Engineering Properties 

of Douglas-fir Lumber 

Reclaimed from 

Deconstructed Buildings

Robert H. Falk

Derek G. Maul

Steven M. Cramer 

James Evans

Victoria Herian

United States

Department of

Agriculture

Forest Service

Forest

Products

Laboratory

Research

Paper

FPL–RP–650
July 2008

Falk, Robert H.; Maul, Derek G.; Cramer, Steven M.; Evans, James; 

Herian, Victoria. 2008. Engineering properties of douglas-fir lumber 

reclaimed from deconstructed buildings. Research Paper FPL-RP-650. 

Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 47 p.

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Abstract

A vast wood resource exists in our Nation’s wood-framed 

building infrastructure. As the buildings in this infrastructure 

age and are remodeled or removed for redevelopment, the 

wood framing residing in these buildings has the potential to 

be recovered for reuse. However, little technical information 

exists on the residual engineering properties of reclaimed 

dimensional lumber. 

Our study was undertaken to quantify the engineering 

strength and stiffness of dimensional Douglas-fir 2-by lumber recovered from building dismantlement or deconstruction. These data can serve as a basis for establishing formal 

recognition of this resource in current grading rules and 

engineering design standards.

Keywords: lumber, salvaged, reclaimed, deconstruction, 

engineering properties

Acknowledgments

Over the course of the several years of this research project, 

many people have been contributing efforts toward its 

completion. The Engineering Mechanics Laboratory staff at 

the U.S. Forest Service, Forest Products Laboratory (FPL) 

contributed greatly, including Bill Nelson, Tim Nelson, and 

Bob Edlund. FPL statistics staff members James Evans and 

Victoria Herian provided important statistical advice and 

analysis. West Coast Lumber Inspection Bureau (WCLIB) 

Grading Supervisors Bob Johnson, Tom Bigham, and Jerry 

Hames brought many decades of lumber-grading experience 

to the project and had many valuable suggestions about the 

reuse of salvaged lumber. 

Conversion table 

To convert from To Multiply by 

inch (in.) millimeter (mm) 25.4 

foot (ft) meter (m) 0.3048 

lb/in2 pascal (Pa) 6.8948 ×103

acre ha 0.4047 

English unit Formula SI unit 

temperature (°F) [ TF – 32]/1.8 temperature (°C) 

Billion and trillion are used as defined in the U.S. System as 109

and 1012, respectively. 

Contents

Page

Executive Summary............................................................. i

Background.......................................................................... 1

 Lumber Grading............................................................... 1

 Previous Research............................................................ 2

Selection of Lumber for Testing .......................................... 2

 Locations.......................................................................... 2

Grading Tested Lumber ....................................................... 4

 Species Identification....................................................... 5

 Moisture Content ............................................................. 5

Testing Methodologies......................................................... 5

 Full Size Bending............................................................. 5

 Small Clear Bending........................................................ 6

Test Results.......................................................................... 7

 Small Clear Results.......................................................... 7

 Small Clear Specimens.................................................... 7

 Property Relationships..................................................... 8

Full-Size Lumber ............................................................... 10 

Property Comparisons........................................................ 11

 Distributions................................................................... 11

 Size Effect...................................................................... 12

 Comparison to Other Data ............................................. 16

 In-Grade Comparison..................................................... 16

Analysis of Full-Size Lumber by Size and Grade ............. 17 

Location and Member Type ............................................... 17 

Lumber Damage................................................................. 23

 Damage Categories........................................................ 35

Full-Size Lumber Failure Types ........................................ 38

 No. 2 Grade.................................................................... 38 

Select Structural Grade ...................................................... 40

Analysis of Full-Size Lumber by Grade ............................ 43

Conclusions........................................................................ 44

 Clear Wood Properties................................................... 44

 Full-Size Lumber Properties.......................................... 44

Recommendations.............................................................. 45

References.......................................................................... 45

Appendix—Reclaimed Lumber Test Worksheet................ 47

Conversion table 

To convert from To Multiply by 

inch (in.) millimeter (mm) 25.4 

foot (ft) meter (m) 0.3048 

lb/in2 pascal (Pa) 6.8948 ×103

acre ha 0.4047 

English unit Formula SI unit 

temperature (°F) [ TF – 32]/1.8 temperature (°C) 

Billion and trillion are used as defined in the U.S. System as 109

and 1012, respectively. 
Executive Summary

Background

A vast wood resource exists in our Nation’s wood-framed 

building infrastructure. When buildings or other wood structures reach the end of their useful life, the structural lumber 

and timber can be salvaged and reused in new construction 

and remodeling. Little technical information exists on the 

residual engineering properties of this lumber. To what extent the damage found in reclaimed lumber (resulting from 

original construction, a lifetime of use, and the dismantlement process) affects lumber strength has not been 

quantified.

Objective

The primary objective of this paper is to quantify the engineering properties (most importantly bending strength and 

stiffness) of full-size 2-by lumber reclaimed from buildings 

slated for demolition. This paper also documents lumber 

clear-wood strength as well as the effect of various forms 

of damage on lumber bending strength, including edge-nail 

holes, face-nail holes, and splits.

Procedures

Lumber was salvaged from buildings to be demolished at 

four different locations. The collected lumber was graded 

on-site by a lumber grading supervisor. Two grades (Select 

Structural and No. 2) of three sizes (2 by 6; 2 by 8; and 

2 by 10) were returned to the Forest Products Laboratory, 

Madison, Wisconsin, for laboratory testing. Several 

thousand pieces of lumber were graded to yield the 

1,078 full-size pieces tested. This lumber was tested in 

bending to determine modulus of elasticity (MOE) and 

modulus of rupture (MOR). Lumber characteristics (knots, 

slope-of-grain, checks, etc.) and damage (nail holes, bolt 

holes, splitting, etc.) were quantified for each piece. Small 

clear bending specimens were also cut (where possible) 

from the failed lumber. These were tested according to 

ASTM standards to determine clear-wood strength. 

Results and Conclusions

The following was found from the testing and analysis of 

reclaimed Douglas-fir lumber:

The mean bending strength of full-size Douglas-fir lumber 

was found to be about 25% lower than in-grade test data of 

the same species. Mean stiffness was about 10% higher than 

in-grade test data. Existing size-effect equations are applicable for reclaimed lumber. No geographical location effect 

was found for the four locations tested. Nail holes reduced 

MOR when they were closely spaced or if they had created 

further splitting, primarily when located at the high-stress 

tension edge. In testing this reclaimed lumber, shear failures 

were found to be relatively common though the bending strength of this lumber was higher than lumber failing 

at knots. Compared with lumber that has damage as the 

grade-determining defect, the frequency of lumber failures 

involving damage were less common, suggesting that grading may be too conservative regarding damage. In addition, 

lumber failing at points of damage exhibited higher bending 

strength than lumber failing at knots. 

Results of mean bending strength of clear wood and mean 

specific gravity were essentially the same as that from historical data. Mean MOE was about 10% greater than that of 

historical data. Differences in MOR between geographical 

groups of lumber from different locations can be explained 

by differences in specific gravity. 

Recommendations

The following recommendations are made about regrading 

and reuse of salvaged lumber:

• Reclaimed lumber should be regraded before reuse. Grading rules, and possibly design guidelines, should formally 

recognize this material and provide guidance regarding 

appropriate reuse.

• Any requirements for reuse should recognize the impracticality of identifying the exact species of each piece of 

2-by lumber salvaged and accommodate some degree of 

species mixing. 

• In design, regular edge-nail holes should be placed in the 

compression zone, or away from the highest tension zone.

 i

Engineering Properties of Douglas-fir 

Lumber Reclaimed from Deconstructed 

Buildings

Robert H. Falk, Research General Engineer

Forest Products Laboratory, Madison, Wisconsin

Derek G. Maul, Structural Engineer

G Maul & Associates, Structural Engineers, Thiensville, Wisconsin

Steven M. Cramer, Professor

Department of Civil and Environmental Engineering, University of Wisconsin, Madison, Wisconsin

James Evans, Mathematical Statistician

Forest Products Laboratory, Madison, Wisconsin

Victoria Herian, Statistician

Forest Products Laboratory, Madison, Wisconsin

Background

During the last century, millions of residential homes, 

commercial and industrial buildings, bridges, and other 

structures have been built from sawn lumber and timber. 

As these structures age, lumber will become available for 

reuse (through remodeling or deconstruction). Since the turn 

of the 20th century, over 3 trillion board feet of lumber has 

been produced in the United States (Falk and others 2003). 

Much of this lumber still resides in our aging building infrastructure. Wood buildings are regularly coming out of 

service because of functional or conditional obsolescence 

or both, and demolition is typically the disposal method of 

choice. The U.S. Environmental Protection Agency estimates that the equivalent of 250,000 single-family homes 

are demolished each year in the United States (EPA 1998). 

By recovering the structural lumber alone in these buildings, 

over 1 billion board feet of usable lumber (after estimated 

recovery losses) could be reused rather than landfilled 

(Falk 2002). This volume represents about 3% of our current 

annual softwood harvest (Howard 2001).

Maximizing reclaimed lumber has positive environmental 

effects. First, more fully utilizing reclaimed lumber will reduce the volume of waste destined for landfills. Second, the 

reuse of building products reduces the volume of new building products that need to be produced and the associated 

production of greenhouse gases. Finally, the reuse of lumber 

will help conserve our natural resources and ease harvesting 

pressure on the existing forest resource.

Lumber Grading

To assure satisfactory performance in construction applications, structural lumber of a specific species is graded 

into quality classes at the saw mill. Grading agency rules 

contain grading criteria that are used to visually (or mechanically) sort lumber into quality classes. These criteria 

include specific limits on the size and location of strengthreducing characteristics such as knots, splits, checks, and 

slope-of-grain. To determine appropriate end-uses for the 

various quality grades, ASTM D 1990 engineering testing 

is performed on full-sized lumber (ASTM 2002). These test 

results are used to establish engineering design properties 

(e.g., strength, stiffness) and assure that the lumber will 

perform satisfactorily when used in a particular application. The various lumber grades are typically indicated by a 

lumber grade stamp that allows each piece to be individually 

sold and allows lumber’s widespread acceptance by engineers, architects, and building officials at the building site. 

Because existing grade criteria have been developed for 

lumber fresh from the saw mill, the current rules do not 

specifically address some characteristics commonly found 

in reclaimed lumber, such as multiple nail holes and damage from long-term use or damage from the dismantlement 

process. The damage found in reclaimed lumber takes many 

forms and is a result of original construction, a lifetime of 

use, and the dismantlement process. To what extent these 

characteristics affect lumber strength has not been quantified, and limitations in the existing grading rules can result 

in reclaimed lumber being unnecessarily downgraded or 

disallowed for reuse. 

Establishing a grade stamp specific to reclaimed lumber 

will allow each piece to be individually sold and accepted 

at building sites. Currently, lumber and timber are regularly 

salvaged from industrial buildings for use in timber-frame 

construction. For the most part, the reclaimed structural 

lumber and timber used in timber-frame construction is regraded and individual engineering designs are approved by a 

licensed engineer. Because 2-by lumber is more ubiquitous, 

it would be more practical to develop a grade stamp specific 

to reclaimed 2-by lumber so that each regraded piece can be 

individually sold.
2

Research Paper FPL–RP–650

Previous Research

Very little research has been performed on reclaimed dimensional lumber. Limited testing by Falk and others (1999c) 

suggested that reclaimed Douglas-fir lumber may have different engineering properties than today’s sawmill-produced 

lumber. Because the lumber tested in the 1999 study was a 

mixture of species and grades, group sample sizes were too 

small to make definite conclusions at other percentiles. Falk 

and others (1999b) also examined the effect of damage on 

the grade yield of lumber reclaimed from military barracks 

and found that accounting for deconstruction damage reduced lumber quality by about one grade. 

Non-destructive methods have been used to evaluate the 

elastic modulus of in-place floor joists (Lanius and others 

1981), and the clear-wood strengths of 85-year-old roof 

trusses were examined by Fridley and others (1996). Small 

clear specimens cut from truss members showed no difference in compression parallel-to-grain and flexural properties 

compared with historical data. However, these studies did 

not include destructive testing of full-size lumber to determine strength and stiffness.

Other studies have examined the mechanical properties of 

larger dimension timbers. Testing 8-in. by 8-in. columns of 

55-year-old timber revealed compressive strength and modulus of elasticity (MOE) to be greater than current National 

Design Specification for Wood-derived values (NDS 2001, 

Falk and others 2000). Another study determined that large 

heart checks reduced mean bending strength of 6-in. by 

8-in. reclaimed Douglas-fir timbers by about 15% but had 

no effect on stiffness (Green and others 2001). Rammer 

(1999) also found that splits and checks have a considerable 

effect on the residual shear strength of reclaimed timbers. 

The data reported in this paper originated, in part, from 

Maul (2004).

Selection of Lumber for Testing

This research effort involved a sampling plan designed to 

test reclaimed Douglas-fir lumber of various size, quality, 

geographical locations, and prior uses. Current methods 

to derive design properties for visual grades of commercially produced solid sawn dimension lumber are outlined 

in ASTM standard D 1990 (2000). This standard suggests 

testing two grades of lumber (separated by no more than 

one grade) and three sizes (with no more than 4 in. nominal depth between sizes). Ideally, 360 specimens should be 

tested for each size-grade cell for statistical confidence.

The three sizes of lumber tested in this study were 

2 by 6, 2 by 8, and 2 by 10. These sizes were thought to 

be the most likely sizes for reuse given their common usage in single-family home construction. Though a 2 by 4 

size is very common, we thought that it was less likely that 

this size would be reused in large-scale structural applications because of the high incidence of nail damage to these 

relatively small profile members. At the larger end, 2 by 12s 

could have been tested; however, we thought that this size is 

not as common in home construction as the three sizes chosen, and therefore chose not to test it.

ASTM D 1990 also suggests testing two grades of lumber, 

separated by one grade, so we chose Select Structural (SS) 

and No. 2. The lumber was collected from four building 

deconstruction sites and had been used as floor joists, roof 

rafters, wall members, stringers, and collar ties. Several 

thousand pieces of full-size lumber salvaged from deconstruction were graded to yield the 1,078 pieces of No. 2 and 

SS tested. Lumber that had been painted was not included in 

this study.

Locations

The collection of lumber for this project was more problematic than for most lumber studies. Because building deconstruction is not yet a universal practice throughout the United States, it was difficult finding a large quanity of lumber 

in a particular geographic area during the research project. 

For this reason, we acquired lumber from deconstruction 

projects that were active during the period of the project, 

despite these projects not being as geographically diverse as 

we originally hoped. 

Lumber could have been obtained from the deconstruction of single-family homes or from the wide array of reuse 

centers and small deconstruction projects across the country 

(Falk and Guy 2005). However, the small number of pieces 

available from any one such source would severely limit the 

statistical conclusions to be drawn from the resulting test 

data. For example, the deconstruction of a single residential 

home may only yield 50 pieces of full-size lumber available 

for grading. After grading, only a few pieces might end up 

in each cell. Because decommissioned military bases offered 

relatively large buildings that were the same age, type, and 

purpose, they were ideal targets for this study. The buildings were typically larger than a single residential home and 

yielded a greater number of lumber pieces for a given size–

grade cell. 

The lumber tested in this study was collected from deconstructed buildings at four sites: (1) barracks and warehouse, 

Fort Ord, Marina, California; (2) warehouse, Oakland Naval 

Supply Center, Oakland, California; (3) military housing, 

University of Washington Campus, Seattle; (4) warehouses, 

Twin Cities Army Ammunition Plant (TCAAP), New 

Brighton, Minnesota. All buildings were wood framed and 

had been built in the early 1940s in preparation for World 

War II. 

Fort Ord

A pilot deconstruction project of a two-story barrack 

(Fig. 1) and a light-framed warehouse at the Fort Ord Army 

base in Marina, California, yielded 2 by 8 floor joists and 

stringers and 2 by 6 roof rafters. Loading was likely very 

light, consisting of the dead load of floor and roof systems 

and coverings as well as intermittent light live load from 
 3

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

foot traffic; snow in the region is extremely rare. At Fort 

Ord, we tested 370 pieces of lumber: 

Size Grade Quantity

2 by 6 No. 2 98

 SS 12

2 by 8 No. 2 220

 SS 40

The lumber quantified is a subset of the lumber that served 

as the basis for the 1999 lumber grading study by Falk and 

others (1999b).

