed toward the analysis of a

complete building or to the response of the

inter-component connections (Polensek and

Schimel, 1986, 1988; Groom and Leichti,

1991, 1994). 

1.2 Research Objectives 

The long term objective of the NIST research is to develop the metrics and predictive tools necessary for evaluating the structural performance of housing systems during natural disasters, including earthquakes

and strong winds. The program is expected 

to lead to buildings that can better resist extreme loads and a reduction in construction

costs for the housing industry. 

To reach this objective, experimentally validated, three-dimensional finite element

models of typical systems and structural

performance criteria for complete houses

need to be developed. The analytical models will need to include the interaction of

the various diaphragms such as shear walls,

floors, and roof, as well as inter-component

connections. Data from prior testing conNIST 3
Experimental Testing of Roof to Wall Connections in Wood Frame Houses 

4 NIST 

ducted on wood diaphragms can be used in 

the models, but as mentioned above, there 

are minimal data on the performance of inter-component connections. Therefore, experimental testing of various connections 

under monotonic and cyclic loads is necessary to characterize their performance and 

provide the necessary data for modeling. 

1.3 Scope of Current Effort 

The current research is intended to fill one 

of the gaps in the understanding of the 

structural behavior of wood frame buildings by experimentally testing two types of 

roof to wall connections to determine their 

behavior and performance. The test results 

will provide data that are now lacking, but 

are necessary to develop analytical models 

of the connections. Such models will lead to 

improved design tools for wood-frame construction, and to stronger and more structurally efficient residential buildings. 

The two types of connections tested were 

toe-nailed connections and hurricane clips. 

The simple toe-nailed connections are the 

most common type of roof to wall connection used in regions that are not routinely 

subjected to hurricanes. The hurricane clips 

are one of the lightest and simplest versions 

of a wide range of clips and straps that can 

be used to increase the strength of roof to 

wall connections. 

In the current work, the specimens were 

subjected to four types of loading. Monotonic uplift and monotonic lateral loads 

were applied to determine the general failure response curves. Combined uplift and 

lateral load, and cyclic lateral loading were 

applied to obtain specific data on how these 

connections will respond when loaded to 

failure by strong winds and seismic loads, 

respectively. 

The objectives of these tests are to understand the in-situ behavior of the wall-to-roof 

connections in the structure, explore the 

failure mechanisms, and determine the displacements and forces that occur in the individual connections. The results of the experimental tests will allow more accurate 

sub-component connection testing and lead 

to improved analytical models. 
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

2 OVERVIEW OF TEST PROGRAM

This phase of the NIST effort consisted of 2.1 Test Specimens 

experimental tests of full-scale wall-to-roof 

connections. Tests will be performed on

specimens with toe-nailed connections and

specimens with hurricane clips. The objectives of this testing were to understand the

in-situ behavior of the wall-to-roof connections in the structure, explore the failure

mechanisms, and determine the displacements and forces that occur in the individual connections, so as to allow more accurate component connection testing and

modeling in the future. 

The specimens represent a center cut

through a simple wood-frame house. Each 

specimen consisted of two 1.22 m (4 ft) long

by 2.47 m (8 ft 1.25 in) high shear walls that

supported four roof trusses with spans of

4.88 m (16 ft). A sketch of a test specimen is

shown in Figure 2.1, and a photo of one

specimen is shown in Figure 2.2 

As can be seen in Figures 2.3 and 2.4, the

framing for each shear wall consisted of

double top plates, a single bottom plate, and

Figure 2.1. Sketch of a typical test specimen. 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

four vertical studs spaced 0.40 m (16 in) on

center. All framing members were constructed from 38 mm x 89 mm (2 by 4

nominal) spruce-pine-fir, grade No. 2 lumber. The outer wall sheathing was 11 mm

(7/16 in) thick oriented strand board (OSB)

panels. These were connected to the framing with 38 mm (1.5 in) cement coated staples spaced 76 mm (3 in) on perimeter and

152 mm (6 in) on intermediate studs. 

The pre-fabricated roof trusses, which are

shown in Figure 2.4, had a top chord slope 

of 4:12, and were spaced 0.41 m (16 in)

apart. All truss elements were 38 mm x

89 mm (2 by 4 nominal) members. The roof 

sheathing consisted of 11 mm (7/16 in)

thick OSB panels attached to the trusses using 8d-common nails spaced 102 mm (4 in)

apart. 

Toe-nailed connections and hurricane clips

were used to tie the roof trusses to the shear

walls in these tests. Details about the connections are given in Section 2.1.1. 

The shear walls and roof trusses were purchased pre-fabricated from a local supplier.

They were thus fairly typical examples, in

both the material and quality, of woodframe construction in central Maryland.

The quantity, spacing, length of the staples

used to connect the OSB to the wall framing

were all standard, with respect to similar 

sized wood frame construction. The construction quality of these walls was generFigure 2.2. Typical test specimen before instrumentation. 

6 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

ally very good. The manufacturing techniques guaranteed that the quantity and

spacing of the staples was consistent. The

only aspect that was subject to human error 

and variability was the positioning of the

staples relative to the studs. While the staples were properly driven in most cases, a

few cases were observed where some of the

staples had missed a stud. 

2.1.1 Roof to Wall Connections Tested

Two types of roof to wall connections were

tested – toe-nailed connections and hurricane clips. 

For the cases of the toe-nailed connections,

each of the roof trusses were connected to

each wall using three 16d-common nails

driven at approximately a 45°angle through

the truss and into the top plate of the wall.

Two of the nails were driven into one side

of the truss, while the third nail was driven

into the other side such that the nails 

crossed at a 90° angle. 

Figure 2.3. Side view of specimen. 

For the hurricane clip connections, two nails

Figure 2.4. Front view of specimen. 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

were toe-nailed through the truss and into

the top plate of the wall for erection purposes. Then a simple, sheet metal hurricane

clip of the type shown in Figure 2.5 was

added to provide the primary load path between the truss and the walls. The standard

dimensions of the clips used are shown in

Figure 2.6. These clips were attached to the

trusses and the top plate of the wall using

four 8d common nails. 

2.2 Test Setup 

The shear walls were supported on steel

foundation frames rigidly attached to the

laboratory strong floor. The bottom plates

of each of the walls were anchored to the

foundation frames with five 12.7 mm

(1/2 in) diameter bolts, spaced 400 mm

(16 in) on center. 

The specimens were subjected to monotonic

uplift, monotonic lateral, cyclic lateral, and 

combined uplift and lateral loads. 

The uplift loads were applied using a vertical actuator with a steel load tree that distributed the load to ten points on the roof 

sheathing, as shown in Figure 2.7. The uplift point loads were further distributed using 38 mm x 184 mm (2 by 8 nominal) lumber members that were connected to the

roof sheathing, but not the trusses. These

boards spread the load over a larger area,

and prevented local failure of the sheathing. 

The lateral loads were applied using a horizontal actuator connected to a transfer 

beam, which was in turn connected to two

steel pipes that were bolted to a pair of

Figure 2.5. Hurricane clip of the type used. 

