Condition Assessment of 

Roof Trusses of Quincy 

Mine Blacksmith Shop in 

Keweenaw National 

Historical Park

Carol A. Clausen 

Robert J. Ross 

John W. Forsman 

Joseph D. Balachowski 

United States

Department of 

Agriculture 

Forest Service 

Forest 

Products 

Laboratory 

Research 

Note 

FPL−RN−0281 
Abstract 

Condition assessment is an important first step in the restoration of any historic structure. Immunodiagnosis of wood 

decay fungi, nondestructive evaluation (NDE) stress wave 

mapping, and compression perpendicular to grain were used 

to evaluate white pine roof truss timbers from the Blacksmith Shop of the Quincy Mining Company in Keweenaw 

National Historical Park. Immunodiagnosis indicated that 

areas in the timber had been exposed to decay fungi. Stress 

wave NDE mapping located voids in the timbers tested. 

Compression perpendicular to the grain correlated with NDE 

findings. 

Keywords: Immunodiagnostic, stress wave NDE, 

compression testing 

August 2001 

Clausen, Carol A.; Ross, Robert J.; Forsman, John W.; Balachowski, Joseph 

D. 2001. Condition assessment of roof trusses of Quincy Mine Blacksmith 

Shop in Keweenaw National Historical Park. Res. Pap. FPL-RN-0281. 

Madison, WI: U.S. Department of Agriculture, Forest Service, Forest 

Products Laboratory. 4 p. 

A limited number of free copies of this publication are available to the 

public from the Forest Products Laboratory, One Gifford Pinchot Drive, 

Madison, WI 53705–2398. Laboratory publications are sent to hundreds 

of libraries in the United States and elsewhere. 

The Forest Products Laboratory is maintained in cooperation with the 

University of Wisconsin. 

The use of trade or firm names is for information only and does not imply 

endorsement by the U.S. Department of Agriculture of any product or 

service. 

The United States Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national 

origin, sex, religion, age, disability, political beliefs, sexual orientation, or 

marital or familial status. (Not all prohibited bases apply to all programs.) 

Persons with disabilities who require alternative means for communication 

of program information (Braille, large print, audiotape, etc.) should contact 

the USDA’s TARGET Center at (202) 720–2600 (voice and TDD). To file a 

complaint of discrimination, write USDA, Director, Office of Civil Rights, 

Room 326-W, Whitten Building, 1400 Independence Avenue, SW, 

Washington, DC 20250–9410, or call (202) 720–5964 (voice and TDD). 

USDA is an equal opportunity provider and employer. 
Condition Assessment of Roof Trusses 

of Quincy Mine Blacksmith Shop in 

Keweenaw National Historical Park 

Carol A. Clausen, Microbiologist

Robert J. Ross, Supervisory Research General Engineer

Forest Products Laboratory, Madison, Wisconsin 

John W. Forsman, Assistant Research Scientist 

School of Forestry and Wood Products 

Michigan Technological University, Houghton, Michigan

Joseph D. Balachowski, Architect 

U.S. Department of Interior, National Park Service, Washington, DC

Introduction 

The Quincy Mining Company was part of the copper mining 

boom on Michigan’s Keweenaw Peninsula resulting from 

the discovery of large masses of native copper in the mid1840s. By 1930, Quincy was the deepest mine in the Western Hemisphere, going down as far as 9,200 ft (2,804 m) 

below the surface. By the time Quincy closed in 1945, it had 

produced 848 million pounds (384,646 metric tons) of copper. The Mine Hoist and Number Two Shafthouse have been 

preserved by the Quincy Mine Hoist Association and are 

open for public tours. The preservation of this 100-year-old 

mine site includes the Quincy Mining Company Blacksmith 

and Machine shops, which are part of the Keweenaw National Historical Park. Both structures are slated for renovation in conjunction with the National Park Service. 

Condition assessment of the heavy timber roof trusses of the 

Blacksmith Shop was an important first step in the restoration of this structure. In addition to visual inspection, the 

condition of representative timbers exposed to the elements 

since the removal of the roof was assessed by compression 

strength perpendicular to grain, stress wave transmission, 

and immunodiagnosis of wood decay fungi. Recognition 

of early decay is important for the inspection of wood in 

service. 