Oakland Naval Supply Center

Two groups of lumber were retrieved from buildings at the 

Oakland Naval Supply Center in California. These buildings, approximately 65 years old, served as warehouse and 

light manufacturing space at this World War II-constructed 

facility. Wall studs (2 by 6) as well as roof joists (2 by 10) 

were removed by deconstruction crews (Fig. 2). Roof loading was most likely limited to the dead loads of roofing material and miscellaneous hanging mechanical and electrical 

equipment, as snow is almost nonexistent in this area. The 

exterior wall studs bore the dead load of the wood-framed 

roof, wind loads, and possibly earthquake loading from 

intermittent quakes. However, no damage or overstress 

was apparent in the structure from which the lumber was 

salvaged. We tested 313 pieces of lumber from the Oakland 

Naval Supply Center: 

Size Grade Quantity

2 by 6 No. 2 16

 SS 47

2 by 10 No. 2 53

 SS 197

Twin Cities Army Ammunitions Plant

The Twin Cities Army Ammunitions Plant (TCAAP) is 

located in New Brighton, Minnesota, on a 2,383-acre site 

and originally had 255 buildings. Construction began in 

1941 and ammunitions production for World War II began 

in early 1942. Roof joists were collected for our study from 

one of the industrial wood-framed buildings (Fig. 3). The 

roofs from which the joists were collected were flat and 

subjected to heavy Minnesota snow loads, as well as dead 

loads consisting of the roofing materials and miscellaneous 

mechanical, electrical, and plumbing equipment that hung 

beneath. Only 2 by 10s were available from the TCAAP. 

The 170 pieces of 2 by 10 lumber tested includes previously 

tested lumber from Falk and others (1999c):

Size Grade Quantity

2 by 10 No. 2 53

 SS 117

 Total 170

University of Washington

The final group of lumber tested in this study came from the 

University of Washington in Seattle. Old university housing 

units, once used for the U.S. Army, were dismantled and the 

lumber collected (Fig. 4). All members were either roof rafters or floor joists. Loading was likely very light, consisting 

Figure 1—Single story Army barrack, Fort Ord, Marina, 

California.

Figure 2—2 by 6 wall studs from the Naval Supply Center warehouse, Oakland, California.
4

of the dead load of floor and roof systems and coverings as 

well as intermittent light live load. We tested 225 pieces of 

lumber at the University of Washington: 

Size Grade Quantity

2 by 6 No. 2 20 

 SS 36

2 by 8 No. 2 43

 SS 2

A total of 1,078 pieces of full size lumber were tested at all 

locations: 

Size Grade Quantity

2 by 6 No. 2 134

 SS 95

2 by 8 No. 2 387

 SS 42

2 by 10 No. 2 106

 SS 314

Total No. 2 627

 SS 451

Grand total 1,078

Grading Tested Lumber

After removal from the buildings, all lumber was evaluated 

on site, where possible, by a WCLIB grading supervisor and 

followed Standard No. 17 Grading Rules for West Coast 

Lumber (WCLIB 2000) (Fig. 5). The lumber was graded as 

Structural Joists and Planks. Basically, all lumber salvaged 

from the buildings was screened first for length. Ideally, 

pieces of the following lengths were selected for testing: 

2 by 6, 10 ft; 2 by 8, 12 ft; and 2 by 10, 14 ft. This provided 

the length necessary for end trimming (considered in grading) and resulted in a 17:1 span-to-depth ratio as required by 

testing standards (ASTM D 198 (2000)).

Some characteristics found in reclaimed lumber are not 

specifically addressed in the published grading rules. For 

example, the allowable number of nail holes in a particular 

piece is not specified. Though the grading rules do limit 

the size of a “hole” (from any cause) in the same category 

as Unsound or Loose Knots, there is no guidance on the 

equivalency of multiple nail holes and a particular size knot 

hole. Importantly, no information exists to suggest that a 

particular number of nails (concentrated or distributed) have 

the same effect on lumber failure as an unsound knot. 

In addition to the grading rule descriptions, the lumber 

grader was asked to evaluate damage from deconstruction. 

For example, splits that obviously occurred from dismantlement (indicated by the fresh break) were noted, as was end 

damage from prying members from the building. The grader 

used his best judgment about the effect of nail holes on 

Figure 3—Twin Cities Army Ammunition Plant (TCAAP) 

warehouse, New Brighton, Minnesota, before deconstruction.

Figure 4—University of Washington housing units, 

Seattle.

Figure 5—Crew grading lumber from University of 

Washington housing units, Seattle.

Research Paper FPL–RP–650
 5

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

grade. Also, mechanical gouging was equated to established 

wane requirements. An evaluation of the effects of this damage on grade yield can be found in Falk and others (1999b). 

Damage found in the end 12 in. of each board was ignored.

Species Identification

One major difference in lumber obtained directly from a 

sawmill and lumber from salvage is the assurance of species uniformity. Lumber from a sawmill typically originates 

from a single species stream as identified by the bark, needles, and geographic origin of the tree. On the other hand, 

salvaged lumber comes from a building that may contain 

a mixture of species that could be a result of the original 

building material supply chain or remodeling and repair (or 

both). Unless a grade stamp exists (which in our experience 

with this World War II-era lumber is often infrequent), species uniformity cannot be guaranteed. Also, visual identification to confirm species presented a potential problem with 

reclaimed lumber because some of the lumber was dirty or 

discolored. Though 1,078 pieces of lumber were collected 

and graded as Douglas-fir, species identification by the 

USDA Forest Products Laboratory’s Wood Identification 

Unit determined that only 980 actually belonged to this species. Table 1 indicates the other species present. Note that 

species variation only occurred in lumber salvaged from 

Fort Ord and Minnesota. Lumber from the University of 

Washington and Oakland was exclusively Douglas-fir. In 

total, over 90% of the lumber salvaged was Douglas-fir.

Moisture Content

Field measurement of lumber moisture content (MC) using 

a moisture meter was made periodically. The MC of several 

hundred pieces was measured and ranged from 8% to 14%. 

This is a very reasonable finding, as the outdoor equilibrium 

moisture content in the West and Midwest is about 12%. 

Testing Methodologies

Full Size Bending

Pretest Procedure

Upon completion of visual grading and specimen numbering 

on site, the lumber was transported to the Forest Products 

Laboratory and stored in a covered location. Most lumber 

had all nails removed before shipment from the deconstruction site; however, many required trimming to a consistent 

length. All lumber was stickered and stacked in a humiditycontrolled room for several weeks prior to testing. This 

room was maintained at 75°F and 65% relative humidity 

(12% equilibrium MC). 

Board identification numbers were logged and dimensions 

of each piece (length, width, and depth at center of span) 

were measured. Nail holes were counted over a designated 

length to calculate average spacing. We made extensive lab 

notes and included information on damage and natural defects, including location in the test span, size, and type. The 

Appendix shows a data collection sheet used for each specimen. Static modulus of elasticity (MOE), modulus of rupture (MOR), specific gravity (SG), and MC were determined 

for each full-size test specimen.

Bending Tests

Static bending tests followed ASTM D 198 (2000); however, the speed of the test was modified so failure occurred 

in approximately 1 min, rather than the 10 min specified in 

the standard.

Each board was tested in a Riehle Universal Twin Screw test 

device shown in Figure 6. Using a 10,000-lb. hydraulic actuator, each board was tested on edge in third-point bending 

Figure 6—Reclaimed 2 by 10 lumber is tested 

on a Riehle Universal Twin Screw test device 

at the Forest Products Laboratory, Madison, 

Wisconsin.

Table 1—Species of No. 2 and SS-grade lumber tested 

Location Totals 

Species Fort Ord UWa

 TCAAPb Oakland n (%)

Douglas-fir 318 226 123 313 980 91 

Larch 11 11 <1 

Hemlock 12 15 27 2 

Sugar pine 4 4 <1

White pine 3 3 <1

Western yellow pine 12 14 26 2 

Sitka spruce 15 15 1 

Western cedar 3 3 <1

White fir 1 2 3 <1

Eastern yellow pine 6 6 <1

Total 376 226 171 313 1,078 100 

a University of Washington, Seattle. b Twin Cities Army Ammunition Plant, New Brighton, Minnesota.
6

until failure. A constant displacement of 2 in. per min resulted in failures initiating in approximately 1 min. Electronic 

instrumentation included a 10-kip capacity Honeywell Sensotec load cell (Honeywell Sensing and Control, Columbus, 

OH), and a linear variable differential transducer (LVDT). 

The LVDT was attached to a yoke suspended between nails 

driven in at the neutral axis above the two reaction points. 

The LVDT stem was then attached to a nail driven in at the 

center of the board at the center of the test span. This setup 

measured the deflection of the center of the piece relative 

to the end supports. Where possible, boards were tested at 

a span-to-depth ratio of 17:1. Some boards were not long 

enough to achieve this ratio, and were tested at slightly 

lower ratios (15:1). Corrections to the data were made to 

account for these lower ratios.

During testing of the Oakland 2 by 10 lumber, a load-cell 

error was discovered that affected 49 pieces of lumber. As 

indicated in appendix C of Maul (2004), a review of the 

load-cell calibration curves and a statistical analysis of the 

data allowed the development of an error-correction factor 

so that the data could be salvaged.

Post-Test Procedure

We established a code for describing the various failure 

types (Table 2) and after each test, we assessed the type of 

failure and recorded a determination whether or not damage was involved in the failure. Failure types were grouped 

according to the mechanics of the failure (tension, compression, and horizontal end shear). The board was then sawn 

into manageable lengths and a section of the board saved for 

cutting a small clear specimen for future testing (Fig. 7). A 

moisture block was cut from the failed board shortly after 

testing to calculate MC and SG per ASTM D 4442 (2007) 

and ASTM D 2395 (2000), respectively. After determining 

MC, this moisture block was given to the FPL Wood Identification Unit for determination of species. A photograph of 

failure was also taken of every board. A 3-ft-long section of 

the board centered at the failure was cut for future strength–

ratio grading. 

Small Clear Bending

Pretest Procedure

Preparation of small clear specimens followed the secondary method of static bending in ASTM D 143 (2007). After 

cutting to the specified 1-in. by 1-in. by 16-in. size, the 

specimens were placed in a humidity-controlled room for 

several weeks to achieve approximately equilibrium MC 

(75°F, 65% RH). The specimens were carefully examined 

to assure all pieces were clear of defects. Specimens were 

rejected that contained defects such as pin knots, slope of 

grain (SOG) 1:20 and steeper, and nail holes. This adherence to the ASTM standard ensured an unbiased comparison 

to historical data. 

Static Bending Tests

All small clear specimens were tested in center-point bending at a span of 14 in. per ASTM D 143 (2000) (Fig. 8). 

Figure 7—Tested lumber marked for cutting small clear 

specimens.

Figure 8—Small clear specimens are tested in centerpoint bending.

Table 2—Failure code descriptions 

Failure

code Failure type Comments 

1 Tension (wood) Type 

2 Tension (knot) Type, size, damage involved?

3 Tension (damage) Type of damage 

4 Tension (slope of grain) Slope, damage involved? 

5 Compression Type, damage involved? 

6 Horizontal shear Type, damage involved? 

7 Invalid test Specify 

8 Other Specify 

Research Paper FPL–RP–650
 7

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

This standard specifies a displacement rate of 0.05 in. per 

min, and using this rate resulted in failures in approximately 

10 min. To make the testing timeline more reasonable, this 

rate was modified to 0.1 in. per min to achieve failure in 

approximately 5 min. All data were gathered with a similar 

electronic data acquisition system that was used with the 

full-size bending tests. A LVDT attached to an aluminum 

yoke was used to measure the deflection at the center relative to the supports. Load was measured with a 1-kip capacity Sensotec load cell. 

Post-Test Procedure

After the specimen had failed, notes were taken including 

the time until failure and type of failure. A block was then 

cut from the specimen for use in calculating SG and MC. 

Failed pieces were saved for future studies.

Test Results

Testing results are presented for both small clear specimen 

testing as well as full-size lumber tests. To analyze the data, 

a commercial statistical software package, SAS (v 8.2, SAS 

Institute Inc., Cary, NC) was used under the guidance of 

FPL statistical staff. All regression analyses were performed 

using SigmaPlot (v 7.101) (Systat Software, Inc., San Jose, 

CA).

Small Clear Results

A common assumption among wood researchers is that the 

properties of wood do not change appreciably with time, 

unless acted on by destructive or other actions that degrade 

(e.g., overloading, decay). To verify this assumption, the 

small clear data were analyzed and compared to available 

historical data on small clear wood properties. As stated earlier, these small clear specimens were cut from the full-size 

members.

Small Clear Specimens

Property Comparison to Historical Data

A total of 827 small clear specimens were tested; 26 were 

discarded from this analysis because they were species other 

than Douglas-fir or larch, and 52 were discarded because of 

an inconsistency discovered in the test setup. The properties for small clear samples (127 total pairs) taken from the 

upper and lower section of the lumber were averaged to 

maintain a sampling representative of the full-size lumber 

sample (Maul 2004). This resulted in a total of 622 pieces 

of data included in this analysis (smaller for some properties 

because of data sampling problems). Table 3 summarizes 

the calculated properties and shows a comparison to historical values. For both the reclaimed and historical data, specimens were conditioned to 12% MC; however, the historical 

data set was generated from testing 2- by 2-in. specimens. 

Obviously, this size specimen was impossible to produce 

from the reclaimed 2-by lumber tested in this study, so a 

1- by 1-in. specimen was used as allowed under ASTM 

D 245 (2000). Both data sets were tested with center-point 

bending at a span-to-depth ratio of 14:1, so a size adjustment was applied to the historical small clear MORs to allow comparison to the 1- by 1-in. reclaimed small clear data 

per ASTM D 245 (Eq. (1)). This factor was found to be 1.08 

for this case with d1 = 2 in. and d2 = 1 in.

 

(1)

where

MOR1 is modulus of rupture at d1,

MOR2 modulus of rupture at d2,

d1 member depth 1, and

d2 member depth 2

As observed in Table 3, the MORs for the reclaimed smallclear tests were only slightly lower than historical averages. 

The historical data were generated by taking the average 

of the means for Coast, Interior West, Interior South, and 

Interior North Douglas-fir from the Wood Handbook

(FPL 1999) because we don’t know the specific origin of 

the reclaimed lumber. The specific gravities were nearly the 

same with a mean difference of about 2%, which indicates 

similarity of the reclaimed resource to the historical data. 

1/ 9

2

1

2 1 













 = d

d MOR MOR

Table 3—Reclaimed and historical small clear data for 

Douglas-fir 

Reclaimed 

Property No. Mean COVa Historical

meanb, c

Difference

mean (%)d

MOR (×103 lb/in2) 622 13.59 16.3 13.7e 0.7 

MOE (×106 lb/in2) 622 2.06 18.4 1.86 10.8 

Specific gravity (12% MC) 582 0.48 11.1 0.49 2.0 

Moisture content (%) 586 11.4 8.9 12.0 5.0 

a

 Coefficient of variation is standard deviation/mean. b Average of Coast, Interior West, and Interior North regions. 

c

Percentage difference is (historical average – reclaimed average) / historical 

 average. 

d As reported in the Wood Handbook (FPL 1999). e Historical MOR adjusted from 2 in. depth to 1 in. (see Eq. (1)). 

MOR2 = MOR1
8

Only the MOEs differ and reclaimed small-clear stiffness is 

greater than historical averages by approximately 11%. This 

is also depicted in Figure 9 as a plot of MOE compared with 

MOR. Note that only summary statistics were available for 

the historical data, so a comparison was only possible at the 

means. 

Property Relationships

Specific gravity is known to be a predictor of bending MOE, 

which is a general predictor of MOR. Research has shown 

that within a species, these properties can be modeled using a linear function (FPL 1999). These relationships are 

illustrated for the reclaimed small clear data in Figures 10 to 

12. Linear regression lines for SG compared with MOR, SG 

compared with MOE, and MOE compared with MOR are 

also shown. Specific gravity data shown are at 12% MC.

As indicated in Figures 10 and 11, SG is a better predictor 

of MOR than of MOE. However, MOE is a better predictor 

of MOR (Fig. 12) than is SG (Fig. 10).

Location Comparison

The clear wood properties of the lumber salvaged from different locations were also evaluated. Statistical analyses 

were performed in which simultaneous comparisons of the 

groups were made for three properties: MOR, MOE, and 

SG. All species were included in this comparison. Both sizes 

of lumber collected from Oakland (2 by 6 and 2 by 10) 

exhibited higher MOR values than the 2 by 6 Fort Ord and 

2 by 8 Washington groups, based on 95% or higher confidence (Table 4). Similar trends are shown for both MOE 

(Table 5) and SG (Table 6). The SG for the 2 by 6 Fort Ord 

lumber is lower than every other group except the 2 by 8 

lumber from Washington (Table 6). 

The correlation between these three properties can be illustrated by ranking the means, for each size-location, for 

each property. Based on this observation, it is reasonable to 

assume that the difference in MOR is a result of the effect 

of SG. To investigate this assumption, information from the 

linear regression analysis was used to adjust MOR for SG. 

Recall the relationship for MOR as a function of SG 

(Eq. (2)). The slope in this equation provides an estimate for 

change in MOR for a given change in SG (Eq. (3)). Using 

the known values for MOR and SG, a predicted value for 

MOR may be determined for a given reference SG 

(Eq. (4)). The reference SG was set at the overall average 

(0.48), and the group comparisons were made, as before, for 

MOR (Table 7). 