11.11 mm [7/16"]

61.91 mm [2 7/16"]

34.93 mm [1 3/8"]

107.95 mm [4 1/4"]

39.69 mm [1 9/16"]

12.7 mm [1/2"]

Figure 2.6. Dimensions of hurricane clips. 

8 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

38 mm x 184 mm (2 by 8 nominal) lumber

members that were screwed to the roof 

sheathing on either side of the ridge. This

configuration, shown in Figure 2.8, allowed

the load to be applied through the roof’s

center of mass, without applying any unusually large lateral loads to any truss

members. 

For the tests with combined lateral and uplift loads, the two loading systems were

Figure 2.7. Sketch of specimen for uplift load test 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

10 NIST

combined, as shown in Figure 2.9. 

Both the vertical and horizontal actuators

push against a steel reaction frame, which

can be seen in Figures 2.7 through 2.9. For

the uplift loads an actuator with a 152 mm

(6 in) stroke and a 222 kN (50 kip) capacity

was used, while for the lateral loads a

smaller actuator with a 152 mm (6 in) stroke

and a 45 kN (10 kip) capacity was used. 

Figure 2.8. Sketch of specimen for lateral load test 
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

2.3 Specimen Instrumentation 

The specimens were highly instrumented

with displacement transducers and load

cells to gain maximum information about 

the response characteristics of the specimens. The sensors consisted of twelve load

cells and forty-eight displacement sensors. 

The displacement sensors consisted of fortysix linear variable differential transformers

(LVDT) mounted on the specimen or one of

Figure 2.9. Sketch of specimen for combined vertical and lateral load test. 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

Table 2.1. Displacement sensors used to measure the specimen motion.

Sensor ID

Sensor

Type Stroke Length

Direction 

Measured

Reference 

Datum Sensor Location

Sensors on 1st (West Outer) Truss

SOW1XG AC LVDT 203.2 mm (8 in) East-West Absolute South wall

MIL1XG AC LVDT 203.2 mm (8 in) East-West Absolute Center of truss, lower chord 

MIU1XG AC LVDT 203.2 mm (8 in) East-West Absolute Center of truss, upper chord 

NOW1XG AC LVDT 203.2 mm (8 in) East-West Absolute North wall

Sensors on 2nd (West Inner) Truss

SOL2XR DC LVDT 50.8 mm (2 in) East-West Relative South end of truss, lower chord 

SOW2YG DC LVDT 50.8 mm (2 in) North-South Absolute South wall

SOL2YR AC LVDT 152.4 mm (6 in) North-South Relative South end of truss, lower chord 

SOL2ZRO AC LVDT 152.4 mm (6 in) Up-Down Relative South end of truss, lower chord, outside of wall

SOW2ZG AC LVDT 152.4 mm (6 in) Up-Down Absolute South wall

SOL2ZRI AC LVDT 101.6 mm (4 in) Up-Down Relative South end of truss, lower chord, inside of wall

SQL2XG AC LVDT 203.2 mm (8 in) East-West Absolute South quarter of truss, lower chord, inside of wall

SQL2ZG AC LVDT 101.6 mm (4 in) Up-Down Absolute South quarter of truss, lower chord, inside of wall

SQU2XG AC LVDT 203.2 mm (8 in) East-West Absolute South quarter of truss, upper chord, inside of wall

MIL2XG AC LVDT 203.2 mm (8 in) East-West Absolute Center of truss, lower chord 

MIL2ZG AC LVDT 101.6 mm (4 in) Up-Down Absolute Center of truss, lower chord 

NOL2XR DC LVDT 50.8 mm (2 in) East-West Relative North end of truss, lower chord 

NOW2YG AC LVDT 152.4 mm (6 in) North-South Absolute North wall

NOL2YR DC LVDT 50.8 mm (2 in) North-South Relative North end of truss, lower chord 

NOL2ZRI DC LVDT 50.8 mm (2 in) Up-Down Relative North end of truss, lower chord, inside of wall

NOW2ZG DC LVDT 50.8 mm (2 in) Up-Down Absolute North wall

NOL2ZRO AC LVDT 152.4 mm (6 in) Up-Down Relative North end of truss, lower chord, outside of wall

Sensors on 3rd (East Inner) Truss

SOL3XR DC LVDT 50.8 mm (2 in) East-West Relative South end of truss, lower chord 

SOW3YG DC LVDT 50.8 mm (2 in) North-South Absolute South wall

SOL3YR AC LVDT 152.4 mm (6 in) North-South Relative South end of truss, lower chord 

SOL3ZRO AC LVDT 152.4 mm (6 in) Up-Down Relative South end of truss, lower chord, outside of wall

SOW3ZG AC LVDT 101.6 mm (4 in) Up-Down Absolute South wall

SOL3ZRI AC LVDT 101.6 mm (4 in) Up-Down Relative South end of truss, lower chord, inside of wall

MIL3XG AC LVDT 203.2 mm (8 in) East-West Absolute Center of truss, lower chord 

MIL3ZG DC LVDT 152.4 mm (6 in) Up-Down Absolute Center of truss, lower chord 

NQL3XG AC LVDT 203.2 mm (8 in) East-West Absolute North quarter of truss, lower chord, inside of wall

NQL3ZG AC LVDT 101.6 mm (4 in) Up-Down Absolute North quarter of truss, lower chord, inside of wall

NQU3XG AC LVDT 203.2 mm (8 in) East-West Absolute North quarter of truss, upper chord, inside of wall

Sensors on 4th (East Outer) Truss

SOW4XG AC LVDT 203.2 mm (8 in) East-West Absolute South wall

SOW4YG AC LVDT 152.4 mm (6 in) North-South Absolute South wall

SOL4YR AC LVDT 152.4 mm (6 in) North-South Relative South end of truss, lower chord 

SOL4ZRO AC LVDT 152.4 mm (6 in) Up-Down Relative South end of truss, lower chord, outside of wall

SOW4ZG AC LVDT 152.4 mm (6 in) Up-Down Absolute South wall

SOL4ZRI DC LVDT 50.8 mm (2 in) Up-Down Relative South end of truss, lower chord, inside of wall

SOL4XR DC LVDT 50.8 mm (2 in) East-West Relative South end of truss, lower chord 

NOW4XG AC LVDT 203.2 mm (8 in) East-West Absolute North wall

NOW4YG AC LVDT 152.4 mm (6 in) North-South Absolute North wall

NOW4ZG DC LVDT 50.8 mm (2 in) Up-Down Absolute North wall

Sensors at corners

SWC DC LVDT 152.4 mm (6 in) Up-Down Relative South-west corner top plate 

SEC DC LVDT 101.6 mm (4 in) Up-Down Relative South-east corner top plate 

NWC DC LVDT 50.8 mm (2 in) Up-Down Relative North-west corner top plate 

NEC DC LVDT 152.4 mm (6 in) Up-Down Relative North-east corner top plate 

three reference frames located next to the

specimen. These sensors were used to

measure the displacements of the trusses

and walls, and the deformation that occurred in the roof to wall connections. 

12 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

As listed in Table 2.1, twenty-six of the sensors measured the absolute motion of the

specimen, while twenty sensors measured

the relative motion within the specimen.