Early decay is difficult to recognize because it is visually 

subtle and often occurs on the interior of a timber or below 

ground. Visually, macroscopic changes in color or texture 

provide presumptive evidence of early decay; only the 

physical presence of fungi is considered definitive. Microscopic examination that reveals hyphae with clamp connections provides definitive evidence of early decay (Zabel and 

Morrell 1992). Nonvisual methods of identifying early decay 

include culturing the fungus from the infected wood and 

various physical tests, such as those that indicate a change in 

strength properties, acoustic changes, and electrical changes. 

Wood decay caused by brown-rot decay fungi has typically 

been described as having four stages: incipient, early, intermediate, and advanced. Incipient decay occurs when decay 

fungi initiate colonization and release enzymes; there is no 

visible evidence of damage. During early decay, slight 

changes in color or texture occur, but decay is not obvious. 

Intermediate decay includes obvious changes in color and 

texture, although the wood structure still appears intact. 

Advanced decay is obvious because the wood structure is 

affected; the wood turns brown and crumbly with a cubical 

appearance. 

Inspection methods are currently a combination of tests 

for physical detection of decay (for example, sounding, 

boring), mechanical detection (compression test, splinter 

test), electrical detection (moisture meter, x-ray), or acoustic 

detection (acoustic emissions, stress wave time). Laboratory 

detection methods, such as culturing, microscopy, and serological tests, though definitive for early stages of decay and 

valuable to the inspection process, have historically not lent 

themselves to field use. Because hemicelluloses are rapidly 

removed by brown-rot fungi during incipient decay, the 

immunodiagnostic wood decay test was designed to target 

a hemicellulase enzyme, specifically endo-1,4-ß-xylanase 

(Clausen and Green 1996). Anti-xylanase antibodies detect 

minute quantities of xylanase, which indicates the presence 

of incipient decay. Work to maximum load, toughness, and 

impact bending are also reported to be sensitive mechanical 

methods for detecting early decay (Wilcox 1978), and stress 

wave mapping has been used successfully to locate deteriorated regions in timbers (Ross and others 1997b). The 
2 

relationship between stress wave transmission and compressive strength in biodeteriorated wood has been demonstrated 

in Southern Pine (Ross and others 1997a). 

The objective of this study was to compare mechanical 

(compression perpendicular to grain), acoustic (stress wave 

analysis), and laboratory fungal decay (immunodiagnostic) 

methods for detecting decay in samples from two eastern 

white pine timber trusses of the Quincy Mine Blacksmith 

Shop. 

Materials and Methods 

Sampling 

Two eastern white pine (Pinus strobus var. strobus L.) 

specimens measuring 12 in. by 12 in. by 8 ft (30.5 cm by 

30.5 cm by 2.4 m) and 7 in. by 9 in. by 10 ft (17.8 cm by 

22.9 cm by 3 m) were removed from the site for testing. The 

12-in. (30.5-cm) square beam was solid on one end, with a 

crack near the center of the span. Signs of decay were visible; the opposite end of the beam was hollow. The 7- by 

9-in. (17.8- by 22.9-cm) beam was solid on both ends. 

Initially, decay mapping was conducted on each beam using 

stress wave nondestructive evaluation (NDE). Both beams 

were sawn on all four sides to remove up to 1⁄4 in. (0.64 cm) 

of the outer layer of weathered wood. Weathered wood may 

harbor contaminants that could result in false positive reactions in the immunodiagnostic wood decay test. Cross sections of each beam were cut at 12-in. (30.5-cm) intervals 

to test for compression strength perpendicular to grain. 

Stress Wave NDE 

Decay mapping consisted of recording a series of stress 

wave measurements taken at 6-in. (15-cm) intervals over the 

length of the span and at multiple sites on two faces of the 

beam. Readings on each face were taken at approximately 

2-in. (5-cm) intervals to produce a grid of readings, as 

indicated in Figure 1a. Readings exceeding 600 μs were 

designated as representative of decay. 