 MOR = 28.1 SG – 0.65 (2)

 

(3)

(4)

(MORpredicted – MOR)

(SGreference – SG) = 28.1

∆MOR

∆SG = 28.1

Research Paper FPL–RP–650

Figure 9—Comparison of reclaimed small clear data to historical averages of modulus of elasticity 

(MOE) and modulus of rupture (MOR). 
 9

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

Figure 10—Small clear linear regression relationships for modulus of rupture (MOR) as a function of 

specific gravity.

Figure 11—Small clear linear regression relationships for modulus of elasticity (MOE) as a function 

of specific gravity.
10

The result of this analysis of covariance indicates that MOR 

values do not vary significantly as a result of location and 

differences in SG can account for differences in MORs for 

the small clear specimens. Overall, the SGs for the Oakland 

groups were higher than average, whereas the Minnesota, 

2 by 6 Washington, and 2 by 8 Fort Ord groups were 

average, and the 2 by 6 Fort Ord and 2 by 8 Washington 

groups were below average.

Full-Size Lumber

Knowing that the small clear data exhibit properties comparable with historical values, the next step is to examine 

data from the full-size bending tests. The first data to be presented are a statistical summary of 991 pieces of Douglas-fir 

and larch (Table 1) for the three sizes and two visual grades 

tested. Examination of these data will determine if the size 

equations developed for new lumber apply to reclaimed 

lumber. If so, the data can be adjusted to a single size and 

0.5 1.0 1.5 2.0 2.5 3.0 3.5

4

6

8

10

12

14

16

18

20

22

MOR (×103 lb/in2

)

MOE (×106 lb/in2)

MOR = 4.41 × MOE + 4.49 (r2 = 0.56)

Figure 12—Small clear linear regression relationship for modulus of rupture (MOR) as a function of 

modulus of elasticity (MOE).

Table 4—Small clear modulus of rupture (MOR) 

group comparisons 

 MOR (×103

/in2)

Size Location Mean COVa No. Groupingb

2 by 10 Oakland 14.21 15.6 307 A 

2 by 6 Oakland 14.16 13.8 54 A 

2 by 6 Washington 13.78 15.0 53 A, B 

2 by 8 Fort Ord 13.49 21.9 59 A, B 

2 by 10 Minnesota 13.17 15.7 116 A, B 

2 by 8 Fort Ord 12.91 16.6 32 B 

2 by 6 Washington 12.77 15.9 128 B 

a

 Coefficient of variation. 

b Tukey grouping. Means with the same letter are not significantly 

 different (95% confidence). 

Table 5—Small clear modulus of elasticity (MOE) group 

comparisons 

MOE (×106 lb/in2

)

Size Location Mean COVa

 No. Groupingb

2 by 10 Oakland 2.21 15.9 307 A 

2 by 6 Oakland 2.12 16.3 54 A, B 

2 by 6 Washington 2.08 21.5 53 A, B 

2 by 10 Minnesota 2.03 16.2 116 A, B, C 

2 by 8 Washington 1.96 18.7 128 B, C, D 

2 by 8 Fort Ord 1.88 23.5 59 C, D 

2 by 6 Fort Ord 1.79 16.5 32 D 

a

Coefficient of variation. 

b Tukey grouping. Means with the same letter are not significantly different 

 (95% confidence). 

Research Paper FPL–RP–650
11

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

combined for broader analyses. Also, the effect of including other species into these data will be examined. Values 

of interest included the number of samples used in the calculation, the sample mean, the 5th percentile estimate (at a 

75% lower confidence level) and the coefficient of variation 

(Tables 8 and 9). 

Property Comparisons

Tables 8 and 9 tabulate the various properties for the different size-grade lumber groups. Figures 13 and 14 provide a 

visual measure of the effect of member size, grade, and the 

effect of SG and MOE on MOR. The graphs are twovariable scatter plots for each size-grade of tested lumber 

and include bi-directional 95% confidence interval bars. 

A grade effect on MOE for all sizes is revealed in Figure 13 

and indicates that within a grade, the MOEs are statistically 

the same for the 2 by 6 and 2 by 10 sizes. However, the 

2 by 8 size is lower for the SS grade and tends to be lower, 

though not statistically different, than the No. 2 grade. The 

lower SG for the 2 by 8 Washington group drives down the 

stiffness within each grade of the overall 2 by 8 group and 

causes a slightly lower MOR for the SS grade (Fig. 14). The 

previous distributions show that the higher grade 2 by 6 and 

2 by 10 groups had slightly larger SGs, a result of a larger 

number of Oakland pieces within those groups. 

Distributions

As expected, the distributions of MOR for each size-grade 

exhibit non-normal distribution characteristics (Fig. 15). 

Size effect is illustrated by the shift in curves. 

The SG distributions exhibit relatively normal characteristics (Fig. 16). The distributions for all the No. 2 sizes and 

the 2 by 8 SS groups appear to be the same shape. The 

2 by 6 and 2 by 10 SS groups are shifted to the right, 

Table 6—Small clear specific gravity (SG) group 

comparisons 

 SG (12%) 

Size Location Mean COVa No. Groupingb

2 by 10 Oakland 0.492 10.0 290 A 

2 by 6 Oakland 0.491 10.1 43 A 

2 by 8 Fort Ord 0.488 13.5 56 A 

2 by 10 Minnesota 0.485 11.5 106 A 

2 by 6 Washington 0.480 8.8 53 A, B 

2 by 8 Washington 0.456 11.0 128 B, C 

2 by 6 Fort Ord 0.445 13.0 32 C 

a

Coefficient of variation. 

b Tukey grouping. Means with the same letter are not significantly 

 different (95% confidence). 

Table 7—Small clear modulus of rupture (MOR) group 

comparisons adjusted by specific gravity 

MOR (×103 lb/in2

)

Size Location Mean COVa No. Groupingb

2 by 6 Fort Ord 13.88 18.3 32 A 

2 by 10 Oakland 13.86 11.4 290 A 

2 by 6 Washington 13.78 10.1 53 A 

2 by 6 Oakland 13.75 9.88 43 A 

2 by 8 Washington 13.44 9.3 128 A 

2 by 8 Fort Ord 13.37 13.9 56 A 

2 by 10 Minnesota 13.1 12.8 106 A 

aCoefficient of variation. 

b Tukey grouping. Means with the same letter are not significantly different 

 (95% confidence).

Table 9—Statistical summary for reclaimed Select Structural (SS) lumber, Douglas-fir and larch 

 2 by 6 2 by 8 2 by 10 

Property (units) No. 2 Mean 5th% COVa No. 2 Mean 5th% COV No. 2 Mean 5th% COV 

MOR (×103 lb/in2) 96 7.03 3.53 31.5 163 6.11 2.96 37.1 291 5.65 2.82 31.8 

MOE (×106 lb/in2) 94 2.13 1.46 18.3 125 1.90 1.35 18.2 254 2.19 1.57 17.5 

Specific gravity 96 0.52 0.42 10.9 163 0.49 0.40 13.2 291 0.51 0.42 10.8 

Moisture content (%) 96 11.8 10.3 8.5 163 13.2 11.6 5.7 291 10.4 8.6 9.9 

a

Coefficient of variation. 

Table 8—Statistical summary for reclaimed No. 2 lumber, Douglas-fir and larch 

2 by 6 2 by 8 2 by 10 

Property (units) No. Mean 5th% COVa No. Mean 5th% COV No. Mean 5th% COV

MOR (×103 lb/in2) 107 5.28 2.30 41.7 241 4.79 2.08 43.4 93 4.04 1.68 42.4 

MOE (×106 lb/in2) 103 1.79 1.16 23.3 43 1.69 1.07 18.8 78 1.78 1.12 21.9 

Specific gravity 107 0.50 0.41 11.3 241 0.48 0.40 10.7 93 0.49 0.40 12.9 

Moisture content (%) 107 12.3 10.3 7.6 241 11.7 9.7 10.1 93 11.4 8.5 11.5 

 a Coefficient of variation. 
12

suggesting greater SG values. This can be explained because 

a larger percentage of the data within these two SS groups 

came from Oakland, where SGs were found to be higher 

(Table 6). Modulus of elasticity distributions show the 

same trend as for SG and for the same reason (Fig. 17). 

Size Effect

Lumber testing has historically shown that as depth of a 

bending member increases, MOR decreases (Bohannan 

1966). This size effect for the reclaimed lumber tested is 

shown in Figure 18. A multiple comparison test was performed and indicated that for the No. 2 grade, average 

2 by 8 MOR is statistically different than the 2 by 10 MOR, 

but not for the 2 by 6 MOR. The reverse is indicated for the 

SS grade, where the average 2 by 8 MOR is statistically 

different than the 2 by 6 MOR, but not different than the 

2 by 10 MOR. 

Linear regressions were determined for each grade relating 

mean MOR values to the actual member depth (Table 10, 

Fig. 19). This was done to compare the size relationship for 

MOR means and the 5th percentile estimate at the lower 

75% confidence level. The 5th percentile estimate values 

are important, as ASTM D 1990 specifies this is the typical 

statistical value used to develop design properties (ASTM 

2000). As indicated in Figure 19, the linear fits for each 

grade are nearly parallel at both the mean and 5th percentile 

levels.

The overall consistency of MOR compared with size model 

of both size and grade suggests that no major irregularities 

exist in the overall data set. Despite the disproportioning of 

sources within some of the size-grade cells, the MOR values 

are not appreciably affected in this overall model.

More common size models take on the form of a power 

relationship (equation (5.1), ASTM D 245). The size relationship for MOR from ASTM D 1990 takes on a slightly 

different form (Eq. (5)). This model will be compared to a 

nonlinear regression for the reclaimed lumber data of the 

same form. Note that the testing was performed at a spanto-depth ratio of 17:1 (Eqs. (6) and (7)). Plugging Eq. (6) 

and Eq. (7) into Eq. (5) and reducing and combining terms 

gives Eq. (8). This equation can be expanded into Eq. (9) 

and collecting terms written as Eq. (10). The resulting constant C (Eq. (11)) is a reference point calculated from the 

reclaimed MOR and depth means given in Tables 8 and 9 

for each grade. Table 11 indicates the calculation of C using a weighted average to combine sizes. The constant is 

very consistent between different sizes within the SS grade, 

whereas the 2 by 8 value is higher than the 2 by 6 and 

2 by 10 within the No. 2 grade.

 (5)

0

2

1

0.14

2

1

0.29

2

1

2 1 













































 = T

T

L

L

d

d MOR MOR

Figure 13—Modulus of elasticity (MOE) compared with modulus of rupture (MOR) plot of averages by size and grade. CI is confidence interval.

Research Paper FPL–RP–650

MOR2 = MOR1

0.29 0.14 0
13

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

Figure 14—Specific gravity (SG) compared with modulus of rupture (MOR) plot of averages by 

size and grade. CI is confidence interval.

Figure 15—Modulus of rupture (MOR) cumulative distributions by size and grade.
14

Figure 16—Specific gravity (SG) cumulative distributions by size and grade.

Figure 17—Modulus of elasticity (MOE) cumulative distributions by size and grade.

Research Paper FPL–RP–650
15

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

Figure 18—Size effect on modulus of rupture (MOR) for No. 2 and SS grades. CI is confidence interval.

Figure 19—Size effect model for mean and 5th percentile characteristic modulus of rupture (MOR) 

values for No. 2 and SS grades.
16

where

MOR1 is modulus of rupture at volume 1,

MOR2 modulus of rupture at volume 2,

d1 depth at MOR1,

d2 depth at MOR2,

L1 length at MOR1, 

L2 length at MOR2,

T1 thickness at MOR1, and

T2 thickness at MOR2

 L1 = 17 d1 (6)

 L2 = 17 d2 (7)

(8)

(9)

(10)

(11)

Nonlinear regression curves were then fitted to the No. 2 

and SS data groups and plotted in conjunction with the derived ASTM D 1990 (Eq. (10)). As shown in Figure 20, the 

curves for the reclaimed lumber data match the ASTM equations quite well. This indicates that the size-effect 

equations established for new lumber are applicable to reclaimed Douglas-fir lumber.

Comparison to Other Data

As was done with the small clear data, it is logical to compare the full-size reclaimed lumber data to existing mill 

lumber data sets. As explained earlier, the major difference 

between the lumber resource produced in a sawmill and the 

reclaimed lumber resource is the presence of damage in the 

reclaimed lumber. Ideally, we would like to quantify the effects of this damage on lumber properties. From a research 

standpoint, the ideal way to do this would have been to 

set aside, at the time of construction (in this case, 1942), a 

grade- and MOE-matched sample of lumber for future testing. Unaffected by the many years of service life as well as 

the damage imposed by construction and deconstruction, 

this sample would serve as a control to the lumber tested in 

this study and provide a means to quantify the damage variable. Unfortunately, no such sample exists. So, the best we 

can do is to compare the reclaimed lumber data to existing 

lumber data. The in-grade program (Green and Evans 1988) 

provides the most logical data set for this comparison. 

In-Grade Comparison

Table 12 shows the SG data collected during the in-grade 

program (Green and Evans 1989). Specific gravity information was not available for all of the sizes and grades of 

interest here. In fact, of the six size–grade combinations, SG 

information only exists for one. The average SG for all sizes 

and grades of reclaimed Douglas-fir tested in this study was 

0.498, which is very close to the in-grade average of 0.494. 

0.43

2

1

2 1 













 = d

d MOR MOR

From this standpoint, the reclaimed lumber resource appears 

to be very similar to the wood resource tested between 1977 

and 1987 (Green and Evans 1989). The next step is to see 

how strength and stiffness compare.

All in-grade lumber was tested in third-point bending at a 

span-to-depth ratio of 17:1; however, deflections were measured at the load points. For the reclaimed data, deflections 

were measured at the center point of the member relative to 

the supports. A correction factor of 0.993, based on ASTM 

D 2915 and ASTM D 2915-03 (2000) was used to correct 

the difference between the two data sets; however, the 

effect on summary statistics was insignificant. Because the 

in-grade lumber was field tested, MC and temperature could 

not be controlled. However, these data were recorded, and 

adjustments (ASTM D 1990) were made to a reference MC 

of 12% and a temperature of 75°F, the same as the test conditions for the reclaimed lumber. The MOE and MOR are 

reported to reflect those conditions (Green and Evans 1988) 

Table 13 compares the mean MOR and MOE values for 

the reclaimed data to the in-grade data for the sizes and 

grades of interest. Note that Table 13 does not contain a 

comparison for the 2 by 6 data, as 2 by 6s were not tested 

within the in-grade program. Average MCs and specific 

gravities were very similar to in-grade values for the individual size-grade groups.

The trends in MOE and MOR are quite interesting. The 

percentage difference column of Table 13 shows that MOR 

is roughly 26% lower for the reclaimed lumber. The higher 

grades also show a greater difference than the lower grades. 

The question is why the bending strength is lower. Based on 

the small clear results, it is not likely that the wood experienced some degradation on the microscopic level from load 

duration, temperature, or moisture exposure. Has damage 

from drying, nail holes, or the deconstruction process on the 

macroscopic level reduced bending strength? 

Conversely, opposite trends exist for MOE. For all but one 

of the size-grade groups (and that group is only 43 pieces), 

the reclaimed lumber MOEs are higher by approximately 

9% overall. This is consistent with what was seen in the 

small clear data (Table 3). 

In summary, based on the comparison to the in-grade data, 

the reclaimed lumber resource is very similar for SG. Despite this, MOR is approximately 26% lower and stiffness 

is greater by about 9%. 

Table 10—Modulus of rupture (MOR) as a function of size 

linear regression relationships based on means and 5th 

percentile estimate values 

MOR value (×103 lb/in2) Grade

A1

((×103 lb/in2

)/in) 

A0

(×103 lb/in2

)

Mean No. 2 – 0.34 7.15 

SS – 0.38 9.00 

5th percentile No. 2 – 0.17 3.25 

SS – 0.20 4.52 

MOR2 = MOR1

0.43

MOR2 = MOR1 (d1)0.43 (d2)–0.43

MOR2 = C(d2)–0.43

C = MOR1(d1)0.43

Research Paper FPL–RP–650
17

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

Analysis of Full-Size Lumber 

by Size and Grade

Location and Member Type

In this section, data from testing full-size lumber will be reviewed, with a specific look at the effects of location, member type, and damage on bending strength and stiffness. 

Based on previous analysis, it was apparent that lumber size 

and grade have a significant effect on MOR. For this reason, 

the data were sorted into size-grade-location groups and 

pair-wise comparisons of the properties of MOR, MOE, and 

MC were made using a Tukey test at 95% confidence that 

the means are not equal. Graphs were also produced comparing average properties of MOR, MOE, and SG for the SS 

and No. 2 grades (Tables 14–16 and Figs. 21–26). 

Table 11—Calculation of constant C for size model, Eq. (11) 

Grade Nominal size N

MOR

(×103 lb/in2

) Depth (in.) 

