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INDOOR PRODUCTS | PROPERTIES
Resistance to Decay
Western Red Cedar heartwood is renowned for its high decay-resistance. This natural durability is attributed to the presence of extractives, mainly the thujaplicins, and to a lesser extent, the water-soluble phenolics which are toxic to a number of wood rotting fungi. Western Red Cedar has a durability Class 2 in Europe and Australia, the highest category for durability of any softwood listed. |
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Dimensional Stability
Western Red Cedar wood has excellent dimensional stability because of its low wood density and low shrinkage factor. A major contributor to this stability is the fact that its moisture content at the fibre saturation point is 18 to 23%, compared to 25 to 30% in most Canadian softwoods. As a result, Western Red Cedar shrinks and swells minimally, displaying only small movements with changes in humidity. Lower absorption of water is a result of the high extractive content blocking absorption sites. This property contributes to Western Red Cedar’s suitability for use in paneling, mouldings and a number of other applications such as saunas where dimensional stability and water repellency is important.
Thermal and Insulating Properties
Western Red Cedar has good insulation value because of its low wood density and coarse texture. It is the best insulator among the most common available softwood species and is far superior to brick, concrete and steel. This property ensures that homes built with Western Red Cedar will be cooler in the heat of summer and warmer in winter as opposed to homes using denser species or man-made products. Western Red Cedar’s ability to dampen vibrations is an important acoustical property which makes it particularly effective as paneling and moulding where it is desirable to reduce or confine ne noise.
Flame Spreading Rate
The flame-spread rating of Western Red Cedar is 67 to 73 (Class II rating) and the smoke developed classification is 98. Both of these are used to regulate the use of materials where potential to generate smoke or smoke control movement is important. Due to its low flame-spread rating, it will perform better than most dense softwoods which have flame-spread ratings around 100. Western Red Cedar has a flame spreading rate and a smoke-developed classification that are considerably below the maximum limits set by most building codes.
Finishing and Workability
The lack of pitch or resinous extractives that are soluble in paint vehicles contributes to Cedar’s good finishing properties. Cedar takes a variety of coatings, paints and stains exceptionally well, particularly when dried and properly primed. Western Red Cedar is among the easiest timbers to work with because of its straight grain and uniform texture. It planes and sands cleanly and, because of its low wood density, requires little energy to saw or otherwise work. Cedar also glues well with a wide range of adhesives and gluing conditions. |
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Q: What do you recommend for treatment of cedar siding?
— Mary, Kansas City, Missouri
A: Tom says: Cedar wood does contain a lot of tannic acids, especially red cedar, but in general, cedar doesn’t have to be treated that differently than other woods. But really I need to know whether you want to leave the cedar clear. If so, there are several excellent products out there for cedar siding and decks, which you should be able to find out about by consulting a professional at your local hardware store. One thing to remember is that you’ve got to make sure your cedar is clean and dry when you apply these finishes. On the other hand, if you want to paint the cedar siding, it’s got to first be primed, cleaned and prepped. As I said, the preparation is the most important step in any kind of painting you do: the surface has to be clean and dry. And depending on your situation, if you can get the cedar and let it weather a little bit, a lot of the tannic acids will come out, so it’ll be easier to paint. If not, and you painted it white for instance, sometimes the tannic acids will bleed through the white and that can be difficult to hide. A good primer followed by a latex top coat, or just a solid-body paint, or else a stain would be your best bets, being sure to follow the manufacturer’s recommendation on all.