Twenty-one of the sensors were used to

measure the vertical motions, and sixteen

were used to measure the lateral motion in

the east-west direction, which was the primary direction of motion during the lateral 

loading tests. The remaining nine sensors

measured out-of-plane motions in the

north-south direction. The positions of

these sensors are shown in Figure 2.10. 

Two additional LVDTs, permanently

mounted inside the hydraulic actuators,

were used to measure the displacements

applied to the specimen.

Ten strain gage-based load cells were used

to measure the uplift forces applied to the

roof of the specimen. These sensors were

Notation:

LVDT measuring absolute displacement

LVDT measuring relative displacement

Load Cell

Notation:

LVDT measuring absolute displacement

LVDT measuring relative displacement

Load Cell

Figure 2.10. Locations of displacement sensors and load cells on the specimens.

S 

E 

W 

N 

NIST 13
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

Table 2.2. Load cells used to measure the uplift loads applied to the roof sheathing. 

Sensor ID

Sensor

Type Capacity

Direction 

Measured

Reference 

Datum Sensor Location

LCS01 Load Cell 44.5 kN (10 kip) Up-Down Absolute South side, west end, outside 

LCN01 Load Cell 44.5 kN (10 kip) Up-Down Absolute North side, west end, outside 

LCS02 Load Cell 44.5 kN (10 kip) Up-Down Absolute South side, west end, inside 

LCN02 Load Cell 44.5 kN (10 kip) Up-Down Absolute North side, west end, inside 

LCS03 Load Cell 44.5 kN (10 kip) Up-Down Absolute South side, center 

LCN03 Load Cell 44.5 kN (10 kip) Up-Down Absolute North side, center 

LCS04 Load Cell 44.5 kN (10 kip) Up-Down Absolute South side, east end, inside 

LCN04 Load Cell 44.5 kN (10 kip) Up-Down Absolute North side, east end, inside 

LCS05 Load Cell 44.5 kN (10 kip) Up-Down Absolute South side, east end, outside 

LCN05 Load Cell 44.5 kN (10 kip) Up-Down Absolute North side, east end, outside 

Table 2.3. Additional sensors measured during the tests. 

Sensor ID Type Stroke or Capacity Sensor Location 

CmdVAct Command Signal 10 V Vertical actuator command signal

DispVAct AC LVDT 152.4 mm (6 in) Vertical actuator displacement

LCVAct Load Cell 222.4 kN (50 kip) Vertical actuator applied load 

CmdHAct Command Signal 10 V Horizontal actuator command signal

DispHAct AC LVDT 152.4 mm (6 in) Horizontal actuator displacement

LCHAct Load Cell 44.5 kN (10 kip) Horizontal actuator applied load 

located along the rods that transferred the

loads from the load tree to the roof sheathing. As listed in Table 2.2, each of these

load cells had a capacity of 45 kN (10 kip). 

Two additional load cells, attached to the

rods of the hydraulic actuators, were used 

to directly measure the forces generated by

the actuators. 

Table 2.3 lists the additional response signals that were recorded during testing. As

mentioned above, the forces and loads generated by each of the actuators were measured and recorded. The command signals

that were used to drive the actuators were

also monitored. Each of these signals was a

direct current voltage, with a 10 V full scale.

Since each of the actuators was driven in

displacement control, the 10 V corresponded to the maximum displacement of

the actuator. 

2.4 Test Protocols 

As described above, specimens were subjected to either monotonic uplift, monotonic

lateral, cyclic lateral, or combined uplift and

lateral loads. The loads were applied with

the actuator driven in displacement control.

During the monotonic load tests a constant

rate of deformation was applied. 

For the uplift loading tests, a number of

small deformation tests were performed to

verify that the sensors were properly measuring the response, followed by a large deformation test to fail the connections. During the first small deformation test, a vertical deformation was applied at a constant

rate of 2.54 mm/min (0.10 in/min) to a peak

of 2.54 mm (0.10 in). A second small deformation test was performed with a vertical deformation applied at a constant rate of

5.08 mm/min (0.20 in/min) to a peak of

5.08 mm (0.20 in). If the results of these initial tests appeared reasonable, the specimen

was tested to failure. During the failure 

test, the vertical deformation was applied at

a constant rate of 6.35 mm/min

(0.25 in/min), until the connections on one

side of the roof failed. 

The lateral loading test sequence was similar to the vertical test sequence. Again, a

14 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

number of small deformation tests were

performed to verify that the sensors were

working properly, followed by a large deformation test to failure. Because the 

specimens were more flexible in the lateral

direction, larger deformations and rates

were used. During the first small deformation test, the lateral deformation was applied at a constant rate of 6.35 mm/min

(0.25 in/min) to a peak of 6.35 mm (0.25 in).

During the second small deformation test,

the deformation was applied at a constant

rate of 12.7 mm/min (0.50 in/min) to a peak

of 12.7 mm (0.50 in). Again if the results of

these tests appeared to be reasonable, the

specimen was tested to failure. During the

failure test of the specimen with toe-nailed

connections, the lateral deformation was

applied at a constant rate of 12.7 mm/min

(0.50 in/min). This rate of loading resulted

in a relatively long test. So, to reduce the

test length and to make the amount of data

recorded more manageable, during the failure test of the specimen with hurricane

clips, the lateral deformation was applied at

a constant rate of 25.4 mm/min

(1.0 in/min). 

The combined lateral and uplift load tests

were performed by applying a vertical deformation at a constant rate, and calculating

in real-time the lateral deformation that

would cause a lateral load that was proportional to the load caused by the vertical deformation. Based on the shape of the truss

and the tributary area of the roof, the ratio

between the uplift load and the lateral load

that would occur during a strong windstorm was estimated as 0.295. The control

system attempted to maintain the ratios between the uplift and lateral forces at this

level throughout the test; however, due to 

limitations in the speed of the control computer, nonlinearities in the specimen response, and changes in the stiffness of the

specimen as it deformed, the actual load

ratio varied slightly over the course of each

test. As in the case of the monotonic load

test, small deformation tests were performed to validate the sensor operation.

During the failure test, the vertical deformation was applied at a rate of 6.35 mm/min

(0.25 in/min). 

The fourth test series was the cyclic lateral

loading, which was intended to simulate the

effects of earthquake motion on the connections. The applied motion was a constant

velocity (CV) deformation waveform with

increasing amplitudes over time. The generic version of this waveform is shown in 

Figure 2.11. This waveform is based on the

work of Krawinkler et al. (2001). For

application in a test, the waveform is scaled

such that the unit amplitude of the generic

waveform is equal to 60% of the deformation in a specimen subjected to monotonic

lateral loading at the point in the test after

the peak capacity has been exceeded and

the response force has dropped to 80% of

the peak value.

For the current tests, the period of the waveform was 30 s. The unit amplitude was

scaled to 37.24 mm (1.466 in) for the specimen with toe-nailed connections and to

50.19 mm (1.976 in) for the specimen with

hurricane clips. In both cases, the absolute

peak amplitude was limited to 73.7 mm

(2.90 in), due to the actuator stroke limits. 