MOR (d)

0.43

(×103

 lb/in) 

6 107 5.28 5.46 10.95 

8 241 4.79 7.33 11.27 

10 93 4.04 9.15 10.46 

No. 2 

Weighted average = 11.02 

6 96 7.03 5.42 14.53 

8 163 6.11 7.31 14.37 

10 291 5.65 9.09 14.60 

SS

Weighted average = 14.52 

Table 12—In-grade Douglas-fir specific gravity 

information

Size Gradea No. Mean SGb

SS 817 0.51 

No. 2 767 0.49 

No. 1 381 0.48 

Construction 275 0.48 

Standard 273 0.48 

Utility 273 0.47 

2 by 4 

Stud 227 0.49 

2 by 8 No. 2 972 0.50 

All All 3985 0.49 

aBased on West Coast Lumber Inspection Bureau grading rules 

 Standard 17. 

b SG is specific gravity. The mean is based on oven-dry weight 

 and volume. 

Table 13—Comparison of in-grade and reclaimed data for full size lumber, Douglas-fir only 

Reclaimed In-gradeb

Percentage 

differencec

Size Gradea Property (units) N Mean 5th%d

 COVe N Mean 5th% COV Mean 5th% 

MOR (×103 lb/in2) 241 4.79 2.08 43 1964 6.25 2.47 42.7 23.4 15.9 

MOE (×106 lb/in2) 43 1.68 1.07 19 1964 1.62 1.02 25.1 – 4.1 – 4.5 

Moisture content (%) 241 11.7 9.7 10 

No. 2 

Specific gravity 241 0.48 0.40 11 

MOR (×103 lb/in2

) 163 6.11 2.96 37 493 8.48 4.09 30.4 28.0 27.6 

MOE (×106 lb/in2

) 125 1.90 1.35 18 493 1.91 1.31 20.7 0.4 –3.9 

Moisture content (%) 163 13.2 11.6 6 

2 by 8 

SS

Specific gravity 163 0.49 0.40 13 

MOR (×103 lb/in2

) 93 4.04 1.68 42 388 5.45 2.16 46.3 25.9 22.1 

MOE (×106 lb/in2

) 78 1.78 1.12 22 388 1.59 1.02 24.7 – 12.2 – 9.5 

Moisture content (%) 93 11.4 8.6 11 

No. 2 

Specific gravity 93 0.49 0.40 13 

MOR (×103 lb/in2

) 291 5.65 2.82 32 414 7.84 3.83 29.8 27.9 26.2 

MOE (×106 lb/in2

) 254 2.19 1.57 18 414 1.92 1.31 20.0 – 13.9 – 19.5 

Moisture content (%) 291 10.4 8.6 10 

2 by 10 

SS

Specific gravity 291 0.51 0.42 11 

aBased on West Coast Lumber Inspection Bureau grading rules Standard 17. 

b Data adjusted to 12% MC, 75° F, and tested at 17:1. 

c (in-grade – reclaimed) / (in-grade). 

d 5th percentile nonparametric estimate. 

eCoefficient of variation. 
18

We observed the following:

• For the 2 by 6 SS grade, no statistical difference was detected at 95% confidence between the MOR for Fort Ord 

and that for Washington, despite the large difference between values (Table 14).

• For the 2 by 8s, MOR was statistically the same for the 

No. 2 grade, but the SS grade Fort Ord boards had greater 

average MOR than Washington (7.55 × 103 lb/in2

compared with 6.69 × 103 lb/in2) (Table 15). This is likely 

explained by different average SGs, 0.53 compared with 

0.48.

• For the 2 by 10 SS grade, Oakland exhibited greater MOR 

than Minnesota, likely explained by an effect of SG 

(Table 16).

• A statistical non-significance test showed that all three 

sites are similar in any pair-wise combination of MOR.

• The sample sizes for 2 by 6 SS from Fort Ord and No. 2 

from Oakland and Washington are probably too small for 

meaningful conclusions. 

Research Paper FPL–RP–650

Figure 20—Nonlinear regression size model comparison to derived ASTM D1990 equation for No. 2 and SS grades 

(Douglas-fir).
19

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

Table 14—2 by 6 location comparisons 

Fort Ord (F) Oakland (O) Washington (W) 

Grade Property (units) Mean COVa

 (%) No. Mean COV (%) No. Mean COV (%) No. Different pairsb

MOR (×103 lb/in2) 5.51 41.7 71 4.79 49.2 16 4.85 33.9 20 

MOE (×106 lb/in2) 1.74 23.2 71 1.96 22.8 16 1.82 23.2 16 

Moisture content (%) 12.7 4.8 71 11.7 11.1 16 11.6 8.7 20 F & O, F & W

No. 2 

Specific gravity 0.48 10.2 71 0.52 11.1 16 0.52 12.2 20 NAb, c

MOR (×103 lb/in2) 7.95 30.1 12 7.27 30.8 47 6.42 31.2 37 

MOE (×106 lb/in2) 2.13 21.6 12 2.21 17.1 47 2.03 18.1 35 

Moisture content (%) 12.4 2.9 12 11.6 9.1 47 11.8 8.5 37 F & O 

SS

Specific gravity 0.50 12.0 12 0.53 10.8 47 0.51 10.0 37 NAc

aCoefficient of variation. 

b Tukey's studentized range (HSD) test at 95% or better confidence (SAS v8.2). NA is not applicable. c Data summary provided for specific gravity (SG); however, a statistical comparison was not performed since SG is not well correlated to

 grade. 

Table 15—2 by 8 location comparisons 

Fort Ord Washington 

Grade Property (units) Mean COVa

 (%) No. Mean COV (%) No. Different pairsb, d

 MOR (×103 lb/in2) 4.87 44.1 198 4.41 38.6 43 N 

 MOE (×106 lb/in2) — — 0 1.69 18.8 43 

 Moisture content (%) 11.5 9.6 198 12.8 6.8 43 N 

No. 2 

 Specific gravity 0.48 11.0 198 0.48 9.6 43 NA 

 MOR (×103 lb/in2

) 7.55 30.0 37 5.69 36.9 126 Y 

 MOE (×106 lb/in2) — — 0 1.90 18.2 125 

 Moisture content (%) 13.0 5.1 37 13.2 5.8 126 N 

SS

 Specific gravity 0.53 12.8 37 0.48 12.5 126 NAc

a

 Coefficient of variation. 

b Tukey's studentized range (HSD) test at 95% or better confidence (SAS v8.2). c NA, data summary provided for specific gravity (SG); however, a statistical comparison was not performed because SG is not well 

 correlated to grade. N, the pairs are not statistically different; Y, a statistical comparison indicates that the pairs are different. d

 MOE data not available for 2 × 8 Fort Ord due to error in data collection hardware. 

Table 16—2 by 10 location comparisons 

Oakland Minnesota 

Grade Property (units) Mean COVa

 (%) No. Mean COV (%) No. Different pairsb

 MOR (×103 lb/in2) 4.07 43.1 53 3.99 41.8 40 N 

 MOE (×106 lb/in2) 1.84 21.1 53 1.66 22.3 25 N 

 Moisture content (%) 12.0 5.8 53 10.5 13.8 40 Y 

No. 2 

 Specific gravity 0.51 11.5 53 0.47 13.7 40 NAb

 MOR (×103 lb/in2

) 5.84 29.6 197 5.26 35.8 94 Y 

 MOE (×106 lb/in2

) 2.25 17.1 197 1.99 15.0 57 Y 

 Moisture content (%) 10.5 7.1 197 10.1 14.1 94 Y 

SS

 Specific gravity 0.53 9.8 197 0.49 11.4 94 NAc

aCoefficient of variation. 

b

 Tukey's studentized range (HSD) Test at 95% or better confidence (SAS v8.2). c NA, data summary provided for specific gravity (SG); however, a statistical comparison was not 

 performed because SG is not well correlated to grade. N, the pairs are not statistically different; Y, a 

 statistical comparison indicates that the pairs are different. 
20

Figure 21—Modulus of Rupture (MOR) comparison by location for SS Grade. CI is confidence interval.

Figure 22—Modulus of elasticity (MOE) comparison by location for SS Grade.

Research Paper FPL–RP–650
21

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

Figure 23—Specific gravity (SG) comparison by location (SS Grade).

Figure 24—Modulus of rupture (MOR) comparison by location (No. 2 Grade). CI is confidence 

interval.
22

Figure 25—Modulus of elasticity (MOE) comparison by location for No. 2 Grade.

Figure 26—Specific gravity (SG) comparison by location for No. 2 Grade.

Research Paper FPL–RP–650
23

Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

For the samples of lumber obtained in this study, member 

uses (for example, floor joist, roof joist, stud) are for the 

most part unique to each size-location group; thus, separate 

analyses for member use are moot. For example, all of the 

2 by 6s from Oakland were wall studs. All of the 2 by 10s 

from Oakland and most of the 2 by 10s from Minnesota 

were roof joists; a few (12 of 125) of the Minnesota 

2 by 10s were stringers. All the 2 by 6s from Fort Ord 

and most of the 2 by 6s from Washington were rafters; a 

few (6 of 57) of the Washington 2 by 6s were rafter ties or 

tension chords. These two groups with a slight portion of 

different member types did not contain enough samples to 

overcome variability and detect an effect of member use. 

Lumber Damage

To better understand how and to what extent damage influences strength, it was necessary to categorize it. Three 

damage categories were developed and were based on the 

characteristics observed in the lumber before and after testing. These categories include (1) nail holes, (2) splitting, 

and (3) other mechanical damage. Specific codes to indicate 

each type are shown in Table 17 and were used to describe 

damage involved in board failures. Nail-hole damage was 

further defined by the geometry of the hole relative to the 

board face and edge. Splitting damage was further defined 

based on how the split was created (e.g., holes causing stress 

concentrations at a grain line or drying/seasoning). The last 

category, other mechanical damage, describes other ways 

the cross section of the board may have been damaged, 

including wane-like gouging, drilled holes, and cuts 

or notches (Fig. 27). 

Nail Holes

Nail holes are almost always present in reclaimed lumber 

and can be found on every board face, including the ends. 

Face-nail holes (those nails found on the wide face of the 

lumber) are typically caused by nailing of bridging or hardware. Edge-nail holes are commonly found on joists along 

an entire edge of a board. Usually these nails are found 

along one of the two board edges and resulted from the 

prior attachment of a cladding surface (i.e., roof, wall, or 

floor). Depending on the thickness of the cladding surface, 

an 8d, 10d, or 12d nail was typically used. Analogous to an 

edge knot, edge-nail holes can potentially reduce bending 

strength of a bending member if the edge of the board containing the nail holes is loaded in tension. Because edge-nail 

holes have potentially more impact on bending strength than 

nail holes on other board faces, a considerable amount of 

analysis was performed to quantify their effect.

Edge-Nail Holes

To determine if edge-nail holes had an effect on board properties, the orientation of the edge-nail holes to testing orientation was tracked. Basically, boards with edge nails present 

were oriented in the test machine with the nail edge up (nail 

holes in compression zone) or nail edge down (nail holes in 

tension zone). Boards were ranked by dynamic MOE (transverse vibration) and then pairs with adjacent MOEs were 

assigned to alternate orientations (nail holes up or down). In 

addition, the nails were counted over the center third of the 

test span to determine the average number of holes per foot. 

Edge-Nail Spacing

Some grading rules, such as WCLIB Standard No. 17, contain provisions for grading larger holes as well as smaller 

holes (WCLIB 2000). Depending on board size and grade, 

the grading rule allows a maximum size (average diameter) 

loose knot or hole for a particular grade. As a footnote, the 

grading rules allow “one hole or equivalent holes per __ ft”, 

with the allowed length dependent on grade. Also stated is 

that holes shall be measured the same as knots, unless noted 

otherwise. These rules for allowed hole sizes are based on 

engineering mechanics and reduction in section modulus. 

The grading rules do not contain specific guidelines for the 

measurement of edge-nail holes. The grade rules state that 

holes that extend only partially through a piece may also 

be designated as surface pits (see definition section 716 of 

grade rules). Further, nail holes would be defined as either 

a pin hole (if less than 1/16 in. diameter) or medium (small) 

hole if less than 1⁄4 in. diameter. One could also draw a parallel to the measurement of a spike knot located along the 

Table 17—Damage codes 

General category Code Description 

NE Edge-nail holes (into 1-1/2-in. edge) 

NF Face-nail holes (through board wide face) 

Nail hole 

damage

NT Toenail holes (diagonal from face to edge) 

SD Through splits from drying 

SN Through splits from nail holes 

Through splitting 

damage

SH Through splits from manmade larger holes 

G Mechanical gouging 

H Manmade drilled holes 

Other mechanical 

damage

CN Cuts and notches 
24

board edge, which does not appear on the three other 

board faces. This particular knot is defined as having a 

displacement equal to half its diameter (WCLIB 2000). 

So long as the nail does not penetrate more than half the 

depth of the board, measuring the displacement of the nail 

hole as half the diameter of the hole is conservative. This 

would seem a valid assumption, as typical nail-embed 

depths do not exceed 2-5/8 in., which is half the depth of a 

2 by 6 and less than the length of a 10d nail (3 in. minus a 

typical sheathing thickness (3/4 in.)). We will refer to this 

assumption about edge-nail hole measurement as the "spikeknot analogy.”

We used the spike-knot analogy to calculate an equivalent 

number of holes1 per foot allowed for the two grades and 

three lumber sizes evaluated in this study. Two hole diameters, 1/8 in. and 3/16 in., were assumed in the analysis and 

represent hole sizes that might be expected in reclaimed 

lumber (Table 18). 

Also in the far right column of Table 18 is the average nail 

hole spacing measured for the different lumber size-grade 

groups. Cumulative distributions of these measurements 

are shown in Figure 28. The edge-nail holes were typically 

around 1/8 in. in diameter2, and sometimes a bit larger if 

the nails were pried laterally during removal. One particular 

group, Washington 2 by 6s, had noticeably smaller edge-nail 

holes3. In reality, there is some damage around nail holes 

from stressing, water intrusion, drying, and iron sickness 

that has an effect on the effective size of the hole. This is 

1 By definition, equivalent holes per foot does not pertain to equivalent hole 

 area, but rather equivalent diameters, as knots and holes are measured by 

 the amount of board cross section that is displaced. 

2 Nails retrieved from the Washington 2 by 8s measured 1/8 in. by 3 in. 

 long, comparable to a 10d box nail.

3 Nails retrieved from the Washington 2 by 6s were non-standard and 

 measured 3/32 in. by 1-1/8 in. long, similar in diameter to a 6d box nail, 

 but the length of a 3d box nail.

difficult to universally quantify; however, based on our visual assessment of hundreds of boards, 3/16 in. would seem 

a reasonable upper limit.

A comparison of the measured edge-nail hole frequencies 

with the allowable number of nail holes by the spike-knot 

analogy described above indicated that the 2 by 8 SS group 

satisfies the criteria, whereas the 2 by 6 SS group satisfies 

the nominal 1/8 in. diameter but not the upper limit 

3/16 in. diameter. The 2 by 8 SS group satisfies the requirement; however, the 2 by 10 SS group exceeds the criteria 

(5.8 holes compared with a limit of 5.0 holes by the 1/8-in. 

diameter hole limitation). The 2 by 10 SS group would have 

met the requirements of a No. 1 grade, however (Table 18). 

All the No. 2 boards meet the spike-knot analogy 

requirements.

For two of these groups of lumber (2 by 8s from Washington and 2 by 10s from Oakland), the grader made a blanket 

statement that the SS grade boards with edge-nail holes 

should probably be downgraded to No. 2. It was the grader’s 

opinion that the edge-nail holes over a specific length of 

board could be added up to determine an equivalent knot 

size and that knot size would determine grade. Though 

grading is not an exact science and is based on experience, it 

appears that the grader was correct in suggesting the downgrade; however, the above analysis suggests that a downgrade to No. 1 is a sufficient reduction for edge-nail holes. 

Next, we will look at the effect of these edge-nail holes on 

bending strength to see if the same conclusion can be drawn.

Edge-Nail Orientation

The effect of edge-nail hole orientation (edge nails up or 

down in bending test) on strength and stiffness was also

assessed. This analysis includes both data from this study 

as well as data from an earlier reclaimed lumber study 

Figure 27—Examples of “other mechanical damage."

Research Paper FPL–RP–650
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

25

(Falk and others 1999c). In the earlier study, only edge-nail 

hole orientation was tracked, not specific nail-hole spacing. 

Table 19 shows a statistical summary, including means and 

coefficient of variation for MOR. Also included are differences for the up (nail holes on the compression edge) 

and down (nail holes on the tension edge) means as well 

a simultaneous comparison of group MOR means at 95% 

confidence. Different MOR pairs are reported in the far right 

column.

In general, edge-nail holes on the tension side result in a 

lower board bending strength than when on the compression 

side. There was one exception to this, the 2 by 6 SS group, 

where MOR means were higher for the nail holes on the tension edge. This group had smaller nail holes and this likely 

was the reason for these contradictory results. The other 

group mean MORs have percentage reductions of 14.8 for 

2 by 6 No. 2; 1.0 for 2 by 8 No. 2.; 18.4 for 11.6 2 by 8 SS; 

12.4 for 2 by 10 No. 2.; and 2 by 10 SS. Only the 2 by 8 and 

Table 18—Equivalent holes allowed compared to actual 

Grading rules (Standard No. 17)a Equiv. holes/ft allowed

1⁄2-in. diameter ruleb

Grade Size 

Max hole 

diameter (in.)

