Thuja plicata

 

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Family: Cupressaceae

 

 

 

 

 

 

 

 

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Western Redcedar

 

 

 

The genus Thuja contains about 6 species world-wide native to North America [2] and Asia [4]. The word thuja comes from the Greek thuia, an aromatic wood (probably a juniper). The word plicata is derived from plicate (folded into plaits) most likely from the flat, folded appearance of the scale-like leaves.

Other Common Names: Albero della vita di Lobb, amerikanskt livstrad, amerikanskt livstrad, arbol de la vida, arborvitae, British Colombia red cedar, British Columbia cedar, California cedar, canoe cedar, cedar, cedro rojo del Pacifico, cedro rosso del pacifico, columinar giant arborvitae, giant arbor, giant arborvitae, giant cedar, giant thuja, gigantic cedar, gigantic red cedar, grand arbre de vie, Idaho cedar, jatte-tuja, Lobb's arborvitae, northwestern red cedar, Oregon cedar, pacific arbor, Pacific arborvitae, Pacific red cedar, red cedar, red cedar of the west, red cedar pine, reuzen-thuja, reuzenthuja, riesen-lebensbaum, riesenlebensbaum, riesenthuja, shinglewood, thuja geant, thuya de Lobb, thuya geant, thuya oriental, tuia gigantesca, Washington cedar, Washington red cedar, Westamerikaanse levensboom, western arborvitae, western cedar, western redcedar, western red redcedar.

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Distribution: Western redcedar (Thuja plicata) grows in the Pacific Northwest and along the Pacific coast to Alaska. Western redcedar lumber is produced principally in Washington, followed by Oregon, Idaho, and Montana. The tree has been planted in Great Britain and New Zealand.

The Tree: Western redcedar trees reach heights of 200 feet with diameters of 16 feet. The trunk of older trees is buttressed, fluted and quite tapered.

General Wood Characteristics: The heartwood of western redcedar is reddish or pinkish brown to dull brown and the sapwood nearly white. The sapwood is narrow, often not over 1 inch in width. The wood is generally straight grained and has a uniform but rather coarse texture. It has very small shrinkage. This species is light in weight, moderately soft, low in strength when used as a beam or posts, and low in shock resistance. Its heartwood very resistant to decay.

 

 

Mechanical Properties (2-inch standard)

 

 

 

 

Compression

 

 

 

 

Specific

gravity

MOE

x106 lbf/in2

MOR

lbf/in2

Parallel

lbf/in2

Perpendicular

lbf/in2

WMLa

in-lbf/in3

Hardness

lbf

Shear

lbf/in2

Green

0.31

0.94

5200

2770

240

5.0

260

770

Dry

0.34

1.11

7500

4560

460

5.8

350

990

aWML = Work to maximum load.

Reference (59).

 

Drying and Shrinkage

Type of shrinkage

Percentage of shrinkage
(green to final moisture content)

0% MC

6% MC

20% MC

Tangential

5.0

4.0

1.7

Radial

2.4

1.9

0.8

Volumetric

6.8

5.4

2.3

References: (56, 192).

Kiln Drying Schedulesa

 

Conventional temperature/moisture content-controlled schedulesa


Condition

4/4, 5/4
stock

6/4 stock

8/4
stock

10/4
stock

12/4
stock

British schedule
4/4 stock

Light Weight

T10-B5

NA

T10-B3

T7-A2

T7-A2

J

Heavy Weight

T5-F4

NA

T5-F3

NA

NA

NA

aReference (28, 185).

 

Conventional temperature/time-controlled schedulesa

 

Lower grades

Upper grades


Condition

4/4, 5/4 stock

6/4 stock

8/4 stock

4/4, 5/4 stock

6/4 stock

8/4 stock

12/4, 16/4 stock

Standard

290

290

289

290

290

296

NA

aReferences (28, 185) .

Working Properties: The timber works well with both hand tools and machine operations. It may splinter when worked on the end grain (mortising, etc.). It is subject to compression during planing and molding. It nails and screws well and takes both stains and paint satisfactorily (5).

Durability: Western redcedar is rated as resistant to very resistant to heartwood decay (14). It is not immune to attack by termites and furniture beetles (5).

Preservation: It is resistant to preservative treatment.

Uses: Western redcedar is used principally for shingles, lumber, poles, posts, and piles.

The lumber is used for exterior siding, interior finish, greenhouse construction, ship and boat building, boxes and crates, sash, doors, and millwork.

Toxicity: May cause bronchial asthma and/or contact dermatitis (4,9&17).

 

Additional Reading and References Cited (in parentheses)

1. Anon. Thuja plicata, western red cedar, No. 4. Wood. 1936; 1(4):176-177.

2. Boone, R. S.; Kozlik, C. J.; Bois, P. J., and Wengert, E. M. Dry kiln schedules for commercial woods - temperate and tropical. Madison, WI: USDA Forest Service, FPL-GTR-57; 1988.

3. Gardner, J. A. F. The chemistry and utilization of western red cedar. Ottawa, Canada: Canada Department of Forestry, Forest Products Research Branch, No. 1023.; 1963.

4. Hausen, B. M. Woods injurious to human health. A manual. New York, NY: Walter de Gruyter; 1981.

5. Henderson, F. Y. A handbook of softwoods. London: HMSO; 1977.

6. Hyam, R. and Pankhurst, R. Plant and their names. A concise dictionary. Oxford, UK: Oxford University Press; 1995.

7. Lowery, D. P. Western Larch, an American wood. Washington, DC, USA: USDA Forest Service, FS-243; 1984.

8. Minore, D. Thuja plicata Donn ex D. Don, western redcedar. in: Burns, R. M. and Honkala, B. H., technical coordinators. Silvics of North America. Volume 1, Conifers. Washington, DC: USDA Forest Service, Ag. Handbook 654; 1990.

9. Mitchell, J. and Rook, A. Botanical dermatology: plants and plant products injurious to the skin. Vancouver, BC: Greenglass Ltd.; 1979.

10. PFI. Lamintaed western red cedar roof decking. Lewiston, ID, USA: Potlach Forests, Inc., AIA File No. 19-B-3; 1959.

11. Record, S. J. and Hess R. W. Timbers of the new world. New Haven, CT: Yale University Press; 1943.

12. Simpson, W. T. Dry kiln operator's manual. Madison, WI: USDA Forest Service, FPL Ag. Handbook No. 188; 1991.

13. Summitt, R. and Sliker, A. CRC handbook of materials science. Vol. 4. Boca Raton, FL: CRC Press, Inc.; 1980.

14. USDA. Wood handbook: wood as an engineering material. Madison, WI: USDA Forest Service, FPL Ag. Handbook No. 72; 1974.

15. WCLA. Wetsern red cedar lumber, grades and uses. Portland, OR, USA: West Coast Lumberman's Association, AIA File, No. 19-A-1; ?

16. Wentling, J. P. Western red cedar, the ideal pole. Minneapolis: Western Red and Northern White Cedar Association; 1938.

17. Woods, B. and Calnan, C. D. Toxic woods. British Journal of Dermatology. 1976; 95(13):1-97.