NIST 15
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

-3.0

-2.5

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Time

Amplitude

Figure 2.11. Generic (dimensionless) lateral displacement curve for cyclic lateral load tests. 

16 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

3 RESULTS OF UPLIFT LOAD TESTS

Two specimens were tested under uplift

load to simulate the wind effects on the

structure, without any lateral component to

the load. The first specimen used the toenailed connection (three 16d-common nails) 

to tie the bottom chord of the roof trusses to 

the walls, while the second used the

stronger hurricane clip to connect the bottom chord of the trusses to the upper plate

of the walls’ top plate. 

3.1 Response with Toe-nailed Connections 

As described in section 2.4, a constantly increasing uplift deformation was applied to

the roof of the toe-nailed connection specimen at a rate of 6.35 mm/min (0.25 in/min)

for a period of approximately 360 s. This

deformation is shown in Figure 3.2 and the

resulting loads are shown in Figure 3.3. The 

specimen failed on one side at the connection between the trusses and the top plate of

the wall after about 125 s. The failure mode

was characterized as the nails withdrawing

from the top plate, which resulted in separation in the bottom wood fibers of the bottom chord as can be seen in Figure 3.1. The

specimen continued to exhibit some resistance, although the strength was relatively

small after 200 s, and continued to decrease

as all of the connections on one side of the

Figure 3.1. Failure of toe-nailed truss to wall connection.

NIST 17
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

The deformation that occurred at one of the

inner truss connections during the first test

is shown in Figure 3.9, while the deformation at three connections during the second

test is shown in Figure 3.11. The corresponding load-deformation curves are

shown in Figure 3.10 (first test) and Figure

3.12 (second test). As can be seen in these

two figures, the hurricane clip connections

showed good ductility, continuing to carry

significant, but reduced, load at relatively

large levels of deformation. 

specimen failed completely. 

Figure 3.4 shows the deformation that occurred at two connections during the test.

The outer connection, truss 4, failed first.

The drop in the deformation for this truss

occurred near the end of the test, when the 

opposite outer connection finally failed.

Truss 2 is an inner truss, and was the third

of the four connections to separate completely. The load-deformation curves for 

these two connections are shown in Figure 

3.5. 

3.3 Comparison of Responses 

3.2 Response with Hurricane Clips 

A direct comparison of the responses with

the two types of connections is shown in

Figure 3.13. The behavior of both of these

types of connections is highly nonlinear,

and once either of these connections reaches

their ultimate load they lose a significant

portion of their resistance. However, Figure

3.13 clearly shows that the hurricane clip

connection has a significantly higher uplift

capacity, and in most cases a larger failure

deformation than the toe-nailed connections. In addition, the residual strength of

the hurricane clip connection tended to be

greater than the capacity of the toe-nailed

connection. 

The specimen with the stronger hurricane

clip connections was tested twice. The first

failure occurred on the lightly instrumented

side of the specimen, and consisted of the 

entire top plate pulling loose from the wall

studs and cladding. The specimen was repaired and retested. During the second test,

failure was observed on the other side in the

walls’ top plate, as can be seen in Figure 3.6.

The hurricane clip remained attached to the

upper member of the top plate and the

truss, while the upper member of the top

plate and a portion of the lower member

separated from the rest of the wall. This

failure mode clearly illustrated the improved strength of the hurricane clip connection. 

During both tests, this specimen was loaded

in the same way as the toe-nailed connection specimen, except that the loading period was increased and, as can be seen in

Figure 3.7, the applied deformation increased proportionally. During the first

test, the connections began to lose stiffness

after about 150 s, but they did not fail until

approximately 225 s. Due to the nature of

the failure, the resistance of the specimen

dropped by about half when the first failure 

occurred. This response can be observed in 

Figure 3.8. 

18 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0 50 100 150 200 250 300 350 400 450 500

Time (seconds)

Displacement (

m

m)

Figure 3.2. Vertical displacement applied to specimen with toe-nailed connections. 

0

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30000

0 50 100 150 200 250 300 350 400 450 500

Time (seconds)

Force (N)

0.0

10.0

20.0

30.0

40.0

50.0

60.0

Displacement (

m

m)

Actuator Load

Commanded Displacement

Figure 3.3. Vertical load applied to specimen with toe-nailed connections. 

NIST 19
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400 450 500

Time (seconds)

Displacement (m

m)

Truss 2

Truss 4

Commanded Displacement

Figure 3.4. Connection deformation response of specimen with toe-nailed connections. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10.0 0.0 10.0 20.0 30.0 40.0 50.0

Displacement (mm)

Force (N)

Truss 2

Truss 4

Figure 3.5. Load-deformation response of specimen with toe-nailed connections. 

20 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

Figure 3.6. Failure of hurricane clip connection.

NIST 21
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0.0

10.0

20.0

30.0

40.0

50.0

60.0

0 50 100 150 200 250 300 350 400 450 500

Time (seconds)

Displacement (mm)

Figure 3.7. Vertical displacement applied to specimen with hurricane clips. 

0

5000

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20000

25000

30000

0 50 100 150 200 250 300 350 400 450 500

Time (seconds)

Force (N)

0.0

10.0

20.0

30.0

40.0

50.0

60.0

Displacement (m

m)

Actuator Load

Commanded Displacement

Figure 3.8. Vertical load applied to specimen with hurricane clips.

22 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400 450 500

Time (seconds)

Displacement (m

m)

Truss

Commanded Displacement

Figure 3.9. Connection deformation response of first test with hurricane clips. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10.0 0.0 10.0 20.0 30.0 40.0 50.0

Displacement (mm)

Force (N) Figure 3.10. Load-deformation response of first test with hurricane clips.

NIST 23
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350 400 450 500

Time (seconds)

Displacement (m

m)

Truss 2

Truss 3

Truss 4

Commanded Displacement

Figure 3.11. Connection deformation response of second test with hurricane clips. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10.0 0.0 10.0 20.0 30.0 40.0 50.0

Displacement (mm)

Force (N)

Truss 2

Truss 3

Truss 4

Figure 3.12. Load-deformation response of second test with hurricane clips. 

24 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10.0 0.0 10.0 20.0 30.0 40.0 50.0

Displacement (mm)

Force (N)

Toe-nailed

Hurricane Clip

Figure 3.13. Comparison of responses with toe-nailed connections and hurricane clips. 

NIST 25
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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26 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

4 RESULTS OF MONOTONIC LATERAL LOAD TESTS

Two specimens were tested with a monotonic lateral load to determine the ultimate

shear capacity of the connections and their

pushover response. As in the case of the

monotonic uplift tests, in one specimen the

bottom chord of each roof truss was connected to the walls with toe-nailed connection, while in the other specimen hurricane

clips were used. 

4.1 Response with Toe-nailed Connections 

For the specimen with toe-nailed connections, the lateral deformation was applied at

a constant rate of 12.7 mm/min

(0.50 in/min) for a period of about 330 s, as

can be observed in Figure 4.2. The resulting

load is shown in Figure 4.3. The specimen

resisted the applied load with constantly

decreasing stiffness, until about 270 s into

the test. At this point, the tension, due to

the overturning moments, in the connections at one end caused the outer truss to

pull free of the top plate. This failure can be

seen in Figure 4.1. As in the case of the uplift loading, the failure mode can be characterized as nail withdrawal from the top

plate. This failure resulted in the wood

splitting in the bottom chord of one inner

truss, but little damage to the wood of the

outer truss. 