Equiv. holes over 

distance (ft) 

1/8 in. 

diameter 

3/16 in. 

diameter 

Actual

average 

(holes/ft)c

2 by 6 1.5 2 12.0 8.0 3.3 (4.4) 

2 by 8 2 2 16.0 10.7 2.5 (5.0) 

No. 2 

2 by 10 2.5 2 20.0 13.3 5.7 (8.3) 

2 by 6 1 4 4.0 2.7 3.3 (4.5) 

2 by 8 1.25 4 5.0 3.3 2.7 (5.5) 

SS

2 by 10 1.25 4 5.0 3.3 5.8 (7.8) 

a

 West Coast Lumber Inspection Bureau (2000). 

b

 Displacement defined as 1⁄2 the diameter according to the edge spike knot analogy. c

 Number in parentheses is absolute maximum number of holes per feet.

Figure 28—Cumulative distribution of edge-nail hole spacing by size–grade groups.
26

2 by 10 SS groups have a statistically significant difference 

at 95% confidence.

Recall that for the reclaimed lumber data set (Tables 8 and 

9), the difference between the SS grade and the No. 2 grade 

MOR mean is 1.58 ×103 lb/in2 on average for the three different sizes. Roughly speaking, this is approximately 

800 lb/in2 for each grade jump, No. 2 to No. 1, and No. 1 

to SS. The effect of the edge nails on strength could justify a 

grade reduction as indicated by the 2 by 6 No. 2 group 

(830 lb/in2 difference), 2 by 8 SS group (1,210 lb/in2 difference), and perhaps the 2 by 10 SS group (700 lb/in2). 

The differences between up (compression edge) and down 

(tension edge) in the 2 by 10 and 2 by 8 SS groups are consistent with the nail-hole spacing criteria discussed in the 

previous section. So, a one grade reduction might be justified for the presence of edge-nail holes (less than 1/8 in. 

diameter, no more than 21⁄2 in. deep), or prescriptive rules 

could specify that edge-nail holes would be allowed only on 

the compression edge.

Edge-nail Location

It is possible that edge-nail hole characteristics (size and 

spacing) are different for different geographical locations 

because of different construction techniques, environmental 

conditions, or usage. To investigate this, an additional 

analysis was performed. In this analysis, only SS grades 

were analyzed because of the confounding of MOR by the 

greater number (and size) of natural defects in the No. 2 

groups. The analysis focused on 2 by 8s and 2 by 10s, the 

sizes that showed statistically significant differences in 

MOR means between edge-nail holes tested up compared 

with down (Table 20).

Table 19—Effect of edge-nail hole orientation on lumber modulus of rupture (MOR) 

Mean COVc U vs D differenced

Size Grade Orientationa N

MOR

(×103 lb/in2

) SGb

MOR

(%)

SG dry 

(%)

MOR

(%)

SG 

(%)

Different

pairse

U 40 5.62 0.488 42.1 11.3 14.8 – 3.9 None 

D 47 4.79 0.507 43.1 10.6 0.83 – 0.02 

No. 2f

5.28 ×103 lb/in2g

N 19 5.76 0.486 36.3 12.6 

U 45 6.98 0.522 29.5 9.0 – 4.0 1.7 None 

D 44 7.26 0.513 31.9 12.0 – 0.28 0.01 

2 by 6 

SSh

7.03 ×103 lb/in2g

N 6 5.43 0.536 43.3 15.0 

U 101 4.86 0.476 44.4 10.0 1.0 – 1.5 None 

D 104 4.81 0.483 40.4 10.7 0.05 – 0.01 

N 7 4.76 0.509 54.9 14.0 

No. 2i

4.74 ×103 lb/in2g

B 22 4.31 0.472 42.5 9.6 

U 80 6.57 0.495 31.5 12.7 18.4 1.2 D & N 

D 75 5.36 0.489 41.4 12.4 1.21 0.01 D & U 

N 4 8.59 0.487 16.9 23.3 

2 by 8 

SSg

6.11 ×103 lb/in2f

B 3 7.64 0.579 19.2 20.3 

No. 2 U 52 4.26 0.491 42.7 12.9 12.4 – 2.0 None j

4.04 ×103 lb/in2g

D 39 3.73 0.501 41.7 13.0 0.53 – 0.01 

U 144 6.02 0.512 32.3 11.1 11.6 – 1.6 D & U 

D 135 5.32 0.520 28.7 10.2 0.70 – 0.01 

2 by 

10

SSi

5.65 ×103 lb/in2g 

N 4 4.61 0.491 31.7 12.2 

a U is edge-nail holes tested up, D is edge-nail holes tested down, B is edge-nail holes present on both edges, and N is No edge-

 nail holes present. 

b Specific gravity.

c

 Coefficient of variation is standard deviation/mean. d

 Percentage difference is (U – D) / (U) and difference = U – D. e

 For MOR, Tukey's studentized range (HSD) test at 95% or better confidence (SAS v8.2, GLM procedure). f

 One board in this group had nail holes on both edges (not reported). g

 As reported in Table 8, average group MOR for reclaimed lumber data set. 

h

 Edge-nail hole information not available for one board in each of these groups. i

 Edge-nail hole information not available for seven boards in each of these groups, one board contained holes on both edges 

 (not reported). 

j

Edge-nail hole information not available for two boards in this group. 

Research Paper FPL–RP–650
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

27

Mean MOR, SG, MOE, and nail-hole spacing for the different size–location–orientation groups are shown in Table 20. 

Also listed are differences in MOR and SG for the up compared with down edge-nail hole orientation. 

Results indicate that the only group that does not exhibit a 

substantial difference in MOR was the Washington 2 by 6s. 

This is consistent with the combined findings for the 

2 by 6 SS group in Table 20, and is likely explained 

because the holes were smaller for this group. 

The Washington 2 by 8 group showed a significant increase 

in mean MOR when placing the edge-nail holes on the compression edge, 940 lb/in.2 (Table 20). The cumulative distribution curves for MOR values of the up (compression edge) 

and down (tension edge) groups are shown in Figure 29. 

The tension-edge curve is shifted left (lower MOR) at the 

low end of the distribution until the very high end where the 

curves meet. This would imply that both the up and down 

groups contained some stronger boards in which nail holes 

did not affect MOR. Also note that a greater shift appears in 

the curves near the middle of the distribution as compared 

with the lower end. This could imply that nail-hole orientation has less of an effect on boards that contain other MORlowering defects.

For the same group, 2 by 8 Washington, mean MOE, SG, 

and nail-hole spacing are all very close for the up (compression edge) and down (tension edge) orientations (Table 20), 

which would imply negligible to no effects of these other 

variables on MOR mean. Of course, we would expect MOE 

to be close for the two groups, as this was the variable used 

to sort the two groups initially. 

Cumulative distributions of SG and MOE for the up and 

down groups are plotted in Figures 30 and 31, respectively. 

The SG curves are not the same shape, with the down curve 

shifted leftward (lower SG) at the extremes, and rightward 

(higher SG) near the center of the distribution. The curves 

do appear to average out throughout the rest of the distribution. However, recall that SG is not strong as a predictor of 

MOR as MOE. 

The Oakland 2 by 10 SS grade group exhibited very similar 

results. Mean MOR increased 910 lb/in2 or around 14% for 

the group of boards tested with the nail holes on the compression edge (Table 20 and Figure 32). As with the Washington 2 by 8s, mean SG, MOE, and nail-hole spacing were 

all very similar for the up and down groups (Figs 33, 34).

Minnesota 2 by 10s were the last SS grade group examined 

for edge-nail-hole orientation. This group also showed a 

shift in mean MOR of 600 lb/in2 (Table 20, Fig. 35), though 

not as much as the Oakland 2 by 10 SS group (910 lb/in2). 

Specific gravity or MOE have likely lessened the difference 

in MOR mean between up and down, as mean SG and MOE 

are larger for the down group (Table 20). This shift in SG 

and MOE can be seen in the upper portion of the cumulative 

distributions (Figs 36 and 37). Mean holes spacing, on the 

other hand, does compare well (Table 20).

The analysis was taken one step further to see if MOR was 

affected as greatly when nail-hole spacing was reduced or 

increased. Scatter plots were constructed with linear regression curves of MOR compared with nail-hole spacing for 

the 2 by 8 Washington SS group, 2 by 10 Oakland SS group, 

and the 2 by 10 Minnesota SS group (Figs 38, 39, and 40, 

respectively). Although correlation coefficients are low, the 

Washington and Oakland groups do exhibit a downward 

trend in MOR as nail-hole spacing decreases, greater for the 

Washington group (Figs 38 and 39). This trend was not seen 

in the Minnesota group (Fig. 40), which could also explain 

why the MOR means did not show a statistically significant 

difference.

Face Nails

Much of the lumber contained consistent face-nail-hole patterns (Code NF, Table 17, especially the 2 by 10s, which 

Table 20—Edge-nail hole orientation for Select Structural (SS) grade by size and location 

Mean COVc

 U vs D differenced

Location Size Orientationa N

MOR

(×103 lb/in2

) SGb

MOE

(×103 lb/in2

)

Nail spacing 

(holes/ft)

MOR

(%)

SG

(%)

MOR

(%)

SG 

(%)

2 by 6 U 16 6.41 0.508 2.57 3.26 26 6 – 6.4 2.8 

D 15 6.82 0.493 2.41 3.42 32 11 – 0.41 0.014 

U 63 6.15 0.485 2.25 2.67 31 13 15.3 0.6 

Washington

2 by 8 

D 62 5.21 0.482 2.26 2.70 43 12 0.94 0.003 

Oakland 2 by 10 U 86 6.35 0.527 2.79 5.95 30 10 14.4 – 0.1 

D 90 5.44 0.528 2.77 5.88 26 10 0.91 0.000 

Minnesota 2 by 10 U 28 5.73 0.492 1.98 5.25 28 12 10.5 – 2.8 

D 24 5.13 0.506 2.03 5.16 35 11 0.60 – 0.014 

a

 U is edge nail holes on compression edge (up), D is edge nail holes on tension edge (down). b

 Specific gravity. 

cCoefficient of variation is standard deviation/mean. d

 Percentage difference is (U – D) / (U) and difference is U – D.
28

Figure 29—Cumulative distribution of modulus of rupture (MOR) for up and down nail hole orientation for Washington 2 by 8 SS group.

Figure 30—Cumulative distribution of specific gravity (SG) for up and down nail hole orientation for 

Washington 2 by 8 SS group.

Research Paper FPL–RP–650
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

29

Figure 31—Cumulative distribution of modulus of elasticity (MOE) for up and down nail hole orientation for Washington 2 by 8 SS group.

Figure 32—Cumulative distribution of modulus of rupture (MOR) for up and down nail hole 

orientation for Oakland 2 by 10 SS group.
30

Figure 33—Cumulative distribution of specific gravity (SG) for up and down nail hole orientation for 

Oakland 2 by 10 SS group.

Figure 34—Cumulative distribution of modulus of elasticity (MOE) for up and down nail hole orientation for Oakland 2 by 10 SS group.

Research Paper FPL–RP–650
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

31

Figure 35—Cumulative distribution of modulus of rupture (MOR) for up and down nail hole orientation for Minnesota 2 by 10 SS group.

Figure 36—Cumulative distribution of specific gravity (SG) for up and down nail hole orientation for 

Minnesota 2 by 10 SS group.
32

Figure 38—Modulus of rupture (MOR) compared with up and down nail hole orientation for Washington 

2 by 8 SS group. NH/FT is nail holes per foot.

Research Paper FPL–RP–650

Figure 37—Modulus of rupture (MOR) compared with up and down nail hole orientation for Minnesota 

2 by 10 SS group. 
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

33

Figure 39—Modulus of rupture (MOR) compared with up and down nail hole orientations for Oakland 

2 by 10 SS group. NH/FT is nail holes per foot.

Figure 40—Modulus of rupture (MOR) compared with up and down nail hole orientation for Minnesota 

2 by 10 SS group. NH/FT is nail holes per foot.
34

Figure 41—Example of face nail holes in 2 by 10s 

from prior attachment of cross-bridging.

Figure 42—Example of face nail holes in 2 by 10s from 

prior attachment of wire-type mechanical hangers.

Research Paper FPL–RP–650

Table 21—Property comparison for 2 by 6 Oakland Select Structural 

(SS). Effect of face-nail hole orientation during testing 

Up Down Difference (%)a

Property N Mean

COV

(%)b N Mean

COV

(%)b Mean 

COV

(%)b

MOR (×103 lb/in2) 25 7.02 29.5 22 7.56 32.2 – 7.6 – 9.3 

MOE (×106 lb/in2) 25 2.14 15.6 22 2.28 18.3 – 6.3 – 17.4 

Specific gravity 25 0.531 9.6 22 0.533 12.3 – 0.4 – 28.1 

a Percentage difference is (up – down) / (up). 

bCoefficient of variation is standard deviation/mean.

contained nail holes from the prior attachment of cross 

bridging typically used to provide lateral stability and load 

distribution to the bending members (Fig. 41). These holes 

were typically found on the face, near both edges of the 

board. 

Pairs of face holes from the prior attachment of wire-type 

hangers commonly used to support mechanical piping were 

also found (Fig. 42). These holes were very near the center 

of the face, and stains from the hanger could be seen. These 

holes often times were caused through splits from wedging 

along the grain (Fig. 43). If these holes were near the end of 

a board, horizontal shear failures were more likely to occur 

(Fig. 43). The lower piece of the failed board in Figure 43 

has been turned to view the grain face of the split. Note the 

discoloration and additional staining at the fastener holes, 

which indicates the presence of a substantial through split 

prior to testing. 

Another type of repetitive face-nail hole was found in the 

Oakland 2 by 6 group of lumber. These boards were once 

wall studs that had blocking between each stud near the 

mid-height of the wall. The blocking was oriented such that 

the face of the blocking was at the outside face of the stud, 

with the 2-in. nominal dimension parallel to the 6-in. 

nominal dimension of the wall stud. This blocking created 

face-nail holes within 1-1/2 in. of the edge of the board 

(Fig. 44). This damage was so consistent that an experiment 

was designed exactly like the edge-nail holes, to see if placing this damage up or down during testing had an effect on 

mechanical properties. 

Table 21 summarizes the result of this experiment, showing mean properties and coefficients of variation (COV) 

for MOR, MOE, and SG for the up and down groups of 

boards. No statistical significance was found between the 

two groups. In fact, average MOR for the down group was 

approximately 8% larger for the group of boards tested with 

the face-nail holes down. 

These results illustrate that a nail hole, or tip of the crack, 

needs to be located at the region of highest stress to have 

an effect on fracture and hence bending strength. In other 

words, cracks have to form on the tension edge, where failure begins, for these nail holes to come into play. Also, these 

nail holes extended from one face directly to the other. This 

meant that an unaffected piece of wood still existed, below 

the holes, at the tension edge, providing an uninterrupted 

route for the greatest tension stress path. This is consistent 

with the simulated hole study by Falk and others (2003). In 

a few cases, the holes did extend from one face to the tension edge of the board (toenail holes, Code NT, Table 17), 

potentially initiating a split at the tension edge and causing 

the board to fail (Fig. 45).
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

35

Face Checks

Through splitting (Table 17) was a damage category with 

a related widespread phenomena—face checking. Face 

checking is typical in nearly every reclaimed lumber piece; 

however, the severity varies. To investigate the effect of face 

checks on lumber strength, boards were sorted based on a 

general ranking (1, 2, or 3) of face-checking severity: 1 was 

none to few, 2 was medium, and 3 was more severe. Face 

checking is not limited in existing grading rules for 

structural joists and planks. Figures 46 and 47 indicate medium checking and severe checking, respectively.

Only SS grade boards were examined, to avoid additional 

confounding effects for boards with known natural defects. 

The groups were also sorted by edge-nail hole orientation, 

because statistically significant effects were found for this 

variable as indicated in previous sections. Table 22 summarizes means and COV for MOR, MOE, and SG for the three 

different checking levels. 

Results indicate that checking levels do not affect MOE or 

SG. These variables were included to verify that they do not 

have an affect on MOR. Although statistically significant 

differences are not indicated, mean trends are interesting. 

For four out of the six groups, mean SG increases as the level of checking increases. Modulus of rupture does not show 

any consistent trends, although one group, Washington 

2 by 8 D, had the highest mean in the lowest check-level 

group.

Overall, there were no conclusive results from this analysis. It is therefore reasonable to assume that a limit on face 

checking specifically for reclaimed 2-by lumber may not be 

warranted. Note however, that Falk (1999b) found that severe heart checks in timbers reduced MOR by about 15%.

Damage Categories

As indicated in Table 17, three damage categories were 

established; nail-hole damage, through-splitting damage 

(a split completely through the board from face to face), 

and other mechanical damage. In the previous section, we 

looked at the effect of a specific damage type (for example, 

edge nails, face checks) on properties. In this section, we 

will look at the effect of these damage categories on properties. In essence, we are combining like damage into separate 

categories for comparison. For each of these categories, data 

were sorted by size, grade, and whether or not damage was 

involved in failure. 