Immunodiagnosis 

Samples were taken at 6-in. (152-cm) intervals along each 

specimen by drilling to the center of the beam with a 0.25-in. 

(0.64-cm) drill bit and collecting sawdust for testing. Fifty 

milligrams of each sawdust sample was extracted in 2 mL 

water plus 0.01% Triton X–100 (Sigma, St. Louis, MO) for 

2 h at 77o

F (25oC) with agitation. Following extraction, each 

fluid was tested with the immunodiagnostic wood decay test 

(Clausen 1994, Clausen and Green 1997), with results recorded as positive (+) or negative (–) for decay on the sampling diagram (Fig. 1). 

Compression Perpendicular to Grain 

(ASTM D143) 

Compression perpendicular-to-grain tests were conducted on 

samples taken at 12-in. (30.5-cm) intervals and tested in 

accordance with ASTM D143–94 (ASTM 1998). Sampling 

sites and results are indicated on the beam diagram (Fig. 1a). 

Condition: Solid

Immunodiagnosis

1 2 3 4 5 6 7 8 9 10

Foot increments

+ + + + - + + - - - + + + - - - - - - - -

Crack

Condition: Solid

1 2 3 4 5 6 7 8

Immunodiagnosis

Compression strength (lb/in2)

Foot increments

+ + + + + - - - - + + + + Hollow

202 188 221 140 67 ND ND

(a)

(b)

Figure 1—Results of tests on eastern white pine roof trusses: (a) 12-in. by 12-in. by 8-ft (30.5-cm by 30.5-cm by 2.4-m) 

truss; shaded area indicates deterioration detected by stress wave mapping; ND designates areas not sampled for 

compression strength because of advanced visible decay; (b) results of immunodiagnosis of 7 in. by 9-in. by 10-ft 

(17.8-cm by 22.9-cm by 3-m) roof truss; no deterioration or voids were detected by NDE mapping. 
3 

Results and Discussion 

Eastern white pine roof trusses from the Blacksmith Shop of 

the Quincy Mining Company were evaluated for deterioration as part of the restoration of this historic structure. The 

12-in. by 12-in. by 8-ft (30.5-cm by 30.5-cm by 2.4-m) 

timber specimen was solid on one end, with a crack forming 

near the center of the span; signs of decay were visible along 

the span, and the other end of the specimen was hollowed by 

decay. Assessing this timber permitted evaluation of each 

test method for sensitivity to detect incipient decay along the 

length of the span as decay visibly progressed. Positive 

reactions to the immunodiagnostic wood decay tests were 

observed in samples up to 2.5 ft (76 cm) from both ends of 

the specimen. In the early stages of decay, rapid strength 

losses associated with brown-rot are due to the damaging 

effect of extracellular enzymes that diffuse away from the 

hyphae creating damage beyond the colonized cells, which 

occurs during incipient decay. Immunodiagnostic tests specifically detect the presence of brown-rot fungal enzymes 

during incipient decay, prior to strength or weight loss, as 

reported in this study (Clausen and others 1991, Clausen 

and Ferge 1995, Clausen 1997). 

Stress wave readings on the 12-in. by 12-in. by 8-ft (30.5-cm 

by 30.5-cm by 2.4-m) timber specimen indicated decay 

beginning near the deep crack in the center of the span and 

progressing to the hollowed end of the specimen. Stress 

wave NDE measures the speed (transmission time) at which 

stress waves travel through a wood member (Ross and others

1994, Ross and Pellerin 1994). NDE locates voids in wood 

caused by insects, decay fungi, or other physical defects. It 

does not specifically distinguish between active decay, 

voids, ring shakes, or other defects (Wilcox 1978). In defectfree timbers, research has shown that stress wave signals are 

slowed significantly in areas containing deterioration compared to sound wood, and this method has been used successfully to locate deteriorated regions in timbers (Ross and 

others 1997b). In the 12-in. by 12-in. (30.5-cm by 30.5-cm) 

specimen, decay was mapped and differentiated from sound 

wood by NDE (Fig. 1a). 