The lateral deformations in the toe-nailed

connections of three of the trusses are

shown in Figure 4.4, while the uplift deformations in the same connections are shown 

in Figure 4.5. From these results it is clear

that the connections were quite stiff in

shear, but more flexible in tension. The corresponding force displacement responses

are shown in Figures 4.6 and 4.7. The responses of all three connections were quite

similar in shear, but the outer connection,

which failed first, was clearly carrying

greater tension due to the overturning moments. 

The lateral and vertical components of the

response of the east inner truss are shown

in Figure 4.8. These curves clearly show a

difference in the lateral and vertical stiffness

of the connection, and how much more deformation occurred in the vertical direction

than the lateral. Figure 4.9 shows the same

response for the east outer truss. In this

case the difference in the stiffnesses before

failure is not as great, but again the vertical

deformation is much greater than the lateral

deformation. It is notable that the peak vertical load carried by this connection is

nearly as large as the load carried by the

toe-nailed connections tested with uplift

loading.

4.2 Response with Hurricane Clips 

For the specimen with hurricane clips, the

lateral deformation was applied at a constant rate of 25.4 mm/min (1.0 in/min) for a

period of about 250 s, as can be observed in

Figure 4.11. The load that resulted is shown

in Figure 4.12. The specimen resisted the

applied load with a near constant stiffness,

until about 170 s into the test. At this point,

the outer truss pulled free of the top plate.

As in the case of the toe-nailed connections,

the tension due to the overturning moments

appeared to play a major role in the failure,

which can be seen in Figure 4.10. Also as in

the prior test, the failure mode can be characterized as nail withdrawal from the top

plate. 

The lateral deformations in the connections

of three of the trusses are shown in Figure

4.13, and the uplift deformations in these

connections are shown in Figure 4.14. From

these results it is clear that like the toenailed connections, the hurricane clip conNIST 27
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

nections were quite stiff in shear, but relatively flexible in tension. The corresponding force displacement responses are shown

in Figures 4.15 and 4.16. Again, the responses of all three connections were quite

similar in shear, but the outer connection,

which failed first, was clearly carrying

greater tension due to the overturning moments, and the westernmost connection

never reached its failure capacity. 

Figure 4.17 shows the lateral and vertical

components of the response of the east inner truss. These curves clearly show a difference in the lateral stiffness of the connection was greater than the vertical stiffness,

and how much more deformation occurred 

in the vertical direction than the lateral.

Figure 4.18 shows the same response for the

east outer truss. In this case, the stiffnesses

are similar to the inner truss, and again the

vertical deformation is much greater than

the lateral deformation. While the peak vertical load carried by this connection is

nearly twice as large as the peak lateral

load, it is somewhat smaller than the load

carried by the hurricane clip connections

tested with uplift loading. One reason for

this last result may be the difference in the

failure modes between the two tests. 

Figure 4.1. Failure of toe-nailed connection with lateral load. 

28 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

20

40

60

80

100

120

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (

m

m)

Figure 4.2. Lateral displacement applied to specimen with toe-nailed connections. 

-16000

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0

2000

0 50 100 150 200 250 300 350

Time (seconds)

Force (N)

0

20

40

60

80

100

120

Displacement (

m

m)

Actuator Load

Actuator Displacement

Figure 4.3. Lateral load applied to specimen with toe-nailed connections.

NIST 29
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

-100

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-70

-60

-50

-40

-30

-20

-10

0

10

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (m

m)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.4. Lateral displacement responses for trusses with toe-nailed connections. 

-10

0

10

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30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (m

m)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.5. Uplift displacement responses for trusses with toe-nailed connections. 

30 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

-5000

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-500

0

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10

Displacement (mm)

Force (N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.6. Lateral force-displacement responses for trusses with toe-nailed connections. 

0

500

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1500

2000

2500

3000

3500

4000

4500

5000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.7. Uplift force-displacement responses for trusses with toe-nailed connections. 

NIST 31
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

500

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2500

3000

3500

4000

4500

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-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (N)

Horizontal

Vertical

Figure 4.8. Comparison of lateral and vertical responses for inner truss with toe-nailed connections. 

0

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-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (N)

Horizontal

Vertical

Figure 4.9. Comparison of lateral and vertical responses for outer truss with toe-nailed connections. 

32 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

4.3 Comparison of Responses 

A direct comparison of the responses at the

inner trusses with the two types of connections is shown in Figure 4.19, while the responses at the outer trusses are shown in

Figure 4.20. The behavior of both of these

types of connections is highly nonlinear,

with most of the deformation occurring in 

the vertical direction. These figures clearly

show that the hurricane clip connections

have a significantly higher capacity for both

uplift and shear. As in the case of the

monotonic uplift loading, the residual

strength of the hurricane clip connection

tended to be similar to or greater than the

capacity of the toe-nailed connection. 

Figure 4.10. Failure of hurricane clip connection with lateral load. 

NIST 33
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

20

40

60

80

100

120

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (

m

m) Figure 4.11. Lateral displacement applied to specimen with hurricane clips 

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0 50 100 150 200 250 300 350

Time (seconds)

Force (N)

0

20

40

60

80

100

120

Displacement (

m

m)

Actuator Load

Actuator Displacement

Figure 4.12. Lateral load applied to specimen with hurricane clips 

34 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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0

10

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (mm)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.13. Lateral displacement responses for trusses with hurricane clips. 

-10

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10

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30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (mm)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.14. Uplift displacement responses for trusses with hurricane clips. 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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0

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10

Displacement (mm)

Force (N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.15. Lateral force-displacement responses for trusses with hurricane clips. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10 0 10 20 30 40 50 60 70 80 90

Displacement (mm)

Force (

N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 4.16. Uplift force-displacement responses for trusses with hurricane clips. 

36 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

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1500

2000

2500

3000

3500

4000

4500

5000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

N)

Horizontal

Vertical

Figure 4.17. Lateral and vertical responses for inner truss with hurricane clips. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

N)

Horizontal

Vertical

Figure 4.18. Lateral and vertical responses for outer truss with hurricane clips. 

NIST 37
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (N)

Toe-nailed - Horizontal

Toe-nailed - Vertical

Hurricane Clip - Horizontal

Hurricane Clip - Vertical

Figure 4.19. Comparison of responses of inner trusses. 

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

N)

Toe-nailed - Horizontal

Toe-nailed - Vertical

Hurricane Clip - Horizontal

Hurricane Clip - Vertical

Figure 4.20. Comparison of responses of outer trusses. 

38 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

5 RESULTS OF CYCLIC LATERAL LOAD TESTS

The corresponding uplift deformations in 

the connections are shown in Figure 5.5.

From these results it is clear that the connections were more flexible in tension, and that

both the outer truss connection on the south

side and the inner truss connection on the

north side began to deform more than the

other connections after about 600 s. 