Nail-Hole Damage

Table 23 shows the results for the nail-hole damage category. Note that percentage of differences are shown for the 

MOR mean, as well as the MOR mean adjusted for the percentage difference in MOE mean, in order to approximately 

capture the effect of stiffness (MOE) on MOR. Looking at 

the adjusted percentage differences, all the No. 2 boards 

with nails involved in the failure were stronger than the 

No. 2 boards where there was no damage involved with the 

failure. This might be explained by the fact that the board 

didn’t necessarily fail at the defect that placed it into the 

No. 2 grade. For the SS grades, 2 by 8 and 2 by 10 adjusted 

MOR percentage differences show that mean MOR is slightly lower (by 2.7% and 1.5%, respectively) for the boards 

with nails involved with failure than those boards where 

nails were not involved in the failure. For the 2 by 6 SS 

group, the opposite is shown. So, no clear trend is indicated 

for the effects of this category of nail-hole damage on MOR.

Figure 43—Example of failed 2 by 10 board where 

through splits from face nail holes caused horizontal 

shear failure.

Figure 44—Example of face-nail holes in Oakland 2 by 6 

wall studs from prior attachment of blocking.

Figure 45—Example of toenail holes in an Oakland 2 by 

6, potentially initiating a failure split.
36

Figure 46—Example of medium face checks. Figure 47—Example of severe face checks.

Research Paper FPL–RP–650

Table 22—Property mean comparisons by face-check level for SS grade 

Check level 1 Check level 2 Check level 3 Differencea

Size Location Orientb Property (units) N Mean

COV

(%)c N Mean

COV

(%)c N Mean 

COV

(%)c

1 to 2 

(%)d

2 to 3 

(%)d

MOR (×103 lb/in2) 5 6.00 33 54 5.14 44 3 5.18 43 14 – 1 

MOE (×106 lb/in2) 5 1.78 21 54 1.91 19 3 2.19 23 – 7 – 15 

D

Specific gravity 5 0.48 16 54 0.482 12 3 0.48 12 – 1 – 1 

MOR (×103

 lb/in2) 2 5.14 24 55 6.08 32 6 6.89 22 – 18 – 13 

MOE (×106

 lb/in2) 2 1.73 21 55 1.88 17 6 2.13 15 – 9 – 13 

2 by 8 Washington

U

Specific gravity 2 0.43 5 55 0.485 13 6 0.50 10 – 12 – 4 

MOR (×103

 lb/in2) 11 5.40 27 12 4.85 31 10 5.42 28 10 – 12 

MOE (×106

 lb/in2) 11 2.03 24 12 2.11 16 10 2.35 13 – 4 – 12 

D

Specific gravity 11 0.52 8 12 0.531 8 10 0.53 8 – 2 – 1 

MOR (×103

 lb/in2) 6 5.85 22 12 6.94 32 12 6.42 30 – 19 8 

MOE (×106

 lb/in2) 6 2.13 6 12 2.41 20 12 2.27 17 – 13 6 

Oakland

U

Specific gravity 6 0.52 8 12 0.544 11 12 0.54 5 – 4 1 

MOR (×103

 lb/in2) 6 5.22 46 14 5.10 34 4 5.93 27 2 – 16 

MOE (×106

 lb/in2) 6 2.10 19 14 1.97 17 4 2.31 11 6 – 17 

D

Specific gravity 6 0.48 11 14 0.495 12 4 0.55 4 – 2 – 11 

MOR (×103

 lb/in2) 6 5.45 22 15 6.13 27 7 5.10 35 – 12 17 

MOE (×106

 lb/in2) 6 1.85 12 15 2.07 9 7 1.90 16 – 12 8 

2 by 10 

Minnesota 

U

Specific gravity 6 0.46 4 15 0.502 12 7 0.49 15 – 8 2 

a

 Difference is (level 1 – level 2) / (level 1) or difference (%) = (level 2 – level 3) / (level 2). b

 Orientation of regular edge nail holes during testing: D, down; U, up. c

 Coefficient of variation = standard deviation/mean, also shaded cells indicate COV is higher than overall reclaimed lumber average 

 (Table 3). 

d

 Shaded cells indicate property mean decreases with the increase in split level. 
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

37

Through-Splitting Damage

The through-splitting damage category showed more consistent and anticipated results (Table 24). When adjusting 

the MOR mean for MOE, all the size and grade groups had 

lower MORs when through-splitting damage was involved 

in failure. The difference in strength ranged from approximately 9% for the 2 by 10 SS to approximately 27% for the 

2 by 6 No. 2. The trends are very consistent for each grade 

between the different sizes, with the difference increasing 

as the size decreases. For the No. 2 grade, differences are 

14.4%, 17.6%, and 26.7% for the 2 by 10, 2 by 8, and 2 by 

6 sizes, respectively. For SS grade, differences are 8.9%, 

20.0%, and 23.7% for the 2 by 10, 2 by 8, and 2 by 6 sizes, 

respectively. An explanation might be that for the same size 

and type of split, the defect becomes a larger percentage of 

the section as the size of the board decreases, hence having 

a greater decrease on MOR. Interestingly the SS grades for 

two of the three sizes show less of a difference, likely because the severity of splitting was not as great as for the 

No. 2 grade.

Other Mechanical Damage

Table 25 summarizes the same type of results for the other 

mechanical damage category. Recall that this category 

includes damage from mechanical gouging, man-made 

drilled holes, and cuts and notches. After adjusting for 

MOE, all the No. 2 grade MORs are greater for boards 

failing at damage. This likely carries the same explanation 

given for the nail-hole damage category. The No. 2 boards 

did not fail by the grade-determining defect, and the other 

mechanical defect is likely not as detrimental to strength as 

the grade-determining defect. All the SS grade groups show 

a decrease in MOR, according to the MOE adjustment, with 

Table 23—Property comparisons for nail-hole damage category 

No defecta Defectb Difference (%) 

With 

defect (%)c

Size Grade Property N Mean N Mean Meand MORe N

MOR (×103 lb/in2) 82 5.08 12 6.12 20.5 18.0 14.6 

MOE (×106 lb/in2) 80 1.75 12 1.80 2.5 15.0 

No. 2 

Specific gravity 82 0.49 12 0.48 – 2.0 14.6 

MOR (×103

 lb/in2) 70 7.02 11 8.18 16.5 6.4 15.7 

MOE (×106

 lb/in2) 68 2.07 11 2.28 10.2 16.2 

2 by 6 

SS

Specific gravity 70 0.51 11 0.55 8.0 15.7 

MOR (×103

 lb/in2) 83 4.51 17 5.21 15.5 2.2 20.5 

MOE (×106

 lb/in2) 32 1.63 9 1.85 13.4 28.1 

No. 2 

Specific gravity 83 0.48 17 0.51 6.2 20.5 

MOR (×103

 lb/in2) 125 6.14 30 6.10 – 0.6 – 2.7 24.0 

MOE (×106

 lb/in2) 96 1.89 24 1.93 2.1 25.0 

2 by 8 

SS

Specific gravity 125 0.49 30 0.51 4.5 24.0 

MOR (×103

 lb/in2) 57 3.78 10 5.18 37.1 26.3 17.5 

MOE (×106

 lb/in2) 57 1.75 10 1.94 10.8 17.5 

No. 2 

Specific gravity 57 0.50 10 0.52 2.9 17.5 

MOR (×103

 lb/in2) 151 5.81 54 5.77 – 0.6 – 1.5 35.8 

MOE (×106

 lb/in2) 151 2.16 54 2.18 0.9 35.8 

2 by 10 

SS

Specific gravity 151 0.51 54 0.52 2.2 35.8 

All MOR 568 134 23.6 

MOE 484 120 24.8 

a

 No apparent damage defect involved in failure. b

 Nail hole defect involved in failure. 

cc

 Percentage of pieces with defects involved in failure out of all pieces within size grade group. d

 Percentage difference of mean MOR is (defect – no defect) / (no defect). 

e

 Percentage difference of mean MOR adjusted for MOE is [(MORDefect – MORNo Defect) / MORNo Defect] – 

 [(MOEDefect – MOENo Defect) / MOENo Defect]

C
38

the other mechanical damage involved, ranging from 14.5% 

for the 2 by 6 group to 25.4% for the 2 by 10 group. This 

trend is opposite to what was shown for the throughsplitting damage group.

The magnitude or size of the defect was not evaluated for all 

these analyses. Rather, we were only able to document if the 

damage was involved in the failure, although not necessarily initiating it. Also, involvement in failure carries a fairly 

broad definition. Simply examining a failed board makes it 

difficult to make that exact determination, though in many 

cases it may be deduced with relative certainty. Also, the 

sample sizes in this analysis were fairly small, and given the 

inherent variability of wood, this makes most conclusions 

gathered from this analysis rather weak. Last, other effects 

known to have statistically significant effects on MOR, such 

as location, edge-nail hole orientation, and damage downgrading, could not be included in the sorting as the sample 

sizes would have become too small. 

Full-Size Lumber Failure Types

Up to this point, we have focused on comparing lumber 

failures caused by damage to “the rest of the population” 

of lumber. In this section, we will look more specifically 

at how these damage failures compare to the more typical 

types of lumber failures (e.g, wood tension, knots, SOG, see 

Table 2). Tension-type failures are broken down into four 

categories according to the failure defect (clear wood, knot, 

damage, and slope of grain). 

No. 2 Grade

First, we will look at the No. 2 grade, then SS. The frequency of failure types for all sizes of the No. 2 grade are summarized in Table 26. Note that three of the tension failure 

types (Table 27, code 2, 3, and 4) match specific GDDs such 

as knots, damage, and slope of grain (Table 28, code 3, 5, 

and 7). Comparing the frequencies for all sizes, there were 

about 13% more knot failures, approximately 26% fewer 

Research Paper FPL–RP–650

Table 24—Point-damage mean property comparisons for the through-splitting 

damage category 

No defecta Defectb Difference (%) 

With 

defect (%)c

Size Grade Property N Mean N Mean Mean (%)d MOE (%)e N

MOR (×103 lb/in2) 82 5.08 6 4.95 – 2.5 – 26.0 7.3 

MOE (×106 lb/in2) 80 1.75 6 2.18 24.2 7.5 

No. 2 

Specific gravity 82 0.49 6 0.57 16.5 7.3 

MOR (×103

 lb/in2) 70 7.02 12 6.44 – 8.3 – 23.7 17.1 

MOE (×106

 lb/in2) 68 2.07 12 2.39 15.4 17.6 

2 by 6 

SS

Specific gravity 70 0.51 12 0.56 9.4 17.1 

MOR (×103

 lb/in2) 83 4.51 5 5.35 18.6 – 17.6 6.0 

MOE (×106

 lb/in2) 32 1.63 1 2.22 36.1 3.1 

No. 2 

Specific gravity 83 0.48 5 0.48 1.0 6.0 

MOR (×103

 lb/in2) 125 6.14 5 5.57 – 9.2 – 20.0 4.0 

MOE (×106

 lb/in2) 96 1.89 4 2.09 10.7 4.2 

2 by 8 

SS

Specific gravity 125 0.49 5 0.56 15.1 4.0 

MOR (×103

 lb/in2) 57 3.78 4 3.50 – 7.4 – 14.4 7.0 

MOE (×106

 lb/in2) 57 1.75 4 1.88 7.0 7.0 

No. 2 

Specific gravity 57 0.50 4 0.49 – 2.6 7.0 

MOR (×103

 lb/in2) 151 5.81 45 5.55 – 4.4 – 8.9 29.8 

MOE (×106

 lb/in2) 151 2.16 45 2.26 4.5 29.8 

2 by 10 

SS

Specific gravity 151 0.51 45 0.53 4.3 29.8 

All MOR 568 77 13.6 

MOE 484 72 14.9 

a

 No apparent damage defect involved in failure. b

 Through-splitting defect involved in failure. 

c

 Percentage of pieces with nail hole defects involved in failure out of all pieces within size grade group. d

 Percentage difference of mean MOR is (defect – no defect) / (no defect). 

e

 Percentage difference of mean MOR adjusted for MOE is [(MOR defect – MOR no defect) / MOR no defect] – 

 [(MOE defect – MOE no defect) / MOE no defect].
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

39

damage failures, and about 5% more slope of grain failures 

than the GDDs would indicate. 

When comparing mean MOR, data were sorted in two 

groups, one in which the failure defect matched the gradedetermining defect and another that did not. This was done 

to obtain a measure of how much strength could differ, 

according to failure type, depending on whether or not the 

GDD caused failure. In theory, the group that failed by the 

grade-determining defect should exhibit lower MOR, assuming SG is similar.

Mean MOR and SG are reported according to failure type 

and whether or not the failure defect matched the visual 

GDD. Tables 29, 30, and 31 indicate this comparison for 

the three sizes of lumber. The following observations are 

made:

Tension-wood failures are typically in clear wood with no 

defects involved. These group means compare very well to 

the comparable size SS overall group averages (Table 8); 

mean MORs of 7.07, 6.14, and 5.97 ×103 lb/in2 compared to 

7.03, 6.11, and 5.65 ×103 lb/in2 for the 2 by 6, 2 by 8, and 

2 by 10 sizes, respectively.

Differences in MOR for boards with knot failures to boards 

whose grade-determining defect were knots are 0.64, 0.79, 

and 0.81 ×103 lb/in2 for the 2 by 6, 2 by 8, and 2 by 10 sizes, 

respectively.

Mean MOR for boards with horizontal shear failures 

were higher than the overall mean MOR for the 2 by 6 

(9.40 ×103 lb/in2 compared with 5.28 ×103 lb/in2) and 2 by 8 

(5.80 ×103 lb/in2 compared with 4.79 ×103 lb/in2) sizes and 

right at the mean for the 2 by 10 (4.03 ×103 lb/in2 compared 

with 4.04 ×103 lb/in2) size.

Boards with compression failures exhibited a greater mean 

MOR than the overall mean MOR for all sizes.

Table 25—Point damage mean property comparisons for other mechanical 

damage category 

No defecta Defectb Difference (%) 

With 

defect (%)c

Size Grade Property N Mean N Mean Mean (%)d MOR (%)e N

MOR (×103 lb/in2) 82 5.08 7 6.36 25.2 20.8 8.5 

MOE (×106 lb/in2) 80 1.75 5 1.83 4.4 6.3 

No. 2 

Specific gravity 82 0.49 7 0.49 – 0.7 8.5 

MOR (×103

 lb/in2) 70 7.02 3 5.30 – 24.5 – 14.5 4.3 

MOE (×106

 lb/in2) 68 2.07 3 1.86 – 10.0 4.4 

2 by 6 

SS

Specific gravity 70 0.51 3 0.46 – 9.0 4.3 

MOR (×103

 lb/in2) 83 4.51 2 4.55 0.9 0.3 2.4 

MOE (×106

 lb/in2) 32 1.63 1 1.64 0.6 3.1 

No. 2 

Specific gravity 83 0.48 2 0.49 1.7 2.4 

MOR (×103

 lb/in2) 125 6.14 1 5.21 – 15.0 – 19.4 0.8 

MOE (×106

 lb/in2) 96 1.89 1 1.97 4.4 1.0 

2 by 8 

SS

Specific gravity 125 0.49 1 0.51 3.9 0.8 

MOR (×103

 lb/in2) 57 3.78 7 4.30 13.8 12.4 12.3 

MOE (×106

 lb/in2) 57 1.75 7 1.78 1.4 12.3 

No. 2 

Specific gravity 57 0.50 7 0.52 2.8 12.3 

MOR (×103

 lb/in2) 151 5.81 4 5.23 – 10.0 – 25.4 2.6 

MOE (×106

 lb/in2) 151 2.16 4 2.50 15.4 2.6 

2 by 10 

SS

Specific gravity 151 0.51 4 0.59 14.5 2.6 

All MOR 568 24 4.2 

MOE 484 21 4.3 

a

 No apparent damage defect involved in failure. b

 Other mechanical damage defect involved in failure. c

 Percentage of pieces with nail hole defects involved in failure out of all pieces within size–grade group. d

 Difference of mean (%) MOR is (defect – no defect) / (no defect). 

e

 Difference of mean (%) MOR adjusted for MOE is [(MOR defect – MOR no defect) / MOR no defect] – 

 [(MOE defect – MOE no defect) / MOE no defect].
40

Tension at knot failures have the lowest mean MOR for the 

2 by 6 and 2 by 8 sizes and the second lowest (slope of grain 

failures were weaker) for the 2 by 10 sizes. In all cases, 

MOR for boards failing at knots in tension is about 80% of 

the overall group mean.

