Forest Products

Commercial Species

Alaska (Yellow) Cedar (Chamaecyparis nootkatensis) & Western Red Cedar (Thuja plicata)

Western Red Cedar Alaska Cedar

Written By: Eugene E. Wheeler, Retired USDA Forest Service Program Manager for Cooperative Forestry Programs, (Alaska) Region 10. Currently a consultant for Idaho Panhandle Forestry.

Introduction. This booklet contains a brief discussion of the botanical and wood structural characteristics, forest associations, and some of the commercial uses of Alaska yellow cedar and western Red Cedar in Alaska.

Both species are coastal species and have decay resistant. However, their characteristics diverge from there. These differences, as well as similarities, will be pointed out. This booklet is nontechnical and provides an introduction to the two species, and the Alaska forest environment in which they grow.

The Climate. The habitat of the two cedars in Alaska is an extension of the rain belt forests of Oregon and Washington. This rain belt extends along the Alaska coast to Kodiak Island. The forest environment of coastal Alaska is wet to extremely wet with moderate temperatures. Precipitation ranges from 60 to over 200 inches (152 to 508 centimeters) annually. Summer temperatures are from 47°-70°F (7°-21°C), while winter temperatures can drop below -20°F (-29°C). The growing season is moderately short (130-160 frost free days), with long periods of daylight (18-21 hours) which provide optimum solar energy for maximum tree growth.

Both cedars are slow growing and are found most often on the poorer soils. Best growth in natural stands is found on very wet sites in the fog belt along the coastal plain. This is probably because the Sitka spruce or hemlock cannot compete with the cedars on these sites.

The Forest. The coastal forests of Alaska occur from shoreline to elevations of 2,000 to 3,000 (610 to 914 meters) and from the southern end of Alaska to Kodiak Island. Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) dominate the forests of coastal Alaska, especially on the deeper, well-drained sites of the river flood plains and lower slopes. Mountain hemlock (Tsuga mertensiana) dominates the upper slopes, extending to elevations above all other species (up to 3,500 feet or 1,067 meters). The two cedars are found in association with Sitka spruce and western hemlock on the lower slopes and flood plains and with mountain hemlock on the upper slopes. Western red cedar attains its best growth below elevations of 500 feet (152 meters), while Alaska cedar reaches its best development between 500 and 1,200 feet (152 and 366 meters). Western red cedar is not found beyond Fredrick Sound, whereas, Alaska cedar extends as far westward as Prince William Sound. The two cedars seldom occur as pure stands, except on very wet soils where competing species cannot survive. There are about 13.25 million acres of forest land in coastal Alaska, including all of the islands which make up a significant portion of the acreage. Sitka spruce and western hemlock types account for 96% of the forest area. The balance is comprised mostly of mountain hemlock and an insignificant acreage of cedar types.

Wood Properties. Because there are many differences in wood properties, the two species will be discussed separately.

Western red cedar wood has a distinctive odor characteristic of cedars. Summerwood is distinctly narrower, darker, and harder than springwood. The wood has a fine, moderately even texture. It is light in weight, weak in bending, moderately limber and soft, low in shock resistance, and has a very small shrinkage when seasoned. The wood is straight grained. Red cedar is moderately easy to kiln dry, stays in place well, very easy to work, moderately easy to glue, and takes paint and stains satisfactorily. The wood is resistant to termite attack. Red cedar wood works easily resulting in a good finish but is somewhat brittle and may splinter. Chip bruises may occur unless the waste disposal system keeps the working surfaces clean. The soft springwood may be depressed by dull tools only to rise later creating ridges on the surface.

Alaska yellow cedar heartwood is a bright clear yellow, while the sapwood is lighter in color. The wood contains a volatile oil which gives it a distinctive odor and may add a gloss to worked surfaces. It has a fine, even texture and is relatively straight-grained. The wood is heavy in weight for a softwood, moderately weak in bending and compression, moderately stiff, moderately hard, moderately high in shock resistance, and has a small shrinkage when seasoned. Alaska cedar is very easy to kiln dry, stays in place well, is very easy to work, but has a low nail-holding capacity. It is easy to glue, may not take paint or stain well if not properly dried, and works very easily without the problem of brittleness or soft grain that red cedar has. The wood has unusually high static and impact bending strength for a softwood species.