Two specimens were tested with a cyclic

lateral load to determine their response to

an earthquake type loading. Again in one

specimen the bottom chords of the roof 

trusses were connected to the walls with

toe-nailed connections, while in the other

specimen hurricane clips were used. 

5.1 Response with Toe-nailed Connections The corresponding force-displacement responses are shown in Figures 5.6 and 5.7.

The responses of all four connections exhibit significant hysteresis, indicating that

these connections would dissipate a significant amount of seismic energy before failure. For all connections except the east

outer truss connection, the envelopes of the

lateral and uplift responses during this test

were similar to the responses observed during the monotonic lateral load test. However, the east connection on the outer truss

exhibited more lateral deformation and less

lateral stiffness than the other connections,

while carrying more vertical load than was

typical in prior tests. 

For the specimen with toe-nailed connections, the waveform described in section 2.4,

was applied with a cycle period of 30 s and

the unit amplitude of the generic waveform

scaled to 32.24 mm (1.466 in). The resulting

displacement curve is shown in Figure 5.2,

and the resulting load is shown in Figure

5.3. Although the specimen’s stiffness decreased during the test, the specimen resistance continued to increase until the final

large cycle of motion, about 1220 s into the

test. At this point, the connections at tension end of the specimen pulled free of the

top plate. This failure can be seen in Figure

5.1. As in the case of the previous tests with

the toe-nailed connections, the failure was

due to the nails withdrawing from the top

plate. This failure resulted in some wood

splitting in the top plate of the wall, but little damage to the wood of the trusses. 

5.2 Response with Hurricane Clips 

For the specimen with hurricane clips, the

waveform described in section 2.4, was applied with a cycle period of 30 s and the unit

amplitude of the generic waveform scaled

to 50.19 mm (1.976 in), as can be observed in

Figure 5.8. The load that resulted is shown

in Figure 5.9. The specimen resisted the applied load with some degradation in stiffness, but increasing resistance, until the last

large deformation cycle, which occurred

approximately 1220 s into the test. At this

point the specimen’s north wall began to

fail at the sill plate, with the studs and cladding pulling free of the sill. The hurricane

clip connections had not yet failed when the 

test was stopped. 

The lateral deformations in the toe-nailed

connections of four connections for three of

the trusses are shown in Figure 5.4. Note

that the failure occurred on the north side of

the specimen, so three of the four curves

represent the non-failing response. From

this figure it can be noted that the outer

truss connection on the south side, which

did not completely fail, began to deform

significantly after about 600 s. The inner

truss connection on the north side had relatively moderate shear deformations until

the last cycle before it failed. 

NIST 39
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

The lateral deformations in the connections

of three of the trusses are shown in Figure

5.10, and the uplift deformations in these

connections are shown in Figure 5.11.

While none of the connections failed, the

responses shown in Figure 5.10 clearly indicate that the connection in the east inner

truss may have begun to fail at about 950 s

into the test. Based on the responses shown

in both figures, it is clear that, as in the

monotonic lateral load test, the hurricane

clip connections were quite stiff in shear,

but relatively flexible in tension. 

The corresponding force displacement responses are shown in Figures 5.12 and 5.13.

As in the case of the toe-nailed connections,

the responses of all four connections shown

in these figures exhibit significant hysteresis. The east inner truss connection, which

may have begun to fail early in the test, had

the largest hysteresis. All of the connections

responses had envelopes that were similar

to the responses observed during the monotonic lateral load test. Since none of the

connections failed entirely, the ultimate

load capacity for the connections with this

type of loading was not determined. However, it is clear for this load case the hurricane clips were stronger than the wall itself. 

Figure 5.1. Failure of toe-nailed connection with cyclic load. 

Failed connections

40 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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0

20

40

60

80

0 200 400 600 800 1000 1200

Time (seconds)

Displace

ment (

m

m)

Figure 5.2. Lateral displacement applied to specimen with toe-nailed connections. 

-15000

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0

5000

10000

15000

0 200 400 600 800 1000 1200

Time (seconds)

Force (N)

-80

-60

-40

-20

0

20

40

60

80

Displacement (

m

m)

Load

Actuator Displacement

Figure 5.3. Lateral load applied to specimen with toe-nailed connections.

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

0 200 400 600 800 1000 1200

Time (seconds)

Displacement (

m

m)

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.4. Lateral displacement responses for trusses with toe-nailed connections. 

-2

0

2

4

6

8

10

12

14

16

18

0 200 400 600 800 1000 1200

Time (seconds)

Displacement (

m

m)

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.5. Uplift displacement responses for trusses with toe-nailed connections. 

42 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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0

1000

2000

3000

4000

5000

-5.0 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0

Displacement (mm)

Force (N)

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.6. Lateral force-displacement responses for trusses with toe-nailed connections. 

-5000

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0

1000

2000

3000

4000

5000

-2 0 2 4 6 8 10 12 14 16 1

Displacement (mm)

Force (

N)

8

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.7. Uplift force-displacement responses for trusses with toe-nailed connections. 

NIST 43
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

-80

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-40

-20

0

20

40

60

80

0 200 400 600 800 1000 1200

Time (seconds)

Displace

ment (

m

m) Figure 5.8. Lateral displacement applied to specimen with hurricane clips. 

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0

5000

10000

15000

0 200 400 600 800 1000 1200

Time (seconds)

Force (N)

-80

-60

-40

-20

0

20

40

60

80

Displacement (

m

m)

Load

Actuator Displacement

Figure 5.9. Lateral load applied to specimen with hurricane clips.

44 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

-5.0

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

0 200 400 600 800 1000 1200

Time (seconds)

Displacement (

m

m)

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.10. Lateral displacement responses for trusses with hurricane clips. 

-2

0

2

4

6

8

10

12

14

16

18

0 200 400 600 800 1000 1200

Time (seconds)

Displacement (

m

m)

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.11. Uplift displacement responses for trusses with hurricane clips. 

NIST 45
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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0

1000

2000

3000

4000

5000

-5.0 -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0

Displacement (mm)

Force (N)

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.12. Lateral force-displacement responses for trusses with hurricane clips. 

-5000

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0

1000

2000

3000

4000

5000

-2 0 2 4 6 8 10 12 14 16 1

Displacement (mm)

Force (

N)

8

West Inner Truss - North

West Inner Truss - South

East Inner Truss

East Outer Truss

Figure 5.13. Uplift force-displacement responses for trusses with hurricane clips. 

46 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses 

NIST 47 

5.3 Comparison of Responses 

A direct comparison of the results is difficult, because the hurricane clip connection 

did not completely fail. As was the case 

with the monotonic lateral load, the behavior of both of these types of connections is 

highly nonlinear, which lead to significant 

hysteresis in the response. This hysteresis 

will help to provide significant energy dissipation during seismic events. The results 

show that the hurricane clip connections 

have a higher capacity to withstand such 

loading, but how much greater the capacity 

is could not be determined. 
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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48 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

6 RESULTS OF COMBINED UPLIFT AND LATERAL LOAD TESTS

The final two specimens were tested with a

combined uplift and lateral load to simulate

the wind effects on the structure, including

a lateral load component due to pressure on

the outside walls. As describe in section 2.4,

a constant uplift deformation was applied

to the roof at a rate of 6.35 mm/min

(0.25 in/min). At the same time the applied

vertical load was measured, and a lateral 

displacement applied to produce a lateral 

load equal to 29.5% of the vertical load.