Select Structural Grade

The frequency of the various failure types for all sizes of the 

SS grade is shown in Table 31. Knot-related tension failures 

dominate at about 33%, with clear-wood tension failure following at about 17%. Interestingly, horizontal shear failures 

occurred about 7% of the time in the No. 2 grade, but increased to about 12% in the SS grade for all sizes. However, 

shear failures were as high as 18% for the 2 by 10 SS 

( Table 32). Horizontal shear failures are known to be relatively infrequent in testing mill-produced lumber (~1% to 

2% of the time), so either the shear strength may be reduced 

or, more likely, splitting from damage and drying has resulted in a greater frequency of this type of failure. We will 

discuss this in detail later.

The frequency of failures from damage also increased in 

the SS grade, up from about 8% in the No. 2 grade to about 

14% in the SS grade. This makes sense, as the fewer natural 

defects in the higher grade increase the likelihood of damage in board failure. 

Mean MOR and SG are also reported by failure type for the 

SS boards. The following observations are made:

• Compression failures have the greatest mean MOR for the 

2 by 6 and 2 by 8 groups, and the second greatest for the 

2 by 10 group.

• Knot failures in tension have the lowest mean MOR for 

all sizes.

Research Paper FPL–RP–650

Table 27—Distribution of grade determining defects (GDD) of No. 2 lumber 

All sizes 2 by 6 2 by 8 2 by 10 

and

locations Fort Ord Oakland Washington Fort Ord Washington Oakland Minnesota

GDD (code) N % N % N % N % N % N % N % N %

Shake (1) 31 7.3 3 4.2 — — — — 12 6.1 3 7.0 11 20.8 2 8.0

Splits (2) 11 2.6 1 1.4 — — 1 5.0 7 3.5 — — — — 2 8.0

Knots (3) 173 40.6 32 45.1 9 56.3 16 80.0 69 34.8 28 65.1 7 13.2 12 48.0

Damage (5) 147 34.5 29 40.8 3 18.8 2 10.0 84 42.4 7 16.3 18 34.0 4 16.0

Wane (6) 5 1.2 — — 1 6.3 — — 1 0.5 1 2.3 1 1.9 1 4.0

Slope of grain (7) 30 7.0 1 1.4 2 12.5 — — 8 4.0 2 4.7 16 30.2 1 4.0

Warp (8) 1 0.2 1 1.4 — — — — — — — — — — — —

Checks (9) 2 0.5 — — — — — — 2 1.0 — — — — — —

Other (10) 26 6.1 4 5.6 1 6.3 1 5.0 15 7.6 2 4.7 — — 3 12.0

Total 426 100 71 100 16 100 20 100 198 100 43 100 53 100 25 100 

Table 26—Distribution of failure codes for No. 2 lumber 

All sizes 2 by 6 2 by 8 2 by 10 

and

locations Fort Ord Oakland Washington Fort Ord Washington Oakland Minnesota Failure code 

(Table 2) N % N % N % N % N % N % N % N %

Tension-wood (1) 58 13.2 10 14.1 2 12.5 3 15.0 29 14.6 7 16.3 5 9.4 2 5.0

Tension-knot (2) 234 53.1 40 56.3 8 50.0 14 70.0 102 51.5 25 58.1 25 47.2 20 50.0

Tension-damage (3) 36 8.2 5 7.0 3 18.8 1 5.0 10 5.1 7 16.3 5 9.4 5 12.5

Tension-SOG (4) 56 12.7 10 14.1 2 12.5 — — 27 13.6 1 2.3 9 17.0 7 17.5

Compression (5) 21 4.8 2 2.8 1 6.3 2 10.0 11 5.6 — — 4 7.5 1 2.5

Horizontal shear (6) 32 7.3 3 4.2 — — — — 16 8.1 3 7.0 5 9.4 5 12.5

Invalid test (7) 2 0.5 — — — — — — 2 1.0 — — — — — —

Other (8) 2 0.5 1 1.4 — — — — 1 0.5 — — — — — —

Total 441 100 71 100 16 100 20 100 198 100 43 100 53 100 40 100 
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

41

Table 28—Mean properties by failure code for 2 by 6 No. 2 grade 

Meanb All locations Fort Ord Oakland Washington

Failure code 

(Table 2) 

Same 

as visual 

grade (GDDa

)

MOR

(×103

 lb/in2) SGc N % N % N % N %

Tension-wood (1) N 7.07 0.497 15 14.2 10 14.3 2 12.5 3 15.0 

N 4.59 0.489 19 17.9 14 20.0 2 12.5 3 15.0

Y 3.95 0.487 43 40.6 26 37.1 6 37.5 11 55.0

Tension-knot (2) 

Combined 4.15 0.488 62 58.5 40 57.1 8 50.0 14 70.0

N 6.60 0.471 4 3.8 2 2.9 1 6.3 1 5.0

Y 6.88 0.476 5 4.7 3 4.3 2 12.5 — — 

Tension-damage (3) 

Combined 6.75 0.473 9 8.5 5 7.1 3 18.8 1 5.0

N 6.01 0.488 9 8.5 9 12.9 — — — —

Y 4.03 0.569 3 2.8 1 1.4 2 12.5 — —

Tension-slope-ofgrain (4) 

Combined 5.51 0.508 12 11.3 10 14.3 2 12.5 — —

N 8.86 0.535 3 2.8 2 2.9 1 6.3 — —

Y 5.99 0.636 2 1.9 — — — — 2 10.0

Compression (5) 

Combined 7.71 0.575 5 4.7 2 2.9 1 6.3 2 10.0

Horizontal shear (6) N 9.40 0.551 3 2.8 3 2.9 — — — —

Total 5.28 0.496 106 100 70 100 16 100 20 100 

a Grade-determining defect. 

b Means shown are same as reported in Table 8. 

c Specific gravity. 

Table 28—Mean properties by failure code for 2 by 6 No. 2 grade 

Meanb All locations Fort Ord Oakland Washington

Failure code 

(Table 2) 

Same 

as visual 

grade (GDDa

)

MOR

(×103

 lb/in2) SGc N % N % N % N %

Tension-wood (1) N 7.07 0.497 15 14.2 10 14.3 2 12.5 3 15.0 

N 4.59 0.489 19 17.9 14 20.0 2 12.5 3 15.0

Y 3.95 0.487 43 40.6 26 37.1 6 37.5 11 55.0

Tension-knot (2) 

Combined 4.15 0.488 62 58.5 40 57.1 8 50.0 14 70.0

N 6.60 0.471 4 3.8 2 2.9 1 6.3 1 5.0

Y 6.88 0.476 5 4.7 3 4.3 2 12.5 — — 

Tension-damage (3) 

Combined 6.75 0.473 9 8.5 5 7.1 3 18.8 1 5.0

N 6.01 0.488 9 8.5 9 12.9 — — — —

Y 4.03 0.569 3 2.8 1 1.4 2 12.5 — —

Tension-slope-ofgrain (4) 

Combined 5.51 0.508 12 11.3 10 14.3 2 12.5 — —

N 8.86 0.535 3 2.8 2 2.9 1 6.3 — —

Y 5.99 0.636 2 1.9 — — — — 2 10.0

Compression (5) 

Combined 7.71 0.575 5 4.7 2 2.9 1 6.3 2 10.0

Horizontal shear (6) N 9.40 0.551 3 2.8 3 2.9 — — — —

Total 5.28 0.496 106 100 70 100 16 100 20 100 

a Grade-determining defect. 

b Means shown are same as reported in Table 8. 

c Specific gravity. 

Table 29—Mean properties by failure code for 2 by 8 No. 2 grade 

Meanb All locations Fort Ord Washington

Failure code 

(Table 2) 

Same 

as visual 

grade (GDDa

)

MOR

(×103

 lb/in2) SGc N % N % N %

Tension-wood (1) N 6.14 0.478 35 14.8 29 14.9 6 14.0 

N 4.28 0.468 64 27.0 56 28.9 8 18.6 

Y 3.49 0.466 63 26.6 46 23.7 17 39.5 

Tension-knot (2) 

Combined 3.89 0.467 127 53.6 102 52.6 25 58.1 

N 4.70 0.509 11 4.6 5 2.6 6 14.0 

Y 5.06 0.503 6 2.5 5 2.6 1 2.3 

Tension-damage (3) 

Combined 4.83 0.507 17 7.2 10 5.2 7 16.3 

N 5.48 0.513 22 9.3 21 10.8 1 2.3 

Y 4.76 0.515 6 2.5 5 2.6 1 2.3 

Tension-slope-ofgrain (4) 

Combined 5.33 0.513 28 11.8 26 13.4 2 4.7 

Compression (5) N 7.18 0.475 11 4.6 11 5.7 

N 6.03 0.493 15 6.3 14 7.2 1 2.3 

Y 4.96 0.523 4 1.7 2 1.0 2 4.7 

Horizontal shear (6) 

Combined 5.80 0.500 19 8.0169 16 8.25 3 6.98

Total 4.79 0.480 237 100 194 100 43 100 

a Grade-determining defect. 

b Means shown are same as reported in Table 8. 

c Specific gravity. 

Table 29—Mean properties by failure code for 2 by 8 No. 2 grade 

Meanb All locations Fort Ord Washington

Failure code 

(Table 2) 

Same 

as visual 

grade (GDDa

)

MOR

(×103

 lb/in2) SGc N % N % N %

Tension-wood (1) N 6.14 0.478 35 14.8 29 14.9 6 14.0 

N 4.28 0.468 64 27.0 56 28.9 8 18.6 

Y 3.49 0.466 63 26.6 46 23.7 17 39.5 

Tension-knot (2) 

Combined 3.89 0.467 127 53.6 102 52.6 25 58.1 

N 4.70 0.509 11 4.6 5 2.6 6 14.0 

Y 5.06 0.503 6 2.5 5 2.6 1 2.3 

Tension-damage (3) 

Combined 4.83 0.507 17 7.2 10 5.2 7 16.3 

N 5.48 0.513 22 9.3 21 10.8 1 2.3 

Y 4.76 0.515 6 2.5 5 2.6 1 2.3 

Tension-slope-ofgrain (4) 

Combined 5.33 0.513 28 11.8 26 13.4 2 4.7 

Compression (5) N 7.18 0.475 11 4.6 11 5.7 

N 6.03 0.493 15 6.3 14 7.2 1 2.3 

Y 4.96 0.523 4 1.7 2 1.0 2 4.7 

Horizontal shear (6) 

Combined 5.80 0.500 19 8.0169 16 8.25 3 6.98

Total 4.79 0.480 237 100 194 100 43 100 

a Grade-determining defect. 

b Means shown are same as reported in Table 8. 

c Specific gravity. 
42

Research Paper FPL–RP–650

Table 30—Mean properties by failure code for 2 by 10 No. 2 grade 

Meanb All locations Oakland Minnesota 

Failure code 

(Table 2) 

Same 

as visual 

grade (GDDa

)

MOR

(×103

 lb/in2) SGc N % N % N %

Tension-wood (1) N 5.97 0.531 5 7.5 4 8.9 1 4.5 

N 3.77 0.497 22 32.8 14 31.1 8 36.4

Y 2.96 0.492 16 23.9 11 24.4 5 22.7

Tension-knot (2) 

Combined 3.43 0.495 38 56.7 25 55.6 13 59.1

N 4.38 0.488 5 7.5 3 6.7 2 9.1

Y 5.18 0.504 4 6.0 2 4.4 2 9.1

Tension-damage (3) 

Combined 4.74 0.495 9 13.4 5 11.1 4 18.2

Tension-SOGd

 (4) N 3.34 0.525 11 16.4 9 20.0 2 9.1 

N 8.66 0.583 2 3.0 2 4.4 0.0

Y 6.00 0.540 2 3.0 2 4.4 0.0

Compression (5) 

Combined 7.33 0.562 4 6.0 4 8.9 0 0.0

N 4.61 0.493 5 7.5 2 4.4 3 13.6

Y 3.32 0.476 4 6.0 3 6.7 1 4.5

Horizontal shear (6) 

Combined 4.03 0.485 9 13.4 5 11.1 4 18.2

Total 4.04 0.494 67 100 45 100 22 100 

a

Grade-determining defect. 

b Means shown are same as reported in Table 8. 

c Specific gravity. 

d Slope of grain.

Table 30—Mean properties by failure code for 2 by 10 No. 2 grade 

Meanb All locations Oakland Minnesota 

Failure code 

(Table 2) 

Same 

as visual 

grade (GDDa

)

MOR

(×103

 lb/in2) SGc N % N % N %

Tension-wood (1) N 5.97 0.531 5 7.5 4 8.9 1 4.5 

N 3.77 0.497 22 32.8 14 31.1 8 36.4

Y 2.96 0.492 16 23.9 11 24.4 5 22.7

Tension-knot (2) 

Combined 3.43 0.495 38 56.7 25 55.6 13 59.1

N 4.38 0.488 5 7.5 3 6.7 2 9.1

Y 5.18 0.504 4 6.0 2 4.4 2 9.1

Tension-damage (3) 

Combined 4.74 0.495 9 13.4 5 11.1 4 18.2

Tension-SOGd

 (4) N 3.34 0.525 11 16.4 9 20.0 2 9.1 

N 8.66 0.583 2 3.0 2 4.4 0.0

Y 6.00 0.540 2 3.0 2 4.4 0.0

Compression (5) 

Combined 7.33 0.562 4 6.0 4 8.9 0 0.0

N 4.61 0.493 5 7.5 2 4.4 3 13.6

Y 3.32 0.476 4 6.0 3 6.7 1 4.5

Horizontal shear (6) 

Combined 4.03 0.485 9 13.4 5 11.1 4 18.2

Total 4.04 0.494 67 100 45 100 22 100 

a

Grade-determining defect. 

b Means shown are same as reported in Table 8. 

c Specific gravity. 

d Slope of grain.

Table 31—Distribution of failure codes for SS lumber 

All sizes 2 by 6 2 by 8 2 by 10 

and

 locations Fort Ord Oakland Washington Fort Ord Washington Oakland Minnesota Failure code 

(Table 2) N % N % N % N % N % N % N % N %

Tension-wood (1) 94 17.1 4 33.3 16 34.0 10 27.0 6 16.2 28 22.2 17 8.6 13 13.8

Tension-knot (2) 184 33.5 1 8.3 6 12.8 12 32.4 5 13.5 67 53.2 50 25.4 43 45.7

Tension-damage (3) 79 14.4 1 8.3 11 23.4 4 10.8 4 10.8 19 15.1 36 18.3 4 4.3

Tension-SOGa

 (4) 70 12.7 4 33.3 8 17.0 4 10.8 8 21.6 5 4.0 28 14.2 13 13.8

Compression (5) 50 9.1 2 16.7 4 8.5 3 8.1 8 21.6 4 3.2 22 11.2 7 7.4

Horizontal shear (6) 65 11.8 — — 2 4.3 3 8.1 6 16.2 2 1.6 39 19.8 13 13.8

Invalid test (7) 1 0.2 — — — — 1 2.7 — — — — — — — —

Other (8) 7 1.3 — — — — — — — — 1 0.8 5 2.5 1 1.1

Total 550 100 12 100 47 100 37 100 37 100 126 100 197 100 94 100 

 a Slope-of-grain.
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

43

• About 18% (52 of 291) of the 2 by 10s failed in horizontal shear; however, these boards exhibited a greater MOR 

than the rest of the 2 by 10s (5.95 ×103 lb/in2 compared 

with 5.65 ×103 lb/in2).

Analysis of Full-Size Lumber 

by Grade

Up to this point, all analyses were by grade and size. No 

adjustments were made to the data other than to correct for 

MC. Though useful information was developed, analyzing cells of data by size and grade resulted in data sets that 

could be rather small and reduced the statistical confidence 

of the results. In this section, the full-size lumber data have 

been adjusted to a common size (2 by 8) and a variety of 

analyses performed. Whereas some of these analyses duplicate those performed earlier, they involve more data and 

should provide more confidence in the results. No adjustments for location or SG were made. Only MOR is reported. 

As indicated in Table 33, a comparison of the bending 

strength of all lumber, the combined Douglas-fir and larch 

(L) data and lumber of other species is made. Results 

indicate that the mean MOR of the all grades/sizes data set 

is only about 2% lower than the DF/L alone. Further, a statistical significance test indicates that the Douglas-fir and 

larch lumber MOR is significantly different than the other 

species MOR. A statistical significance test to compare the 

all grades/sizes data set and the Douglas-fir and larch data 

set would be illogical because the Douglas-fir and larch data 

are a subset of the all grades/sizes data set. Assuming that 

the species variability found in this study is representative 

of other deconstruction sites, these results indicate that the 

inclusion of species other than Douglas-fir and larch (at least 

up to the proportion present in this data set) does not appreciably affect either the mean or 5th percentile MOR estimate 

of the whole population of lumber. 

Table 34 indicates the results of analyzing all the full-size 

lumber data by grade. As expected, there is a significant 

difference in the mean and 5th percentile MOR in the two 

grades, with the SS grade significantly higher than the 

No. 2 grade.