Seasoning. The cedars air dry slowly in the coastal area and if air dried, the best site and quality control must be used. Both species are easily kiln dried. However, lumber sawn from wet red cedar logs such as "sinkers" must be air dried to a 50% or less moisture content prior to kiln drying. Otherwise, the wood cells may collapse and honeycomb. Drying schedules for red cedar vary from 50 hours to 22 days at temperatures of 120°-140°F (49°-60°C) with wet-bulb depressions of 5°-10°F (3°-6°C).

Drying schedules for Alaska cedar vary from 72 hours to 7 days at temperatures of 130°-160°F (54°-71°C) with wet-bulb depressions of 2°7°F (1°-4°C).

Other Properties. The following wood properties are averages derived from previous U.S.F.S. reports concerning the two cedar species. The figures are averages derived from tests on samples of woods harvested in Alaska. Variables from other known data may be caused by growing and handling conditions.

Weights

A. Solid Wood - Average weight in pounds per cubic foot (kilograms per cubic meter).

Green (34% moisture content)

26 lbs./cu.ft
(416 kg./cu. m.)

Seasoned (12% moisture content)

23 lbs./cu.ft.
(368 kg./cu. m.)

Alaska Cedar

Green (34% moisture content) 37 lbs./cu.ft
(593 kg./cu. m.)
Seasoned (12% moisture content) 33 lbs./cu.ft.
(529 kg./cu. m.)

B. Logs (Approximated)

1. Average weight per log in pounds. (Kilograms)

Western Red Cedar
Sealing Diameter

Log Lengths

8 feet (2.4 meters) 12 feet (3.7 meters)
 8" (20.3 cm.) 104 156
12" (30.5 cm.) 234 312
16" (40.6 cm.) 351 520
20" (50.8 cm.) 520 793
16 feet (4.9 meters) 20 feet (6.1 meters)
 8" (20.3 cm.) 208 260
12" (30.5 cm.) 416 507
16" (40.6 cm.) 689 871
20" (50.8 cm.) 1,040 1,313
 
 
Alaska Cedar
Sealing Diameter

Log Lengths

8 feet (2.4 meters) 12 feet (3.7 meters)
 8" (20.3 cm.) 184 (  67) 222 (101)
12" (30.5 cm.) 333 (151) 444 (201)
16" (40.6 cm.) 500 (227) 740 (336)
20" (50.8 cm.) 740 (336) 1,129 (512)
16 feet (4.9 meters) 20 feet (6.1 meters)
 8" (20.3 cm.) 296 (134) 370 (168)
12" (30.5 cm.) 592 (269) 722 (327)
16" (40.6 cm.) 981 (445) 1,240 (562)
20" (50.8 cm.) 1,480 (671) 1,869 (848)

2. Average log weight per MBF using Scribner Decimal "C" Log Rule Scale.

Western Red Cedar
 Scaling Diameter Weight Per MBF
8" (20.3 cm.) 6,933 lbs. (3,145 kg.)
12" (30.5 cm.) 5,200 lbs. (2,359 kg.)
16" (40.6 cm.) 4,306 lbs. (1,953 kg.)
20" (50.8 cm.) 3,714 lbs. (1,685 kg.)
24" (60.9 cm.) 3,705 lbs. (1,681 kg.)
30" (71.0 cm.) 2,408 lbs. (1,546 kg.)
 
Alaska Cedar
 Scaling Diameter Weight Per MBF
8" (20.3 cm.) 9,867 lbs. (4,475 kg.)
12" (30.5 cm.) 7,400 lbs. (3,357 kg.)
16" (40.6 cm.) 6,131 lbs. (2,781 kg.)
20" (50.8 cm.) 5,286 lbs. (2,396 kg.)
24" (60.9 cm.) 5,273 lbs. (2,392 kg.)
30" (71.0 cm.) 4,850 lbs. (2,200 kg.)