Limitations in the speed of the control computer and the highly nonlinear nature of the

specimens limited the accuracy of the lateral

loads as the displacements became large,

but generally the peak lateral loads were

about 25% of the peak vertical loads. The

same loading sequence was used for both

specimens. 

6.1 Response with Toe-nailed Connections 

The two deformations applied to the specimen with toe-nailed connections are shown

in Figure 6.2. The resulting loads are shown

in Figure 6.3. As in the previous tests, the

specimen’s stiffness decreased throughout

the test, but the resistance continued to increase until connections began to fail about

250 s into the test. At this point the nails in

the connection that was being placed in tension by the overturning moment from the

lateral portion of the load pulled free from 

the top plate of the wall, as shown in Figure

6.1. This failure resulted in some wood

splitting in the top plate of the wall, but little other damage to the material. 

The lateral deformations in the toe-nailed

connections of three of the trusses are

shown in Figure 6.4 and the uplift deformations in the same connections are shown in

Figure 6.5. The corresponding force displacement responses are shown in Figures

6.6 and 6.7. The responses of all three connections were quite similar in both shear

and tension, although the outer connection,

which failed first, was carrying slightly

more tension, due to the overturning moments caused by the lateral load. 

The lateral and vertical components of the

response of the east inner truss are shown

in Figure 6.8, while Figure 6.9 shows the

same response for the east outer truss. 

These curves clearly show that during this

test there was little difference in the initial

lateral and vertical stiffnesses of the connection. The curves also illustrate how much

more deformation occurred in the vertical 

direction than the lateral. The peak vertical

loads carried by these connections were

greater than the loads carried by similar

connections subjected to uplift loading

alone. 

6.2 Response with Hurricane Clips 

The two deformations applied to the specimen with hurricane clips are shown in

Figure 6.11, and the applied loads are

shown in Figure 6.12. As was the case in

the monotonic lateral load test, the specimen resisted the applied load with a near 

constant stiffness, until the first connection

began to fail at about 180 s into the test. The

failure occurred at the connection on the

outer truss that was in tension from both

the uplift and the overturning moment due

to the lateral load. The failure consisted of

the top plate of the wall splitting, which allowed the hurricane clip to pull free, as can

be seen in Figure 6.10. The connection of

the inner truss next to the one that failed

first, failed by the nails withdrawing from

the intact top plate. 

The lateral deformations in the connections

of three of the trusses are shown in Figure

NIST 49
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

Figure 6.17 shows the lateral and vertical

components of the response of the east inner truss. These curves clearly show that

the initial lateral and vertical stiffnesses of

the connection were nearly equal, and how

much more deformation occurred in the

vertical direction than the lateral. Figure 

6.18 shows the same response for the east

outer truss. In this case, both of the

connection stiffnesses are much less than

those of the inner truss. As mentioned

above, the outer truss connection failed at a

relatively small load, and the deformations

at failure were much greater than for the

other conn

6.13, and the uplift deformations in these

connections are shown in Figure 6.14. The

corresponding force displacement responses are shown in Figures 6.15 and 6.16.

Again, the responses of the two inner

connections were quite similar, but the

outer connection, which failed first,

exhibited much less stiffness in both shear

and uplift, and failed at a relatively low

load. In fact, the capacity of this connection

was only slightly greater than the toe-nailed

connections and much less than other

hurricane clip connections. The reduced

capacity may have been due to an inherent

weakness in the wood of the top plate, or a

split in the wood caused by a poorly driven

nail. 

ections. 

Figure 6.1. Failure of toe-nailed connection with combined load. 

50 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

10

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30

40

50

60

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (

m

m)

Lateral

Vertical

Figure 6.2. Displacements applied to specimen with toe-nailed connections. 

0

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0 50 100 150 200 250 300 350

Time (seconds)

Force (N)

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10

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60

Displacement (

m

m)

Lateral Load (inverted)

Vertical Load

Lateral Actuator Displacement

Vertical Actuator Displacement

Figure 6.3. Loads applied to specimen with toe-nailed connections. 

NIST 51
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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-20

-10

0

10

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (m

m)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.4. Lateral displacement responses for trusses with toe-nailed connections. 

-10

0

10

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30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (m

m)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.5. Uplift displacement responses for trusses with toe-nailed connections. 

52 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

-7500

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-5500

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-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10

Displacement (mm)

Force (N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.6. Lateral force-displacement responses for trusses with toe-nailed connections. 

0

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3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70

Displacement (mm)

Force (N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.7. Uplift force-displacement responses for trusses with toe-nailed connections. 

NIST 53
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

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3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

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Horizontal

Vertical

Figure 6.8. Lateral and vertical responses for inner truss with toe-nailed connections. 

0

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2000

3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (N)

Horizontal

Vertical

Figure 6.9. Lateral and vertical responses for outer truss with toe-nailed connections. 

54 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

6.3 Comparison of Responses 

A direct comparison of the responses at the

east inner trusses with the two types of

connections is shown in Figure 6.19, while

the responses for the outer trusses are

shown in Figure 6.20. The behavior of the

inner trusses matches the behavior seen in

other loading cases, with the hurricane clips

providing a much greater capacity than the

toe-nailed connections. However, as discussed above, and clearly visible in Figure

6.20, the outer truss hurricane clip connection that failed when the top plate of the 

wall split provided only a slightly greater

capacity than the toe-nailed connection.

These curves highlight the great variability

that can occur in the response of wood

frame construction, due to both the variability in the materials and in the quality of

workmanship. Note, however, that the

overall strength of the specimen was not

greatly compromised by the weak outer

connection. The combined strength of the

other three hurricane clips on that wall of 

the specimen allowed the specimen to resist

almost 45% more load than the specimen

with toe-nailed connections. 

Figure 6.10. Failure of hurricane clip connection with combined load. 

NIST 55
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

10

20

30

40

50

60

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (

m

m)

Lateral

Vertical

Figure 6.11. Displacements applied to specimen with hurricane clips. 

0

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25000

30000

35000

0 50 100 150 200 250 300 350

Time (seconds)

Force (N)

0

10

20

30

40

50

60

Displacement (

m

m)

Lateral Load (inverted)

Vertical Load

Lateral Actuator Displacement

Vertical Actuator Displacement

Figure 6.12. Loads applied to specimen with hurricane clips. 

56 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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-30

-20

-10

0

10

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (m

m)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.13. Lateral displacement responses for trusses with hurricane clips. 

-10

0

10

20

30

40

50

60

70

80

90

100

0 50 100 150 200 250 300 350

Time (seconds)

Displacement (m

m)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.14. Uplift displacement responses for trusses with hurricane clips. 

NIST 57
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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-6500

-5500

-4500

-3500

-2500

-1500

-500

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10

Displacement (mm)

Force (N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.15. Lateral force-displacement responses for trusses with hurricane clips. 