Of the many strength properties used to measure the effects 

of decay on wood, work to maximum load, toughness, and 

impact bending are reported to be the most sensitive methods 

to detect early decay (Wilcox 1978). For the 12-in. by 12-in. 

by 8-ft (30.5-cm by 30.5-cm by 2.4-m) timber, tests on 

compression perpendicular-to-grain indicated a decrease in 

compressive strength in the same location as did NDE. The 

relationship between stress wave transmission and compressive strength in biodeteriorated wood was previously demonstrated in southern pine (Ross and others 1997a). NDE 

and compressive strength compared favorably as methods to 

predict the residual strength of a specimen. 

The 7 in. by 9-in. by 10-ft (17.8-cm by 22.9-cm by 3-m) 

specimen was solid throughout, but it showed three distinct 

areas of positive reaction to the immunodiagnostic wood 

decay test along the length of the span, which is indicative of 

incipient decay (Fig. 1b). Except for a single reading at 0 in., 

no stress wave reading exceeded 600 μs for this timber. 

Deteriorated pine yields readings in excess of 600 μs; 

therefore, compression tests were not conducted. 

Conclusions 

In this study, the immunodiagnostic wood decay test diagnosed areas of incipient fungal colonization (that is, prior to 

strength loss) in each test specimen. Compressive strength 

and stress wave NDE mapping showed areas of early decay; 

these results were comparable. NDE was a more exacting 

method for pinpointing the boundary of a deteriorated region, which is desirable when salvaging specimens from an 

historic structure. These results represent a small pilot study. 

Future studies are needed to evaluate a large sampling of 

specimens. 

References

ASTM. 1998. Standard methods of testing small clear 

specimens of timber. In: Annual Book of ASTM Standards, 

ASTM D 143–94. Philadelphia, PA: American Society for 

Testing and Materials. Vol. 4.10: 22–52. 

Clausen, C.A. 1994. Dyed particle capture immunoassay 

for detection of incipient brown-rot decay. Journal of 

Immunoassay 15: 305–316. 

Clausen, C.A. 1997. Immunological detection of wood 

decay fungi. An overview of techniques developed from 

1986–present. International Biodeterioration and Biodegradation. 39(2–3):133–143. 

Clausen, C.A.; Ferge, L. 1995. Dimensional lumber model 

demonstrates the sensitivity of the particle capture immunoassay in early detection of brown-rot fungi. International 

Group on Wood Preservation. Doc. IRG/WP/95–20058. 

Clausen, C.A.; Green III, F. 1996. Method and apparatus 

for immunological diagnosis of fungal decay in wood. 

U.S. Patent 5,563,040. 

Clausen, C.A.; Green III, F.; Highley, T.L. 1991. Early 

detection of brown-rot decay in southern yellow pine using 

immunodiagnostic procedures. Wood Science Technology.

26: 1–8. 

Ross, R.J.; Pellerin, R.F. 1994. Nondestructive testing for 

assessing wood members in structures. A review. Gen. Tech. 

Rep. FPL–GTR–70. Madison, WI: U.S. Department of 

Agriculture, Forest Service, Forest Products Laboratory. 

40 p. 
4 

Ross, R.J.; De Groot, R.C.; Nelson, W.J. 1994. Technique 

for nondestructive evaluation of biologically degraded wood. 

Experimental Techniques. 18(5): 29–32. 

Ross, R.J.; De Groot, R.C.; Nelson, W.J.; Lebow, P.K.

1997a. The relationship between stress wave transmission 

characteristics and the compressive strength of biologically 

degraded wood. Forest Products Journal. 47(5): 89–93. 

Ross, R.J.; Soltis, L.A.; Otton, P. 1997b. Assessing wood 

members in the USS Constitution using non-destructive 

evaluation methods. Journal of Preservation and Technology. 24(2): 21–25. 

Wilcox, W.W. 1978. Review of literature on the effects of 

early stages of decay on wood strength. Wood and Fiber 

9(4): 252–257. 

Zabel, R.A.; Morrell, J.J. 1992. In: Wood microbiology: 

decay and its prevention. San Diego, CA: Academic Press.