C. Lumber - Average weight in pounds (kilograms) per MBF.

1. Rough Lumber

 
Red Cedar Alaska Cedar
Green lbs. 2,710 3,850
kgs. 1,229 1,746
Seasoned lbs. 2,400 3,020
kgs. 1,089 1,370

2. Surfaced Lumber

Red Cedar Alaska Cedar
Green lbs. 1,630 2,310
kgs. 739 1,048
Seasoned lbs. 1,440 1,810
kgs. 653 821

II. Specific Gravity

 
Red Cedar Alaska Cedar
Green 0.31 0.44
Seasoned (12% MC) 0.33 0.47

III. Shrinkage - Percent from green to seasoned, based on original
green dimensions.

Red Cedar Alaska Cedar
(Tangential)* 4.6 7.7
Thickness (Radial)* 2.2 4.2
Volume 7.0 11.4

* Flat-grain board. Reverse for quarter-sawn or edge grain board.

IV. Basic Strength Values and Mechanical Properties of Red Cedar and Alaska Cedar. (Strength properties of white spruce increase as the wood is dried out.)

 
Green Seasoned
WRC AC WRC AC
A. Hardness - Load required to embed a 0.444 inch (1.1 cm.) ball to 1/2 its diameter.
End grain (lbs.) 430 570 720 950
(kg.) 195 259 327 431
Side grain (lbs.) 290 500 390 690
(kg.) 132 227 177 313
B. Static Bending
Fiber Stress at Elastic Limit (psi)* 3,000 4,100 5,700 8,200
(ksc)** 211 288 401 577
Modulus of Rupture
Fiber Stress at Elastic Limit (psi) 4,900 6,900 8,000 13,200
(ksc) 345 485 562 928
Modulus of Elasticity
(psi) 850 1,400 1,040 1,700
(ksc) 60 100 73 120
Work to Elastic Limit
(in.-lb. per cu. in.) .62 .77 1.80 2.12
(cm.-kg. per cu. in.) .007 .008 .02 .023
Work to Maximum Load
(in.-lb. per cu. in.) 4.9 8.8 5.6 13.0
(cm.-kg. per cu. in.) .053 .096 .061 .142
C. Impact Bending - Height of drop causing complete failure - 50 lb. (22.7 kg.)  hammer.          
(inches)
17 27 19 29
(centimeters)
43 69 48 74
D. Compression Parallel to the Grain Fiber Stress at Elastic Limit          
(psi) 2,130 2,800 4,060 6,100
(ksc) 150 197 285 429
Maximum Crushing Strength          
(psi) 2,560 3,330 4,990 7,520
(ksc) 150 234 351 529
E. Shearing Strength          
(Parallel to Grain) (psi) 690 880 870 1,380
(ksc) 49 62 61 97
F. Tension          
(Perpendicular to the Grain) (psi) 280 430 300 370
(ksc) 20 30 21 26
G. Compression
(Perpendicular to grain, fiber stress at elastic limit) (psi) 380 470 700 910
(ksc) 27 33 49 64

* Pounds per square inch - psi

** Kilograms per square centimeter - ksc

Uses of the Trees. Both Alaska cedar and western red cedar are being exported to Japan as round logs. An exception to the U.S.F.S. primary manufacture rule has been granted to timber purchasers of national forest timber, making the cedars a prime export product.

The two cedars are highly valued for boat construction when wood is the chosen construction material. Both cedars are highly durable and resist attack by the various insects which are encountered in the marine environment. The cedars are used extensively for poles, piling, light construction, fence posts, lining for boxes and closets, and as stock for specialty products such as toys. Red cedar is the most widely used wood for shingles and shakes. Alaska cedar is highly valued for window frames, doors and other fine finish purposes for which wood is the most desirable material.