0

1000

2000

3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

N)

West Inner Truss

East Inner Truss

East Outer Truss

Figure 6.16. Uplift force-displacement responses for trusses with hurricane clips. 

58 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

1000

2000

3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (N)

Horizontal

Vertical

Figure 6.17. Lateral and vertical responses for inner truss with hurricane clips. 

0

1000

2000

3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (N)

Horizontal

Vertical

Figure 6.18. Lateral and vertical responses for outer truss with hurricane clips. 

NIST 59
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

0

1000

2000

3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

N)

Toe-nailed - Horizontal

Toe-nailed - Vertical

Hurricane Clip - Horizontal

Hurricane Clip - Vertical

Figure 6.19. Comparison of responses of inner trusses. 

0

1000

2000

3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60 70 80 90 100

Displacement (mm)

Force (

N)

Toe-nailed - Horizontal

Toe-nailed - Vertical

Hurricane Clip - Horizontal

Hurricane Clip - Vertical

Figure 6.20. Comparison of responses of outer trusses. 

60 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

7 CONCLUSIONS

Recent disasters in the United States have

resulted in few casualties, but they have

caused substantial damage and significant

economic loss to residential housing. An

investigation of the state-of-the-art in experimental and analytical research on

wood-frame housing found that while significant progress has been made in analytical modeling and testing of shear walls and

diaphragms, only limited progress has been

made on the testing and modeling of complete houses and inter-component connections. 

The research reported herein attempts to

help improve the performance of woodframe housing by filling one of the gaps in

the understanding of the structural behavior of wood frame buildings subjected to

extreme loads. This work consisted of experimentally testing two types of roof to

wall connections to determine their performance and to provide the data, which

are now lacking but are necessary for the

future development of analytical models of 

the connections and for complete 3-D numerical models of entire houses. Such models will lead to improved design tools for

wood-frame construction, and to stronger

and more structurally efficient residential

buildings. 

The two types of connections tested included toe-nailed connections and hurricane clips. The simple toe-nailed connections represent the most common type of 

roof to wall connection in areas that are not

routinely subjected to hurricanes. The hurricane clips represent the lightest and simplest version of a wide range of clips and

straps that can be used to increase the

strength of roof to wall connections. 

The specimens with these connections were

subjected to four types of loading: monotonic uplift, monotonic lateral load or pushover, combined uplift and lateral load, and

cyclic lateral loading. The first two load

types provide general failure response

curves, while the third and fourth load

types provide specific data on how these

connections will respond when loaded to

failure by strong winds and seismic loads,

respectively. 

The results of the monotonic uplift load test

showed that the behavior of both types of

connections tested is nonlinear under this

form of load. The results also showed that

once either of these connections reaches

their ultimate load they lose a significant

portion of their resistance. However, the

hurricane clip connection had a significantly

higher uplift capacity, and in most cases a

larger failure deformation than the toenailed connections. The results showed that

the residual strength of the hurricane clip

connection tended to be greater than the

capacity of the toe-nailed connection. 

The tests with monotonic lateral loading

showed that the behavior of both of these

types of connections tended to be stiffer in

shear than in tension (or uplift). Because 

the loads on the individual connections

were a combination of shear and uplift,

with the uplift caused by overturning moments in the specimen, the performance of

the specimens in pure shear was not observed. However, the performance with a

realistic combination of shear and uplift indicated that the uplift component tended to

govern the failure of the connections. The

results clearly show that the hurricane clip

connections have a significantly higher capacity for both uplift and shear than the toenailed connections. As was the case with

the monotonic uplift loading, the residual

strength of the hurricane clip connections

tended to be similar to or greater than the

NIST 61
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

ultimate capacity of the toe-nailed connections. 

Tests with a cyclic lateral displacement

were performed to assess the performance

and behavior of the connections when subjected to seismic loads. While the toe-nailed

connections failed after numerous cycles,

the hurricane clips proved to be stronger

than other components of the specimen.

The hurricane clips were still intact when

the wall studs and cladding began to separate from the base plate. As was the case

with the monotonic loads, the behavior of

both types of connections was nonlinear,

which produced significant hysteresis in the

response. Such hysteresis can provide

significant energy dissipation during

seismic events. The results indicated that

the hurricane clip connections have a higher

capacity to withstand seismic loading, but

the magnitude of the increased capacity

could not be determined.

Finally, tests were performed with combined uplift and lateral loading to determine the performance and behavior of the

connections when subjected to strong

winds. During the test with hurricane clip

connections one of the connections failed at

a relatively low load when the top plate of

the wall split where the connection was anchored. The load at which this connection

failed was still slightly larger than the loads

at which the toe-nailed connections failed.

The behavior of the other hurricane connections was similar to the behavior seen in

other loading cases, with the hurricane clips

providing a much greater capacity than the

toe-nailed connections. This response highlights the great variability that can occur in

the response of wood frame construction,

due to both the variability in the materials

and in the quality of workmanship. However, the overall strength of the hurricane

clip specimen was not greatly compromised

by the single weak connection. The combined strength of the other three hurricane

clips on that wall of the specimen allowed

the specimen to resist almost 45% more load

than the specimen with toe-nailed connections. 

The most important conclusion that can be

reached from this effort is the great improvement in performance that was gained

when using the hurricane clips instead of

the toe-nailed connections. These simple

clips tended to increase capacity by more

than 40%. As observed in the cyclic loading

tests, the hurricane clip connections had

strengths that were similar to the strength

of the walls themselves. Further increases

in the connection capacity would require

clips or straps that connect the trusses directly to the wall studs, and should probably be paired with straps that anchor the

studs directly to the foundation. 

There is, unfortunately, a significant uncertainty associated with these results. Due to

the limited number of tests and specimens,

a statistical analysis of the results and an

accurate determination of their uncertainty

are not practical. In general, there is a large

variation in the response of wood-frame

housing components due to variations in

the material properties of the wood members and inconsistencies in the quality of

construction. The wood properties can vary

considerably, and are dependent on the

wood type, dryness, and density, as well as

cracks or other physical defects. The quality

of construction can vary considerably depending on the experience and skill of the

builders. The uncertainty of the results between test specimens was minimized by

purchasing all materials at the same time

and from the same distributor, and having

the walls and roof trusses pre-fabricated. In

addition, the same two people performed 

the final assembly of all of the specimens.

Although the individual results have some

uncertainty, the general trends in the over62 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

all performance were quite consistent and

the uncertainty of the relative response between the specimens with toe-nailed connection and those with hurricane clips is

estimated to be small. 

The data obtained in these tests can provide

the basis for limited analytical models of the

connection response. Additional testing is

required to fully quantify the response of

roof to wall connections. Some gaps that

still need to be filled include tests of additional types of connections and tests of

specimens with longer wall lengths. Component tests of single, directly loaded connections would allow numerous tests with a

particular load pattern and connection type,

to determine the statistical mean, variance,

and uncertainty of the response. Tests of

wall-to-foundation and wall-to-wall connections are also necessary to fully determine

the response of wood-frame construction. 

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Experimental Testing of Roof to Wall Connections in Wood Frame Houses

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64 NIST
Experimental Testing of Roof to Wall Connections in Wood Frame Houses

8 REFERENCES

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