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Western Red Cedar
Characteristics & Technical Data
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Western Red Cedar (Thuja Plicata) is renowned for its natural beauty and outstanding physical properties that make it one of the world’s most unique softwood species. This exceptionally beautiful wood has natural colouring in mellow ambers, reddish cinnamons and rich sienna browns. Its warm colouring is complemented by a uniform, fine-grained texture with a satin lustre.Western Red Cedar formed an integral part of the spiritual and practical life of the Northwest Coast Indians. The tree was used for constructing the walls and roofs of lodges, totem poles, canoes and utensils while the bark was used for weaving baskets, mats, rope and clothing. The hallmark characteristic of Western Red Cedar, its natural durability, has preserved examples of this lifestyle for more than 100 years.
Growth and Harvest Regions
Western Red Cedar grows on the western edge of the coastal mountains from Southern Alaska to Northern California. Cedar typically grows in mixed forests with other species such as Douglas Fir, Pacific Coast Hemlock, Balsam Fir and Sitka Spruce. Forestry practices are guided by the internationally recognized sustainable forest management system elements of ISO 14001 as part of the CSA Z809 Canadian national standard. These high standards of sustainable forestry are audited by third party inspection agencies to insure compliance with the certification standards. Forest management plans control harvest levels and require reforestation to enhance natural regeneration and insure regional biodiversity.
Natural Durability
Western Red Cedar is one of the few wood species that are naturally at home in the outdoors. It is classified as a durable wood by the building codes across North America, which permits the use of its heartwood in exterior applications without preservative treatments. The heartwood contains extractive that are toxic to decay causing fungi. The two principal extractives that are responsible for the decay resistance are Thujaplicans and water soluble Phenolics. The tree’s ability to produce these extractives increases with age making the outer regions of heartwood the most durable. Mature Coastal Cedar that is rich in decay resistant extractives.
Dimensional Stability
Dimensional Stability is essential for a wood product to maintain its shape during its service life. This is especially true of products that are subjected to the climatic changes of exterior applications. Western Red Cedar has twice the stability of most commonly available conifers. The stability is a result of its low density and shrinkage factors. As a result, Cedar products shrink and swell minimally with changes in moisture. This superior resistance to warping, cupping and twisting makes them the best choice for use as sidings, decking, fencing and outdoor garden landscaping.
Density
At 22lbs/ft3 at 6% moisture content, Western Red Cedar is one of the lightest softwoods available. Its specific gravity is a low 0.33. the light weight is the result of a larger percentage of lower density early wood and less high density late wood within the annual growth rings. The lower density cells have air spaces that positively influence the insulating properties of the wood.
| Species |
Density (lbs/ft3) |
| Western Red Cedar |
22 |
| Douglas Fir |
31 |
Thermal Insulating Properties
Western Red Cedar is an excellent thermal insulator. The low density and presence of air spaces make it the best insulator of any available softwood. Its thermal conductivity factor K is 0.74 BTU in / ft2 h F and it’s R-value is 1.35 per inch of thickness. These exceptional thermal insulating properties protect a building from the extremes of heat and cold. Cedar Sidings provide far superior thermal protection to alternatives such as concrete, brick and stone.
Acoustic Properties
The open cell structure of Western Red Cedar has demonstrated an ability to absorb and dissipate sound energy. The cell structure converts the sound energy into heat by friction and viscoelastic resistance. The use of Cedar for walls and ceilings provides a level of sound insulation that will quieten rooms.
Flame Spread & Smoke Development Ratings
Western Red Cedar has flame spread and smoke development classifications that are superior to the minimums set by the building codes. These ratings permit Cedar to be used in many interior applications without treatment.The surface burning characteristics are used to regulate and control the rate of flame spread in case of fire. Lower ratings indicate more resistance to the spread of fire. The rating for Western Red Cedar has a class II rating of 69. This compares to Canadian and American code requirements of 150 and 200 respectively. The smoke development classification for Western Red Cedar is 98 which is less than the code specifications of 300 and 450 for Canada and US respectively.
Termite Resistance
The death rate of termites consuming Western Red Cedar varies with fibre source and the species of termites from 100% in several days to 40% in several weeks. Termites prefer food sources other than Western Red Cedar, however in the absence of alternative food sources, some termites will attack Western Red Cedar. It is best to consult local experts on their experience with Cedar’s resistance to the specie of termite that inhabits the region. In the absence of local knowledge it is recommended that preventative treatments be made to insure consistent resistance to attack in areas that are prone to termite attacks.
Workability
Western Red Cedar has a fine, straight grain and uniform texture that make it easy to cut, saw and nail with common tools. These features also contribute to its ability to be planed to a smooth surface or profiled to any pattern. Cedar is highly resistant to splitting caused by fasteners. It is suggested that screws be lengthened approximately 1/3 when specified for use with Cedar. Cedar’s freedom from pitch and resin make it an excellent base for all types of paints and stains.
Gluing Properties
The lack of pitch and resin allows Western Red Cedar to hold glue bonds from a wide range of adhesives. Fingerjointed Cedar Siding is an example of the application of this feature to create a highly desirable product.
Extractive Bleeding
Western Red Cedar contains water soluble extractives that contribute to its colour, durability and smell. The presence of moisture on exterior surfaces can bring these extractives to the surface and leave a reddish brown stain after the water has evaporated. The stains can be removed with detergent and water when they are first on the surface, however, they can be more difficult to remove after exposure to the sun. Controlling the extractive bleeding process is a matter of moisture control. When primers are required prior to the application of a solid colour coating, an oil primer is recommended because of its superior ability to block out moisture. This will limit the potential for extractive stains to appear on the coated surfaceRemoval of mature extractive bleeding stains is accomplished with an oxalic acid solution. Oxalic acid is available at most paint and hardware stores.
Iron Stains
The extractives in Cedar are also prone to staining when they are in contact with iron. The most common source of iron is the fasteners. The stain is a reaction to the water soluble polyphenols resulting in a blue-black blot or streak that follows the moisture pattern in the area of the iron sourceCare must be taken not to use wire brushes to clean Cedar or to allow iron fillings from other work projects to come into contact with Cedar. The use of common steel or electroplated fasteners will lead to staining. The solution to iron staining is to select fasteners made from stainless steel,aluminium or double hot dipped galvanized steel. Stainless steel fasteners are best and recommended for deck and siding applications where the fasteners are highly visible.
Other Species
NOTE: Cedar Sales are also stockists of Clear Grade Oregon, Merbau/Kwila,N.G. Rosewood, Surian, Malas and other species for more information enquire.
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