Table 35 shows the results of sorting the size-adjusted fullsize lumber data by failure type. As indicated in the table, 

Table 32—Mean properties by failure code and size for Select Structural (SS) grade 

Mean a All locations Fort Ord Oakland Washington Minnesota

Size 

Failure code 

(Table 2) 

MOR

(×103

 lb/in2) SG N % N % N % N % N %

Tension-wood (1) 7.48 0.52 30 31.6 4 33.3 16 34.0 10 27.8 — —

Tension-knot (2) 5.14 0.51 19 20.0 1 8.3 6 12.8 12 33.3 — —

Tension-damage (3) 7.20 0.54 16 16.8 1 8.3 11 23.4 4 11.1 — —

Tension-SOGb (4) 6.68 0.49 16 16.8 4 33.3 8 17.0 4 11.1 — —

Compression (5) 9.43 0.51 9 9.5 2 16.7 4 8.5 3 8.3 — —

Horizontal shear (6) 7.75 0.56 5 5.3 0 0.0 2 4.3 3 8.3 — —

2 by 6 

Total 7.03a 0.52a 95 100 12 100 47 100 36 100 — —

Tension-wood (1) 6.71 0.50 34 21.0 6 16.2 — — 28 22.4 — —

Tension-knot (2) 5.36 0.48 72 44.4 5 13.5 — — 67 53.6 — —

Tension-damage (3) 6.17 0.51 23 14.2 4 10.8 — — 19 15.2 — —

Tension-SOG (4) 5.77 0.51 13 8.0 8 21.6 — — 5 4.0 — —

Compression (5) 8.67 0.51 12 7.4 8 21.6 — — 4 3.2 — —

Horizontal shear (6) 6.55 0.52 8 4.9 6 16.2 — — 2 1.6 — —

2 by 8 

Total 6.11a 0.49a 162 100 37 100 — — 125 100 — —

Tension-wood (1) 6.68 0.52 30 10.3 — — 17 8.6 — — 13 13.8

Tension-knot (2) 4.56 0.49 93 32.0 — — 50 25.4 — — 43 45.7

Tension-damage (3) 5.49 0.53 40 13.7 — — 36 18.3 — — 4 4.3

Tension-SOG (4) 5.55 0.52 41 14.1 — — 28 14.2 — — 13 13.8

Compression (5) 7.44 0.54 29 10.0 — — 22 11.2 — — 7 7.4

Horizontal shear (6) 5.95 0.52 52 17.9 — — 39 19.8 — — 13 13.8

Other (8) 7.84 0.51 6 2.1 — — 5 2.5 — — 1 1.1

2 by 10 

Total 5.65 0.51a 291 100 — — 197 100 — — 94 100 a Means shown are same as reported in Table 8. 

b Slope of grain. 

Table 32—Mean properties by failure code and size for Select Structural (SS) grade 

Mean a All locations Fort Ord Oakland Washington Minnesota

Size 

Failure code 

(Table 2) 

MOR

(×103

 lb/in2) SG N % N % N % N % N %

Tension-wood (1) 7.48 0.52 30 31.6 4 33.3 16 34.0 10 27.8 — —

Tension-knot (2) 5.14 0.51 19 20.0 1 8.3 6 12.8 12 33.3 — —

Tension-damage (3) 7.20 0.54 16 16.8 1 8.3 11 23.4 4 11.1 — —

Tension-SOGb (4) 6.68 0.49 16 16.8 4 33.3 8 17.0 4 11.1 — —

Compression (5) 9.43 0.51 9 9.5 2 16.7 4 8.5 3 8.3 — —

Horizontal shear (6) 7.75 0.56 5 5.3 0 0.0 2 4.3 3 8.3 — —

2 by 6 

Total 7.03a 0.52a 95 100 12 100 47 100 36 100 — —

Tension-wood (1) 6.71 0.50 34 21.0 6 16.2 — — 28 22.4 — —

Tension-knot (2) 5.36 0.48 72 44.4 5 13.5 — — 67 53.6 — —

Tension-damage (3) 6.17 0.51 23 14.2 4 10.8 — — 19 15.2 — —

Tension-SOG (4) 5.77 0.51 13 8.0 8 21.6 — — 5 4.0 — —

Compression (5) 8.67 0.51 12 7.4 8 21.6 — — 4 3.2 — —

Horizontal shear (6) 6.55 0.52 8 4.9 6 16.2 — — 2 1.6 — —

2 by 8 

Total 6.11a 0.49a 162 100 37 100 — — 125 100 — —

Tension-wood (1) 6.68 0.52 30 10.3 — — 17 8.6 — — 13 13.8

Tension-knot (2) 4.56 0.49 93 32.0 — — 50 25.4 — — 43 45.7

Tension-damage (3) 5.49 0.53 40 13.7 — — 36 18.3 — — 4 4.3

Tension-SOG (4) 5.55 0.52 41 14.1 — — 28 14.2 — — 13 13.8

Compression (5) 7.44 0.54 29 10.0 — — 22 11.2 — — 7 7.4

Horizontal shear (6) 5.95 0.52 52 17.9 — — 39 19.8 — — 13 13.8

Other (8) 7.84 0.51 6 2.1 — — 5 2.5 — — 1 1.1

2 by 10 

Total 5.65 0.51a 291 100 — — 197 100 — — 94 100 a

Means shown are same as reported in Table 8. 

b Slope of grain. 
44

Research Paper FPL–RP–650

Table 33—Bending strength of reclaimed lumber by species mixed sizea

and grade 

N

Mean MOR 

(×103

 lb/in2)

Statistical

difference

5th percentile MOR 

(×103 lb/in2)

Statistical 

difference

All grades, sizes 1,078 5.56 2.36 

DF/Lb 991 5.64 Ac 2.45 Ab

Other species 87 4.61 Bc 1.49 Bb

a All full-size lumber data adjusted to 2 by 8 size. 

b Douglas-fir and larch.

c

Differences indicate a significance level at < 0.0001.

Table 34—Bending strength of all sizes by grade, 

Douglas-fir and larch only 

N

Mean MOR 

(×103

 lb/in2)

a

Statistical 

difference

5th percentile MOR 

(×103

 lb/in2)

SS 550 6.32 Ab 3.09 

No. 2 441 4.79 Bb 2.09 

a

All full-size lumber data adjusted to 2 by 8 size. 

b Differences indicate a significance level at < 0.0001. 

lumber exhibiting compression failures resulted in the 

highest MORs, followed by wood tension, shear, damage, 

SOG, and knots. This ranking was consistent for both grades 

and when grades were mixed. As was indicated in earlier 

analysis, knot failures are the critical lumber characteristic 

in terms of bending strength. Note also that knot failures are 

the most common failure type, making up nearly half the 

failures. As a group, SOG failures produce the second lowest MORs, likely due to the effect of splits on strength. Also, 

note that shear failures are common, making up about 9% 

of all failures. Shear failures made up about 12% of failures 

in the SS grade and a much lower 6% in the No. 2 grade. 

These findings are consistent with the results of the earlier 

analysis by size and grade.

Table 36 groups the bending strength of size-adjusted fullsized reclaimed lumber by GDD. Because the lumber in 

the SS grade had no GDD, only the No. 2 grade is shown. 

Interestingly, the lowest strength boards were those that had 

splits as the GDD. The next lowest in strength are knots. 

This is reasonably consistent with the findings of Table 36. 

Damage determined grade for almost half the No. 2 grade; 

however, damage was involved in the failure for 9% of the 

lumber. This might suggest that the grading for damage is 

too conservative. 

Conclusions

Based on the analysis of test data generated from both small 

clear specimen testing and full-sized lumber tests, several 

conclusions can be drawn.

Clear Wood Properties

Based on the analysis of the calculated properties for the 

small clear bending test specimens cut from reclaimed 

Douglas-fir dimensional lumber—

1. Mean bending strength (MOR) was essentially the same 

as that of historical data.

2. Mean SG was essentially the same as that in historical 

data.

3. Mean MOE was about 10% greater than that in historical 

data.

4. Differences in MOR between groups of lumber from different locations can be explained by differences in SG. 

Based on these observations, we conclude that MOR and 

MOE of clear wood appear to be unaffected by aging and 

previous load history. 

Full-Size Lumber Properties

Based on the analysis of the calculated properties from 

the bending tests of reclaimed Douglas-fir dimensional 

lumber—

1. Mean bending strength (MOR) was about 25% lower 

than in-grade test data.

2. Mean stiffness (MOE) was about 10% higher than ingrade test data.

3. Existing size-effect equations are applicable for reclaimed lumber.

4. No geographical location effect was found for the four 

locations tested.

5. Nail holes become influential to MOR when they were 

closely spaced or if they had created further splitting, primarily when located at the high-stress tension edge. 

6. Shear failures were found to be relatively common in 

testing reclaimed lumber, though the bending strength of 

this lumber was higher than lumber failing at knots.
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

45

Table 36—Bending strength of No. 2 

lumber by grade determining defect 

(GDD), Douglas-fir and larch only 

No. 2 grade 

GDD N

MOR

(×103

 lb/in2)

a

Wane 5 6.74 

Bolt holes 0 0 

Other (skip, narrow, etc.) 26 6.22 

Damage 147 5.40 

Shake 31 5.21 

SOG 30 4.36 

Knots 173 4.07 

Splits 11 3.93 

Drying checks 2 2.78 

a

All full-size lumber data adjusted to 2 by 8 size. 

Table 35—Bending strength of Douglas-fir and larch by failure 

type 

All grades SS No. 2 

Failure type N

MOR

(×103

 lb/in2)

a N

MOR

(×103 lb/in2)

a N

MOR

(×103 lb/in2)

a

Compression 71 8.20 50 8.52 21 7.43 

Wood tension 152 6.75 94 7.06 58 6.25 

Shear 97 6.33 65 6.71 32 5.56 

Damage 115 6.00 79 6.27 36 5.42 

SOGb 126 5.60 70 6.15 56 4.92 

Knot 418 4.48 184 5.21 234 3.91 

a All full-size lumber data adjusted to 2 by 8 size. 

b Slope of grain. 

7. The frequency of lumber failures involving damage were 

less common than lumber with damage as the gradedetermining defect, suggesting that grading may be too 

conservative regarding damage. In addition, lumber failing at points of damage exhibited higher bending strength 

than lumber failing at knots. Additionally, the frequency 

of failures at points of damage was higher for SS than 

No. 2 grades.

Recommendations

The following recommendations are made with respect to 

the regrading and reuse of salvaged lumber:

1. Reclaimed lumber should be regraded before reuse. 

Grading rules, and possibly design guidelines, should 

formally recognize this material and provide guidance 

regarding appropriate reuse.

2. Any requirements for reuse should recognize the impracticality of identifying the exact species of each piece of 

2-by lumber salvaged and accommodate some degree of 

species mixing. 

3. Regular edge-nail holes should be placed in the compression zone, or away from the highest tension zone in 

design.

References

American Society for Testing and Materials. 2000 Annual 

book of standards (unless otherwise noted), Vol. 04.10, 

ASTM, West Conshohocken, PA:

D 198 - Standard Test Methods of Static Tests of Lumber 

in Structural Sizes 

D 1990 (2002) - Standard Practice for Establishing Allowable Properties for Visually-Graded Dimension Lumber from In-Grade Tests of Full-Size Specimens 

D 4761 - Standard Test Methods for Mechanical Properties and Wood-Base Structural Materials 

D 245 - Standard Practice for Establishing Structural 

Grades and Related Allowable Properties for Visually 

Graded Lumber 

D 143 (2007) - Standard Methods of Testing Small Clear 

Specimens of Timber 

D 2395 - Specific Gravity of Wood and Wood-Base 

Materials
46

Research Paper FPL–RP–650

D 2555 - Standard Test Methods for Establishing Clear 

Wood Strength Values

D 2915 - Standard Practice for Evaluating Allowable 

Properties for Grades of Structural Lumber 

D 4442 (2003) - Direct Moisture Content Measurement 

of Wood and Wood Base Materials

Bohannan, B. 1966. Effect of size on bending strength of 

wood members. Research Paper FPL–RP–56. Madison, WI: 

U.S. Forest Service, Forest Products Laboratory.

EPA. 1998. Characterization of building-related construction and demolition debris in the United States. Report No. 

EPA530R-98-010. Municipal and Industrial Solid Waste 

Division, Office of Solid Waste, U.S. Environmental Protection Agency, Washington, D.C. 

Falk, R.; Horne-Brine, P. 1999a. Knock on wood: real recycling opportunities are opening up. Resource Recycling. 

August: 42–46.

Falk, R.H.; Devisser, D.; Cook, S.; Stansbury, D. 1999b. Effect of damage on the grade yield of recycled lumber. Forest 

Products Journal. 49(7/8):71–79.

Falk, R.H.; Green, D.; Lantz, S.C. 1999c. Evaluation of 

lumber recycled from an industrial military building. Forest 

Products Journal. 49(5):49–55.

Falk, R.H.; Green, D. 1999d. Stress grading of recycled 

lumber and timber. In: 1999 structures congress: structural 

engineering in the 21 century; 1999 April 18-21; New 

Orleans, LA. Reston, VA: American Society of Civil Engineers. 650–653.

Falk, R.H.; Green, D.; Rammer, D.; Lantz, S.F. 2000. Engineering evaluation of 55-year-old timber columns recycled 

from an industrial military building. Forest Products Journal 

50(4):71–76.

Falk, R.H. 2002. Wood-framed building deconstruction: a 

source of lumber for construction? Feature Article, Forest 

Products Journal. 53(3):8–15.

Falk, R.H.; DeVisser, D.; Plume, G.R.; Fridley, K.J. 2003. 

Effect of drilled holes on the bending strength of large 

dimension Douglas-fir lumber. Forest Products Journal. 

53:55–60.

Falk, R.H.; Guy, G.B. 2005. Directory of wood-framed 

building deconstruction and reused wood building materials companies. General Technical Report FPL–GTR–150. 

Madison, WI: U.S. Forest Service, Forest Products Laboratory. 95 p.

Forest Products Laboratory. 1999. Wood Handbook: Wood 

as an Engineering Material. General Tech. Report FPL–

GTR–113. Madison, WI: U.S. Forest Service, Forest Products Laboratory. 463 p.

Fridley, K.J.; Mitchell, J.B.; Hunt, M.O.; Senft, J.F. 1996. 

Effect of 85 years of service on mechanical properties of 

timber roof members. Part 1. Experimental observations. 

Forest Products Journal. 46(5):72–78.

Green, D.W.; Falk, R.H.; Lantz, S.F. 2001. Effect of heart 

checks on flexural properties of reclaimed 6 by 8 Douglasfir timbers. Forest Products Journal 51(7/8): 82–88.

Green, D.W.; Evans, J.W. 1989. The specific gravity of 

visually graded lumber. U.S. Department of Commerce. 

National Technical Information Service, Springfield, VA. 

Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 105 p.

Green, D.W.; Evans, J.W. 1988. Mechanical properties of 

visually graded lumber: Volumes 1–8. U.S. Department of 

Commerce. National Technical Information Service, Springfield, VA PB–88–159–371. 

Howard, J.L. 2001. U.S. Timber production, trade consumption, and price statistics 1965 to 1999. Res. Pap. 

FPL–RP–595. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory. 90 p.

Lanius, R.M.; Tichy, R.; Bulliet, W.M. 1981. Strength 

of old joists. Journal of Structural Engineering, ASCE. 

107(12):2349–2364.

Maul, D.G. 2004. Bending strength of reclaimed dimensional lumber, a thesis submitted in partial fulfillment of the 

requirements for the degree of Master of Science (Civil Engineering), University of Wisconsin–Madison.

NDS. 2001. National Design Specification for Wood. Washington, DC: American Forest and Paper Association. 

Rammer, D.R. 1999. Evaluation of recycled timber members. In: Bank, Lawrence C., ed. Materials and construction—Exploring the connection. Proceedings, 5th ASCE 

Materials Engineering Congress; 1999 May 10–12; Cincinnati, OH. Reston, VA: American Society of Civil Engineers: 

46–51.

West Coast Lumber Inspection Bureau. 2000. Standard No. 

17. Grading Rules for West Coast Lumber. Portland, OR: 

West Coast Lumber Inspection Bureau.
Engineering Properties of Douglas-fir Lumber Reclaimed from Deconstructed Buildings

47

1

 

General Information Setup 

 

Size: 2x8 

Species: Douglas-fir 

Location: Washington 

 

 

EML #: 20005_B5 Nail Holes 

Test #: Orientation Spacing 

Date: Nail Holes: Up Down None 

Specimen #: 

 Worst Flaw 

 Orientation Type 

Dimensions Visual Up Down None 

 Failure Causing Up Down None 

b = in. 

h = in. 

L = in. Failure Information 

Sag = in. 

 Failure Code: 

Third Point Bending Macro Output 

 Cross-section 

Time = seconds 

Pmax= kips 

MOR = lb/in.2 

r

2

= 

# points = 

SEE = lb/in.2 

MOE = ksi*103 

 

 Board Schematic 

Splits 

 

Edge: None Some Severe 

Face : None Some Severe Opposite 

 Face 

 

Moisture Meter % 

 

 

Comments 

 

c

L

= = =

P P

1

20" MOD 

Appendix—Reclaimed Lumber Test Worksheet